JP7381634B2 - Air pulse generator and its sound generation method - Google Patents

Description

The present application relates to an air-pulse generating device and a sound producing method thereof, and more particularly, to an air-pulse generating device and a sound producing method thereof, and more particularly, to increasing the overall air pulse rate and increasing the sound pressure level. The present invention relates to an air pulse generator and a sound generation method thereof that can be improved and/or save power.

Speaker drivers and rear enclosures are two major design challenges in the speaker industry. With conventional speakers, it is difficult to cover the entire audio frequency band, for example 20Hz to 20KHz. Both the radiating/moving surface and the back enclosure volume/size for a conventional loudspeaker are large enough to produce high-fidelity sound at a sufficiently high sound pressure level (SPL). is necessary.

Therefore, how to design compact sound producing devices while overcoming the design challenges faced by conventional speakers is an important goal in this field.

U.S. Patent Application No. 17/553,806 U.S. Patent Application No. 17/553,808

Therefore, the main object of the present application is to provide an air pulse generator and a method of sound generation thereof in order to improve over the drawbacks and/or limitations of the prior art.

One embodiment of the present invention provides an air pulse generator comprising: a membrane structure and a valve structure; a cover structure, wherein a chamber is formed between the membrane structure, the valve structure and the cover structure; an air wave oscillating at an operating frequency is formed within the chamber; the valve structure is configured to be actuated to perform an opening and closing operation to form at least one aperture; , connects the air inside the chamber with the air outside the chamber; the opening and closing operations are synchronized with the operating frequency.

Another embodiment of the invention provides a sound generation method applied to an air pulse generator, the method comprising the steps of forming an air wave in a chamber, the air wave vibrating at an operating frequency, is formed in the air pulse generator; forming at least one aperture in the air pulse generator at an opening frequency, the at least one aperture directing air within the chamber to the chamber; connecting with outside air; the open frequency is synchronized with the operating frequency.

These and other objects of the invention will become apparent to those skilled in the art after reading the following detailed description of the preferred embodiments illustrated in the various figures and drawings.

1 is a schematic diagram of an air pulse generator according to an embodiment of the present application; FIG.

1 is a schematic diagram of a plurality of waveforms according to an embodiment of the present application; FIG.

1 is a schematic diagram of a plurality of signals according to an embodiment of the present application; FIG.

3 illustrates a membrane drive signal according to one embodiment of the present application.

FIG. 2 is a schematic diagram showing a top view of the air pulse generator shown in FIG. 1;

1 is a schematic diagram of a cross-sectional view of an air pulse generator according to an embodiment of the present application; FIG.

1 is a schematic diagram of a cross-sectional view of an air pulse generator according to an embodiment of the present application; FIG.

1 is a schematic diagram of a cross-sectional view of an air pulse generator according to an embodiment of the present application; FIG.

1 is a schematic diagram of a cross-sectional view of an air pulse generator according to an embodiment of the present application; FIG.

9 is a schematic diagram of the air pulse generator shown in FIG. 8 disposed within an arrangement according to an embodiment of the present application; FIG.

9 is a schematic diagram of the air pulse generator shown in FIG. 8 disposed within an arrangement according to an embodiment of the present application; FIG.

1 is a schematic diagram of a mobile device according to one embodiment of the present application; FIG.

1 is a schematic diagram of a cross-sectional view of an air pulse generator according to an embodiment of the present application; FIG.

1 is a schematic diagram of a cross-sectional view of an air pulse generator according to an embodiment of the present application; FIG.

1 is a schematic diagram of a cross-sectional view of an air pulse generator according to an embodiment of the present application; FIG.

1 is a schematic diagram of valve movement according to an embodiment of the present application; FIG.

U.S. Patent No. 10,425,732 discloses a sound system that includes a plurality of air pulse generating elements capable of generating a plurality of PAM (Pulse Amplitude Modulated) air pulses at an ultrasonic pulse rate higher than the maximum human audible frequency. A generator or pneumatic pulse speaker (APPS) is provided. US Pat. No. 10,425,732 also discloses that an APPS can function as a fan that can be placed within an electronic device and can help dissipate heat of the electronic device.

U.S. Patent No. 10,771,893 discloses a SEAM ( single-ended amplitude modulation) drive signal. The SEAM drive signal includes a plurality of electrical pulses having the same polarity relative to (or with respect to) a constant voltage. For SEAM drive signals, each electrical pulse cycle includes a PAM (Pulse, Amplitude Modulation) phase and a RST (Reset) phase, as described below. The SEAM drive signal may be a PAM signal within the PAM phase and may return to a reset voltage within the RST phase.

U.S. patent application Ser. A sound generating device or APPS is provided in which the sound generating device or APPS propagates through a pressure injection orifice (PEO) formed on a membrane or plate of the sound generating device.

U.S. Patent No. 11,043,197 utilizes a membrane to compress/expand air within a chamber, temporarily opening an air shunt so that the pneumatic equilibration process between the two sides of the membrane is accelerated. The present invention provides an air pulsing element and APPS that utilizes slits formed on the membrane to form a virtual valve.

In one embodiment, the air pulse generator of the present application may be applied in APPS applications configured to generate PAM air pulses at ultrasonic pulse rates according to APPS sound generation principles. In another embodiment, the air pulse generator of the present application functions as a fan and can be applied in air movement or fan applications similar to US Pat. No. 10,425,732.

FIG. 1 is a schematic illustration of a cross-sectional view of an air pulse generator 890 according to one embodiment of the present application. Air pulse generator 890 may be applied within the APPS. Air pulse generator 890 includes membrane structure 12 , valve structure 11 , and cover structure 804 . A chamber 105 is formed between membrane structure 12, valve structure 11, and cover structure 804. Air pulse generator 890 produces its output at ports 707L and 707R. FIG. 1 shows the membrane structure 12 in a state in which the membrane structure 12 is (substantially) flat and parallel to the XY plane (solid outline) and in an operating state in which the membrane structure 12 is curved. (dotted outline).

The membrane structure 12 and the valve structure 11 may have a thin film structure, which is e.g. (electromechanical systems) manufacturing processes, but are not limited to these. In the embodiment shown in FIG. 1, membrane structure 12 includes a first membrane portion 102a and a second membrane portion 102b. Valve structure 11 includes a first valve portion 101 and a second valve portion 103. Cover structure 804 includes a top plate 804T and side walls 804L and 804R. Chamber 105 is surrounded by/between membrane sections 102a and 102b, valve sections 101 and 103, top plate 804T, and side walls 804L and 804R. Valve portion 101/103 is fixed at one end to support structure 110/115 and free to move at the other end, with the free moving end located proximate/adjacent to sidewall 804L/804R.

Membrane structure 12 is configured to be actuated such that air waves AW are generated. Furthermore, by carefully selecting the drive signal(s) provided to the membrane structure 12, the air wave AW oscillates at the operating frequency f _CY and is caused to oscillate within the chamber 105 in a direction parallel to the membrane structure 12 (e.g. direction).

From a certain point of view, an air wave is defined as an air wave in which the mass of air molecules changes in the front-back direction (for example, from the perspective of the movement of the X-axis component, left and right in the Can be associated with periodic movement. An air wave that oscillates at a specific frequency is related to an operating frequency f _CY where the specific frequency is the reciprocal of the specific period, and vice versa.

Valve structure 11 is configured to operate to perform opening and closing operations at an opening frequency to periodically form at least one aperture, the at least one aperture causing air within chamber 105 to flow into the surrounding air. It is connected to the air outside the chamber 105. Specifically, the valve portion 101 may be actuated to form-and-unform the opening 112 (in the Z direction) and move up and down (in the Z direction), which is referred to as opening and closing the valve 101 . Similarly, the valve portion 103 can be actuated to perform up and down movement (in the Z direction) causing and not forming the opening 114, which is referred to as opening and closing the valve 103. The opening and closing operation (or opening frequency) of the valve structure 11, including the valves (parts) 101 and 103, is synchronized with the air wave AW, which in turn is synchronized with the operating frequency f _CY . The opening and closing operations of the valve structure/section are synchronized with the operating frequency f _CY , which means that the opening and closing operations of the valve section/structure are (preferably) performed at the operating frequency f _CY or (M/N)*f _CY . where M and N are both integers. The opening/closing, up/down, forming and non-forming movements will be explained in detail later. In the following description, valves 101/103 may be referred to as valve portions 101/103 for brevity.

The function of the valve opening is similar to that of a variable resistance in which the resistance to airflow Z _VALVE is controlled by the valve opening. When the valve is closed, ie, Z101<Z _O/C or Z103<Z _O/C , the magnitude of Z _VALVE is high (Hi-Z). When the valve is open, that is, Z101>Z _O/C or Z103>Z _O/C , the magnitude of Z _VALVE is inversely proportional to the opening degree, or Z101-Z _O/C and Z101-Z _O/C. do. The wider the valve opens, the lower the value of Z _VALVE and the higher the air flow rate for a given chamber pressure.

chamber resonance

Note that the air waves AW generated by the membrane structure 12 may include incident waves and reflected waves, given that side walls 804L and 804R may function as reflective walls. In one embodiment, the width of chamber 105, shown as W ₁₀₅ , or the distance between sidewalls 804L and 804R, is designed such that the incident and reflected waves can be collected and formed into a standing wave within chamber 105. can be done.

In one embodiment, the distance or width W ₁₀₅ between sidewalls 804L and 804R may be equal to an integer multiple of a half wavelength (λ/2) corresponding to the operating frequency f _CY of the air wave AW, where λ=C/ f _CY , C is the speed of sound.

In one embodiment, the distance or width W ₁₀₅ between sidewalls 804L and 804R is such that first order ( ^1st ) mode (or n=1 mode) resonance, also referred to as fundamental mode resonance or first harmonic resonance, occurs within chamber 105. It can be designed to be formed into In this case, only one air-motion antinode (with amplitude reaching a peak) is present in chamber 105 (possibly in the center of chamber 105); two air-motion nodes (with amplitude reaching 0 only one pneumatic node is located within the chamber 105 (which may be located in the center of the chamber 105); only two pneumatic antinodes are located on the side walls 804L and 804R Located in

Here, in terms of chamber resonance or standing waves, the antinode of air motion represents the position where the velocity/displacement amplitude of air molecules reaches a maximum in the air motion across the X-axis within the chamber; the node of air motion is: Represents the position where the amplitude of the velocity/displacement of an air molecule reaches a minimum in air motion across the X-axis within the chamber (usually zero motion); The air pressure node represents the position where the amplitude of the air pressure fluctuation reaches a minimum in air pressure across the X-axis within the chamber.

In FIG. 1, the curve U102 schematically represents the displacement of air particles distributed in the X direction at different times, and the curve W102 schematically represents the pressure distribution in the chamber at different times. For example, the dashed line of curves U102 and W102 corresponds to time _t0 , and the solid line of curves U102 and W102 corresponds to time _t1 . P0 in FIG. 1 may refer to ambient pressure, which may be 1 atmosphere. In one embodiment, to achieve first-order mode (or n=1 mode) resonance, the distance or width W ₁₀₅ between sidewalls 804L and 804R is half a wavelength corresponding to the operating frequency f _CY of the air wave AW. (λ _CY /2).

Further details of the 101/103 valve movement are shown in FIG. At time t ₀ (or when t=t ₀ ), valve 101 is actuated to bend upward such that aperture 112 is opened or formed, and valve 103 (substantially) seals aperture 114 This means that the opening 114 is closed or not formed, as shown at the top of FIG. On the other hand, at time _t1 (or when t= _t1 ), valve 101 may be actuated to (substantially) seal aperture 112, which means that aperture 112 is closed or not formed. This means that the valve 103 is actuated to bend upward so that an opening 114 is opened or formed, as shown at the bottom of FIG. In one embodiment, at some point in time t ₂ (or t=t ₂ , where t ₂ ≠t ₀ and t ₂ ≠t ₁ ), valves 101 and 103 open opening 112 and 114 is hardly opened or hardly closed, which corresponds to Z101=Z _O/C and Z103=Z _O/C , respectively, as shown in FIG.

FIG. 2 is a schematic diagram of multiple waveforms according to one embodiment of the present application. Waveform Z101 schematically represents the displacement of the free moving end of valve portion 101 in the Z direction; while waveform Z103 schematically represents the displacement of the free moving end of valve portion 103 in the Z direction. Z _O/C represents a level of displacement, and the suffix O/C represents the line separating the open and closed states. If the displacement of the free moving end of the valve Z101 is greater than (above) the displacement level Z _O/C , an opening 112 is formed or the valve 101 is opened. If the displacement of the free moving end of the valve Z103 is greater than the displacement level Z _O/C , an opening 114 is formed or the valve 103 is opened. If the displacement of the free moving end of the valve Z101 is less than (below) the displacement level Z _O/C , no opening 112 is formed or the valve 101 is closed. If the displacement of the free moving end of the valve Z103 is less than the displacement level Z _O/C , the opening 114 is not formed or the valve 103 is closed.

Waveform P112 schematically represents the air pressure at opening 112 (inside chamber 105). Waveform P114 schematically represents the air pressure at opening 114 (inside chamber 105). Waveform Z102a represents the displacement of membrane portion 102a, which may share a similar waveform with P112. Waveform Z102b represents the displacement of membrane portion 102b, which may share a similar waveform with P114. Waveform P707L schematically represents air pressure (or a quantity similar to air pressure) at port 707L (outside chamber 105). Waveform P707R schematically represents air pressure (or a quantity similar to air pressure) at port 707R (outside chamber 105). Waveform P890 represents the sum/superposition of P707L and P707R and corresponds to the aggregated on-axis output acoustic pressure of device 890. Waveforms Z102a/Z102b having lengths such as μM generally have different amplitudes than waveforms P112/P114 having units of pressure such as Pa. However, since the purpose of FIG. 2 is primarily to illustrate the timing relationships between different parts of the operation, these waveforms are merged into FIG. 2 for simplicity.

FIG. 3 is a schematic diagram of a plurality of signals according to one embodiment of the present application. S _IN represents the input audio signal. S101/S103 represents a valve drive signal configured to drive valve portions 101/103. S102a/S102b represents membrane drive signals configured to drive membrane portions 102a/102b.

AM modulation waveform

As can be seen from the plots/waveforms P112 and P114 in FIG. can be done. The carrier component, typically expressed as cos(2πf _CY t), oscillates at an operating frequency f _CY where f _CY = 1/T _CY , where f _CY indicates the operating cycle. The modulation component, denoted as m(t), is reflected by the envelope (shown as a dotted line in FIGS. 2 and 3) of the amplitude modulation waveform corresponding to the input audio signal S _IN . In one embodiment, the modulation component m(t) may correspond to or be proportional to the input audio signal S _IN .

Amplitude modulated waveforms P112/P114 may be achieved by driving membrane structure 12 with a pulsed amplitude modulated drive signal. For example, membrane drive signals S102a/S102b shown in FIG. 3 that drive membrane portions 102a/102b are pulse amplitude modulated signals generated according to input audio signal S _IN .

Membrane drive signal

In other words, the membrane drive signal S102a includes a first pulse amplitude modulated signal that includes a plurality of first pulses for a particular bias voltage _VB . The first pulses are distributed/arranged in time by the operating frequency f _CY . Similarly, membrane drive signal S102b includes a second PAM signal that includes a plurality of second pulses relative to bias voltage _VB . The second pulses are distributed/arranged in time by the operating frequency f _CY .

Additionally, the first pulse includes a first transition edge; while the second pulse includes a second transition edge. The first transition edge of the first pulse in PAM signal S102a coincides with the second transition edge of the second pulse in PAM signal S102b. Further, at a coincidence time of the first transition edge and the second transition edge, the first transition edge corresponds to a first transition polarity, and the second transition edge corresponds to a second transition polarity. corresponds to The first transition polarity is opposite to the second transition polarity at certain coincident times. Details of the coincidence of the first and second transition edges and the opposite polarity of the first and second transitions may be found in FIG. 3 of this application or in U.S. Pat. No. 11,043,197 or U.S. Pat. reference may be made and these are not described herein for brevity.

Note that the membrane drive signals S102a/S102b that drive the membrane portions 102a/102b are bipolar (or double-ended) with respect to the bias voltage _VB , but are not limited thereto. For example, FIG. 4 shows a second type of membrane drive signals S102a' and S102b'. Membrane portions 102a and 102b may be driven by membrane drive signals S102a' and S102b', respectively. Note that membrane drive signals S102a' and S102b' are SEAM drive signals that are unipolar with respect to bias voltage _VB . Similar to the monopolar membrane drive signals S102a and S102b, the first pulse in the drive signal S102a' and the second pulse in the drive signal S102b' are interleaved with each other, as shown in FIG. have simultaneous transition edges and opposite transition polarities. Details of the unipolar SEAM drive signal can be found in US Pat. No. 10,771,893, which is not discussed here for brevity.

FIG. 4 also shows a third type of membrane drive signal S102a'' (bottom solid line) and S102b'' (bottom dashed line, S102a''). In one embodiment, the membrane portion 102a is the membrane drive signal S102a'' _The membrane portion 102b may be driven by the membrane drive signal S102b''. In other words, the sum of the membrane drive signals S102a" and S102b" can be a constant. The constant is equal to the voltage level V _B (if Equation 1 is applied ) or 0 V (if Equation 2 is applied). Similar to the membrane drive signals S102a and S102b, the first pulse in the drive signal S102a" and the second pulse in the drive signal S102b" are simultaneously (coincidence) transition edges and opposite transition polarities, which can be observed from FIG.

pressure gradient

In one aspect, during a first interval (which may be the first half of the operating cycle T _CY ), the membrane drive signal pair (S102a, S102b)/(S102a', S102b')/(S102a'', S102b ”) to membrane portions 102a and 102b, membrane portion 102a may be actuated to move in the positive Z direction and membrane portion 102b may be actuated to move in the negative Z direction. Thus, during a first interval, membrane portion 102a may be actuated to compress a first portion/volume 105a (the top of membrane portion 102a) within chamber 105, and membrane portion 102b may be actuated to compress a first portion/volume 105a (top of membrane portion 102a) within chamber 105. may be actuated to inflate the second portion/volume 105b (above the membrane portion 102b) of the membrane portion 102b, such that a first pneumatic gradient is created from the first portion/volume 105a towards the second portion/volume 105b. (indicated by block arrow 116 in FIG. 1) is formed.

Conversely, during a second interval (which may be the second half of the operating cycle T _CY ), membrane portion 102b may be actuated to move in the positive Z direction and membrane portion 102a may be actuated to move in the negative Z direction. can be operated to move to. Thus, during the second interval, membrane portion 102b may be actuated to compress the second portion/volume 105b and membrane portion 102a may be actuated to expand the first portion/volume 105a. , so that a second pneumatic gradient (opposite of 116, not shown in FIG. 1) may be created from the second portion/volume 105b toward the first portion/volume 105a.

The pressure gradient direction of the air pressure gradient (eg, 116 shown in FIG. 1) generated by the membrane structure 12, including membrane portions 102a and 102b, is parallel to the X direction shown in FIG. The propagation direction of the air wave AW propagating within the chamber 105 is also parallel to the X direction. That is, the pressure gradient direction is parallel to the air wave propagation direction. In addition, the pressure gradient direction, which is parallel to the X direction, is perpendicular to the membrane displacement direction of the membrane structure 12, primarily in the Z direction, where the membrane displacement direction refers to the direction in which the membrane is actuated to move. . Therefore, the pressure gradient direction is parallel to the XY plane, the plane of the membrane structure, and orthogonal to the direction of membrane displacement (Z). By considering the membrane structure to be actuated or deformed, the pressure gradient direction (generated by the membrane structure) may be substantially parallel to the membrane structure and/or substantially parallel to the direction of membrane displacement/movement. can be considered perpendicular to/orthogonal to.

Spatial position of valve opening

When a standing wave is formed within the chamber 105, it is suggested that the aperture(s) be located at or near the pneumatic antinode(s) of the standing wave to increase audio output efficiency. Ru. For air pulse generator 890, an aperture may be formed spatially at a location where the air/standing wave peak is achieved, where the air/standing wave peak is (for APPS applications) It can be in terms of air pressure.

For APPS, assume that the air pressure in the chamber can be expressed as a single-variable function p(x) or a two-variable function p(x,t), where x indicates the variable in the X-axis and t is Shows variables on the time axis. The peak is located where the first (partial) derivative is zero, i.e. dp(x)/dx=0 or ∂p(x,t)/∂x=0 (to find the optimal spatial position of the valve opening) ). In other words, a peak (for some fixed time t ₀ ) can be interpreted as a local maximum or minimum value of p(x)/p(x,t ₀ ) across the X-axis.

In this case, for the air pulse generating APPS device 890, the antinode of the air pressure of the standing wave is located at the side walls 804L and 804R, so the openings 112 and 114 are formed near the side walls 804L and 804R.

Temporal alignment of valve opening

In another aspect, to increase the efficiency of air pulsing, the valve opening(s) may be closed during the interval during which the peak pressure of the air wave is achieved at the location of the valve opening, as shown at 112 and 114 in FIG. It is suggested that timing is formed. Peak pressure timing in this specification assumes that the air pressure in the chamber can be expressed as a single-variable function p(t) or as a two-variable function p(x,t), with the first (partial) time derivative being zero. , i.e. dp(t)/dt=0 or ∂p(x,t)/∂x=0 (to find the optimal timing of valve opening, ie the temporal behavior). In other words, (for some fixed position x ₀ , x ₀ may be the position of the valve opening 112 or 114) the peak is the local maximum of p(x)/p(x ₀ , t) over the t-axis. or can be interpreted as a local minimum.

For example, referring to FIG. 2, the time interval during which opening 112 is formed (i.e., valve portion 101 is actuated open or valve 101 is opened) is shown as the dotted area in plot Z101. the time interval during which opening 114 is formed (ie, valve portion 103 is actuated or valve 103 is opened) is shown as a cross-hatched area within plot Z103. Aperture 112 is formed during a (first) interval _T1 ; whereas aperture 114 is formed during a (second) interval _T2 . Both intervals T ₁ and T ₂ are within the operating cycle T _CY , meaning T ₁ ≦T _CY , T ₂ ≦T _CY and T ₁ +T ₂ ≦(1+d)×T _CY , where T _CY =1/f _CY and d<0.5.

To improve efficiency, the first aperture 112 is formed within a first interval T ₁ during which a first peak pressure pk ₁ of the air wave AW at a first location (corresponding to side wall 804L) is achieved; the second opening 114 is formed within a second interval T ₂ during which a second peak pressure pk ₂ of the air wave AW at the second position is achieved.

In one aspect, the opening frequency of valves 101 and 103 is equal to the operating frequency f _CY in the embodiment shown in FIG.

Note that in the embodiment shown in FIG. 2, the first interval T ₁ (representing the opening interval of valve 101) covers half of the operating cycle T _CY , and the second interval T ₂ (representing the opening interval of valve 103) ) covers another half of the working cycle T _CY , which means that T ₁ = T ₂ ≈ T _CY /2 (i.e., the length of the interval T _y is reduced by half the length of the working cycle T _CY , it means that T _y ≒ T ₁ or T _y ≒ T ₂ ), but is not limited thereto. The interval T ₁ or T ₂ may be slightly shorter or longer than T _CY /2 (eg, within ±10% or ±20%). As long as the opening interval of valve 101 covers the first peak pk ₁ and the opening interval of valve 103 covers the second peak pk ₂ , the requirements of this application are met and this is within the scope of this application .

Furthermore, the first interval T ₁ (representing the opening interval of the valve 101) is a first overpressure/negative _pressure (over /under-pressure) interval, the first over-pressure/under-pressure interval overlapping with T ₁ in the embodiment shown in FIG. Similarly, a second interval T ₂ (representing the opening interval of valve 103) indicates that the air pressure P114 generated by the movement of the membrane is equal to or smaller than a certain pressure P _th during a second overpressure/negative pressure. The second overpressure/underpressure interval overlaps T ₂ in the embodiment shown in FIG. 2 . In this case, the air pulse generator 890 generates positive/negative air pulses during valve opening intervals T ₁ and T ₂ , where the positive/negative air pulses are within the valve opening interval(s). may be propagated from chamber 105 to the surroundings during this period.

The AW pressure wave generated by the drive waveforms S102a'/S102b' in FIG. 4 is a simple AM, and the AW pressure wave generated by the drive waveforms S102a/S102b in FIG. 3 or S102a"/-S102a" in FIG. Note that DSB-SC (double-sideband, suppress carrier). The timing relationship shown in FIG. 2 corresponds to a simple AM modulated AW pressure wave, where the peaks pk ₁ , pk ₂ do not cross the line of P _th . However, for the DSB-SC modulated AW pressure wave, pk ₁ , pk ₂ crosses the line of P _th whenever the polarity of S _IN changes, then the overpressure becomes negative pressure and vice versa. It is.

Note that the total pressure in the chamber can have two component pressures: one caused by the movement of the membrane and the other caused by the movement of the valve. Both components may be in the form of standing waves. The pressures P112 and P114 shown in FIG. 2 refer only to component pressures caused by membrane movement.

Synchronous valve open

Further, the valve portion 101 may define an opening 112 within or between a plurality of first valve opening intervals, such that the air pressure P112 is greater than a particular pressure P _th within or during a plurality of first overpressure intervals. obtain. In the embodiment shown in FIG. 2, the plurality of first valve opening intervals (of valve 101) and the plurality of first overpressure intervals (of pressure P112) are aligned or overlapped in time and the first The valve opening interval (of valve 101) and the first overpressure interval (of pressure P112) are annotated as _T1 in FIG.

Similarly, the valve portion 103 may define an opening 114 within or between the plurality of second valve opening intervals, and the air pressure P114 may be greater than a particular pressure P _th within the plurality of second overpressure intervals. . The plurality of second valve opening intervals (of valve 103) and the plurality of second overpressure intervals (of pressure P114) may also be aligned or overlapped in time; The pressure interval (of pressure P114) is annotated as _T2 as in FIG.

In this application, a plurality of first time intervals and a plurality of second time intervals are temporally aligned or overlapped, which means that 1) the plurality of first time intervals and the plurality of second time intervals are arranged in time (or appear in time) at the same frequency; or 2) the first time interval and a second time interval that overlaps with the first time interval form an overlapping region. However, it may refer to the length of the overlapping region being at least 50% of the length of the first (or second) time interval.

By aligning the valve opening interval and the overpressure interval, air pulse generator 890 generates a plurality of first air pulses AP ₁ (shown as P707L in FIG. 2 in FIG. 2) at port 707L through opening 112. ) and, via opening 114, a plurality of second air pulses AP ₂ (shown as P707R in FIG. 2) at port 707R. In addition, the times corresponding to the peak valve openings of Z101/Z103 are preferably aligned to the times corresponding to the peak pressures of P112/P114 generated by membrane transport.

From a different point of view, T ₁ in FIG. 2 are respectively: the first valve opening interval of the valve 101 (the point of view of Z101); from the volume 105a onto the membrane portion 102a, towards the volume 105b and onto the membrane portion 102b; a first membrane displacement interval in membrane sections 102a (from the perspective of Z102a) and 102b (from the perspective of Z102b) creating a pressure gradient (vector) directed toward; a first overpressure interval (from the perspective of P112); and a first overpressure interval (from the perspective of P112); 1 air pulse AP ₁ may refer to the 1 first duty period. Similarly, T ₂ in FIG. 2 are, respectively: the second valve opening interval of valve 103 (in terms of Z103'); from volume 105b, over membrane portion 102b, towards volume 105a, over membrane portion 102a; a second membrane movement interval of membrane portion 102a (perspective view of Z102a') and membrane portion 102b (perspective of Z102b') creating a pressure gradient (vector) directed toward; a second overpressure interval (perspective of P114'); and the second duty period of the second air pulse AP ₂ at port 707R.

FIG. 2 shows a first valve opening interval of valve 101, a first chamber pressure gradient interval, movement of membrane portions 102a and 102b, a first overpressure interval and a first duty period of first pneumatic pulse _AP1 . are temporally aligned (peak-to-peak) and overlapping (periodic). Similarly, a second valve opening interval of valve 103, a second chamber pressure gradient interval, movement of membrane portions 102a and 102b, a second overpressure interval (in terms of P114'), and a second pneumatic pulse AP ₂ The second duty periods of are temporally aligned (peak-to-peak) and overlapping (periodic).

Combining two half-wave rectified pulses into one full-wave rectified pulse

In one aspect, by comparing waveforms P112 and P707L, P707L can be interpreted as a half-wave rectified version of P112, rectified by the timing variation impedance associated with movement Z101 of valve 101. Also, by comparing waveforms P114 and P707R, P707R can be interpreted as a half-wave rectified version of P114 rectified by the timing variation impedance associated with movement Z103 of valve 103. Waveform P890, which adds waveforms P707L and P707R and represents the on-axis output sound pressure of device 890, can be interpreted as a full-wave rectified version of P112 or P114.

Referring to plot P707L, a plurality of first air pulses AP ₁ are generated at a first (air) pulse rate APR ₁ corresponding to the operating frequency f _CY . Referring to plot P707R, a plurality of second air pulses AP ₂ are generated at a second (air) pulse rate APR ₂ corresponding to the operating frequency f _CY .

Referring to plot P890, the first plurality of air pulses AP ₁ and the second plurality of air pulses AP ₂ are temporally and interleaved with each other such that the air pulse generator 890 generates a plurality of aggregate air pulses. (aggregated air pulses) can be interpreted as generating an AP. The plurality of aggregate air pulses AP includes a first air pulse AP ₁ having a first pulse rate APR ₁ and a second air pulse AP ₂ having a second pulse rate APR ₂ . Aggregate air pulses AP are generated at an overall (air) pulse rate PRO.

Under the condition of APR ₁ =APR ₂ =f _CY as in the embodiment shown in FIG. 2, the overall pulse rate PRO is twice the pulse rate APR ₁ (or APR ₂ ). In other words, the overall pulse rate PRO corresponds to twice the operating frequency f _CY , i.e. PRO = 2*f _CY , where a 60 Hz 110 VAC sine waveform becomes a 120 Hz half sine waveform after full wave rectification. generate. similar to that.

Analogy with AM radio demodulation

In one respect, the effect of membrane movement can be compared to an AM radio station that generates EM waves that are amplitude modulated by a sound signal and radiates the AMEM waves into the atmosphere. Instead of EM waves, device 890 generates amplitude modulated ultrasound waves and transmits such AM ultrasound waves to chamber 105. Such ultrasound waves are further amplified by the standing wave construct of chamber 105 at the location of the valve. The standing wave structure of chamber 105 is similar to an EM waveguide where signal strength is maximized by placing ports at the node(s) and antinode(s) of the waveguide. The signal received at the valve location is then demodulated by the periodic operation of the valve(s), similar to a synchronous local oscillator in an AM receiver, and the nonlinear characteristics of the Z _VALVE , similar to a mixer in an AM receiver. and generates outputs P707R/P707R by dividing P112/P114 by its corresponding valve impedance Z _VALVE (t).

As an example, assuming that the plots Z101, P112, Z103, and P114 are sinusoids for simplicity, i.e., the interleaved drive signals S101, S103 result in Z101∝sin(ωt), Z103∝−sin( In the example shown in Fig. 1, due to the n=1 standing wave, there is a phase reversal between P112 and P114, so these two local pressures are ∝S _IN · sin( ωt), P114∝−S _IN ·sin(ωt), where the negative sign “−” represents a phase difference of 180°, and ω=2πf _CY . Assuming Z _VALVE ∝1/(Z101-Z O/ _C ) if Z101>Z _O/C and Z _VALVE = ∞ otherwise, P707L is P707L∝S _IN when Z101>Z _O/C - sin ² (ωt), otherwise it can be expressed as P707L=0. Similarly, P707R can be expressed as P707R∝S _IN · sin ² (ωt) if Z103>Z _O/C and P707R=0 otherwise. Quantity P890 is P707L+P707R and represents the audio sound produced by device 890. After replacing P707L and P707R, we obtain P890=P707L+P707R∝S _IN ·sin ² (ωt) for all the times that device 890 operates.

When a DSB-SC AM radio waveform with a mathematical representation of S _IN sin(ωt) is demodulated by a carrier signal sin(ωt) generated by a synchronous local oscillator using a multiplier, the result is , S _IN・sin(ωt)・sin(ωt)=S _IN・sin ² (ωt), and it should be noted that this is exactly the same mathematical formula as P890 derived in the above paragraph. .

As is known to those skilled in the art, after multiplying the AM modulated signal/waveform S _IN ·sin (ωt) by the demodulated signal sin (ωt), the resulting signal (i.e., S _IN ·sin ² (ωt) ) is in the baseband, and 1/3 of the energy of the resulting signal is on a frequency band centered on twice the carrier frequency, ie 2·ω or 2·f _CY . As an example, it is assumed that P890∝S _IN ·sin ² (ωt)=S _IN ·(1/2−1/2cos(2ωt)) (Equation 3). The first term in Equation 3, 1/2·S _IN , represents the demodulated component on the baseband; on the other hand, the second term in Equation 3, 1/2·S _IN ·cos(2ωt), represents the demodulated component on the baseband. Represents the components of a sound wave band. As can be seen from Equation 3, the first energy of the first term in baseband is twice the second energy of the second term. As used herein, baseband refers to the frequency band of the input audio signal S _IN , which baseband covers/overlaps the human audible frequency band.

In FIG. 1 (or FIG. 6), the material of the oxide substrate under the valve 101/103, the membrane portion 102a/102b, may be removed by a photolithographic process/processes, and the support 110 and wall 111 are formed. obtain. According to a very fine line pattern, the Si or POLY layer(s) can be etched to form openings/slits. Such slits form a free moving end on the valve 101/103 (e.g. these slits may form an opening 112/114 when the displacement of the free moving end of the valve exceeds Z _O/C ). Alternatively, the slits can increase the compliance of the membrane portions 102a/102b (eg, by forming slits 113a, 113b on the membrane portions 102a/102b).

FIG. 5 is a schematic diagram showing a top view of the air pulse generator 890 shown in FIG. The air pulse generator 890 may (optionally) include cross linked beams 871, 872, disassembling the (long) valve 101/103 or the (long) membrane section 102a/102b into short pieces and supporting the support 110. and reinforce 891. The air pulse generator 890 may (optionally) have a slot 873, which connects one slit on the membrane portion to act as an air passageway to allow pressure to be released. It can be formed by spreading. Here, the slit generally has a width corresponding to the etching resolution of the MEMS manufacturing process, for example 0.5-1.8 μM across a 3-7 μM thick Si film; means line geometry width that is not limited by limits.

harmonic

Harmonic resonances can occur in air pulse generators. For example, FIG. 7 is a schematic illustration of a cross-sectional view of an air pulse generator 850 according to one embodiment of the present application. In the air pulse generator 850, the width W ₁₀₅ between sidewalls 804L and 804R is one wavelength (λ) corresponding to the operating frequency f _CY to achieve second-order mode (or n=2 mode) resonance. It can be. For second-order mode resonance, two air-motion antinodes are present within chamber 105 (e.g., one quarter (1/4) of width W ₁₀₅ from either side wall 804L or side wall 804R). three air-motion nodes are located near the center of chamber 105 and side walls 804L, 804R; two air pressure nodes are present within chamber 105 (e.g., at either three pneumatic antinodes are located at the center of the chamber ₁₀₅ and at the side walls 804L, 804R); Curve W102, which schematically represents the pressure distribution within chamber 105 over time, may result from movement of membrane portions 102c and 102d of air pulse generator 830 and may be symmetrical about centerline 703. When a standing wave of n=2 modes is formed in the chamber 105 of the device 850, as shown at W102 in FIG. As a result, the air pressure waveforms near the side walls 804L and 804R become in phase with each other, and a phase-inverted air pressure waveform with a similar amplitude is generated at the center of the chamber 105. Therefore, the antinode of the air pressure is in the chamber 105 (or width W ₁₀₅ ). , the valve opening 112 of the air pulse generator 850 may be located at/near a central location between the sidewalls 804L and 804R. In other words, harmonic resonance (i.e., n≧2) In addition to next to sidewalls 804L and 804R, the opening of the air pulsing orifice(s) may be at/near any air pressure antinode between the two sidewalls causing resonance.

The same description in the immediately preceding paragraph is also applicable to apparatus 830 of FIG.

In an air pulse generating device such as device 830 of FIG. 6, device 850 of FIG. 7, or device 890 of FIG. 1, demodulating operation of valves 101 and 103 produces pulses of airflow that accumulate over successive pulses; This causes a change in the net air mass within the chamber 105 over time, increasing/decreasing the pressure P0 within the chamber 105. Since such back pressure reduces the output SPL, it is suggested to release such pressure.

In the case of the air pulse generator 830 of FIG. 6, the slit openings 113a*/113b* may be designed to be close to a pneumatic node located W ₁₀₅ /4 away from the sidewalls 804L/804R. Due to the audio filter effect of the pneumatic node of the n=2 standing wave, the enlarged slit 113a*/113b* demodulates the valves 101 and 103 as indicated by the valve opening 112, as indicated by the waveform W102 across P0. The operation of device 830 is minimally affected while releasing pressure build-up due to operation.

For the air pulse generator 850 of _{FIG .} Contains 2 single pieces. In contrast to the situation in device 830, where membranes 102c, 102d are each composed of two sub-parts separated by slits 113a ^* and 113b ^* , in device 850 , membranes 102e and 102f are allowed to move freely. Since the slits 112 and 114 are located at the antinode of air pressure within the chamber 105 of the device 850, the width of these slits should be minimized to suppress air pressure leakage. Accordingly, one or more vents 713T can be created on the top cap at the pneumatic node location, eg, at a distance W ₁₀₅ /4 away from sidewalls 804L and 804R. In theory, one such vent would be sufficient for backpressure relief purposes, but to allow for optimal balance of air pressure within chamber 105, a pair of vents, as shown in FIG. It is preferable to arrange the vent 713T in a central mirror manner.

For the air pulse generator 890 of FIG. join together. Accordingly, the vent openings 713T on the top plate located at or near the pneumatic nodes are designed to allow airflow to pass through, as indicated by the alignment of the pneumatic profile W102 to the position where it passes through P0. The pressure rise caused by the demodulation operation of valves 101 and 103 is released.

The length and width of vent opening(s) 713T may be adjusted to form a suitable acoustic low pass filter (LPF) with the volume of chamber 105. The location of the vent opening(s) 713T may be at the antinode(s) of the air pressure relative to the operating frequency f _CY , where the amplitude of the frequency component corresponding to the standing wave is approximately zero. As a result, an acoustic notch filter is formed and the pressure corresponding to the amplitude modulated standing wave may be suppressed near/at the vent opening(s) 713T in the chamber 105, such that only pressure changes due to the demodulation operation occur at the vent opening. (Multiple) may exist near/there 713T. For devices operating at second-order mode resonance (e.g., device 850), the air pulse vent opening 713T is from either sidewall 804R and 804L, which is different from the device operating at first-order mode resonance (e.g., device 890). The vent opening 713T (of the air pulse generator 890) may be located approximately one quarter of the width W ₁₀₅ (W ₁₀₅ /4), where the vent opening 713T (of the air pulse generator 890) is near the midpoint between the two side walls 804R and 804L. obtain.

The structure of air pulse generator 850 may be modified according to different design considerations. For example, membrane 102e/102f may have two membrane sub-parts, or two pieces, such as, but not limited to, membranes 102a/102b or 102c/102d. The maximum Z-direction displacement of a one-piece membrane structure such as 102e/102f in FIG. Please note that there is. In contrast, in a two-piece per membrane structure, such a limit on Z-direction membrane displacement does not exist, as the two sub-parts always move in tandem, and larger displacements may be possible, thus , leading to improved unit-device-area effectiveness (SPL/m).

Furthermore, valve portions 101 and 103 shown in FIG. 7 may be considered virtual valves. In other words, the slit formed between the valve parts 101 and 103 can become a temporarily formed/opened valve opening (112') when the valve parts 101 and 103 are fully actuated. In addition, the temporarily formed/opened valve openings are formed periodically. When the aperture is opened, the chamber and the surrounding environment are connected through the aperture (112'). When the aperture is not open, the air flowing through the slit is negligible or below a threshold. Details of virtual valves (temporarily formed openings) can be found in US Pat. No. 11,043,197, which is not discussed here for brevity.

Additionally, similar to the device 890 shown in FIG. 1, a pressure gradient is also created within the device 850 through membrane movement and the nature of standing waves. Unlike device 890, membrane portions 102e and 102f are actuated to move in an in-phase manner, such that at a given time, both membrane portions 102e and 102f are actuated to move upwardly (or downwardly). refers to In this case, the pressure gradient is also established by exploiting the properties of n=2 standing waves. Similar to the description of FIG. 1, in FIG. 7, the dashed line of curves U102 and W102 corresponds to time _t0 , and the solid line of curves U102 and W102 corresponds to time _t1 . At time _t0 , membrane portions 102e and 102f are actuated to move upward (positive Z direction) and a pressure gradient is generated inward (X direction) as indicated by the dashed slope of W102. do. At time _t1 , membrane portions 102e and 102f are actuated to move downward (negative Z direction) and a pressure gradient is generated outward (X direction) as shown by the solid slope of W102. do. Similarly, the direction of membrane movement is substantially perpendicular to the direction of the pressure gradient.

Air movement or fan applications

The structure/mechanism of devices 890/830/850 can be refurbished/adapted for air movement or fan applications. Unlike sound waves, which travel at the speed of sound C, air motion, like that of wind, is a flow of air that is related to the motion of air particles, and the membrane portions 102a-102d/ of the air pulse generator 890/830/850 102, caused by a displacement of the membrane portion(s). In air moving or fan applications/modes of these devices, air particles within the device may be described primarily according to hydrodynamics or aerodynamics; in contrast, in air pulse (APPS) generating applications/modes of these devices, The behavior of the air within the device can be described primarily according to acoustics.

For air movement or fan applications, valve openings, such as openings 112 and 114 shown in apparatus 890/830/850, are spaced in space and temporally in time so that air movement is maximized. The peak of air movement may be in terms of velocity of air moved or volume of air moved.

The device drive signal(s) for airflow generation or fan applications are different than for APPS applications. For example, in an air movement or fan application, device 890 may be operated by applying the same drive signal to both membranes 102a and 102b to create a pressure differential between the volume within chamber 105 and the surroundings outside device 890. , the two membranes (102a and 102b) may be actuated to move synchronously. In contrast, in an APPS application, the device 890 can interleave (such as S102a/S102b) or reverse polarity (S102a'', The two membranes (102a and 102b) are actuated to move synchronously in opposite directions (along the Z-axis) by applying drive signals to the membranes 102a and 102b (such as -S102a'').

The key difference between these two modes of operation is the different relationship between the chamber dimensions of the device and the operating frequency. As described in connection with the apparatus 890/830/850 for APPS applications, the operating frequency may be selected to generate a mode n standing wave within the chamber. In other words, the operating frequency f _CY is related to the chamber width W ₁₀₅ by the formula W ₁₀₅ = n/2·λ _CY , where λ _CY = C/f _CY is the characteristic length or wavelength of f _CY . , n are small positive integers such as 1 to 3. On the other hand, for air movement or fan applications of devices 890/830/850, the conversion rate of membrane movement to air flow generally increases as the ratio λ _CY /W _chamber increases, where W _chamber is the width of the chamber 105 of the air pulse generator 890/830/850, which corresponds to W ₁₀₅ ; In other words, the conversion rate of membrane movement to airflow typically depends on the chamber of the airflow generator for air movement or fan applications (corresponding to chamber 105 of the air pulse generator 890/830/850). As the pressure within chamber 105 becomes more uniform, it increases, which is in direct contrast to the desire to maximize the pressure gradient (or pressure non-uniformity within chamber 105) of air pulse generator 890/830/850.

For example, in the air pulse generator 890, the resonant frequency f of the cantilever beam can be related to its length L by f∝1/L ³ so that W ₁₀₅ =λ _CY =3.6 mm at an operating frequency of 96 KHz. be. On the other hand, the operating frequency of the air pulse generator for air moving or fan applications is lowered from 96 KHz to 24 KHz, and the membrane part(s) and valve part(s) of the air pulse generator for air moving or fan applications are lowered from 96 KHz to 24 KHz. By lowering both resonant frequencies to 24 KHz as well, the width of the membrane section can be increased from 0.94 mm to 1.44 mm, and the width of the valve section can be increased from 0.46 mm to 0.73 mm, resulting in The resulting chamber width can be 2 x (0.1 + 0.73 + 0.2) + 1.44 = 3.5 mm, which is much shorter than the wavelength of 14.6 mm at a frequency of 24 KHz, and the air flow of the membrane movement shows a high conversion rate to Thus, despite nearly identical cross-sectional views, the air pulse generator and air for air movement or fan applications have a resonant frequency of 24 KHz for both membrane section(s) and valve section(s). Driving both of the air pulse generators for moving or fan applications with the same waveform at 24 KHz may be suitable for air moving applications, although membrane sections 102a and 102b may be driven with interleaved waveforms S102a', S102b' or symmetrical An air pulse generator 890 driven by waveforms S102a", -S102a" and producing approximately zero net air movement over each operating cycle T _CY may be optimized for sound production applications and is suitable as an air movement device. There is a possibility that there is no.

In summary, while symmetrical membrane displacement of membrane portions 102a/102b or 102c/102d of device 890 can be used to maximize intrachamber pressure gradients for APPS applications (membrane portions with signals of the same polarity Synchronous/identical membrane displacements (by driving the airflow) can be employed to maximize the conversion rate of membrane movement to airflow. In another aspect, for APPS applications, the chamber width (in the X direction) W ₁₀₅ is n/2× may be equal to or close to λ _CY (where n is a small positive integer); whereas for air movement applications, the chamber width (in the X direction) of an air pulse generator for air movement or fan applications ) may be much smaller than λ _CY /2 to maximize the conversion rate of membrane movement to air flow.

Different structural embodiments (air pulse generation) devices are described in the following paragraphs. For example, FIG. 8 is a schematic diagram of a cross-sectional view of an air pulse generator 880 according to one embodiment of the present application. The membrane structure 12 of the air pulse generator 880 includes one membrane section, which is divided into membrane subparts 102e', 102f', and 102g. Membrane sub-parts 102e' and 102g can be distinguished according to slits 113e and 113f on the membrane parts. The membrane structure 12 of the air pulse generator 880 with membrane sub-sections 102e' and 102g may/function as membrane sections 102a and 102b of the air pulse generator 890 (or membrane sections 102c and 102d of the air pulse generator 830). It is possible.

In APPS applications, membrane subsections 102e' and 102g may be driven by a membrane drive signal pair similar to membrane drive signal pair (S102a, S102b)/(S102a', S102b')/(S102a, S102b'). , so that membrane sub-sections 102e' and 102g may move substantially in opposite directions to have symmetrical membrane displacements. Similar to downwardly curved membrane portion 102a and upwardly curved membrane portion 102b, membrane sub-sections 102e' and 102f' may be concavely curved to curve downwardly, and membrane sub-sections 102f' and 102g to curve upwardly. It can be convexly curved and vice versa.

FIG. 9 is a schematic diagram of a cross-sectional view of an air pulse generator 800 according to one embodiment of the present application. Membrane structure 12 of air pulse generator 800 includes membrane portions 102g and 102h, which are fixed on support 110 at the center of air pulse generator 800. The slits/tips of membrane portions 102g and 102h are located proximate sidewalls 804L and 804R.

Valves 101 and 103 of air pulse generators 890/830/850/880 are not present in air pulse generator 800. When membrane portions 102g and 102h are driven by the pair of membrane drive signals (S102a, S102b)/(S102a', S102b')/(S102a'', S102b''), membrane portions 102g and 102h are driven by an air pulse generator. Valve 101 of air pulse generator 890 by utilizing the slit between membrane portions 102g, 102h and wall 111 to perform the AM ultrasonic carrier rectification function of openings 112, 114 of valves 101, 103 of 890. , 103 and the pressure generating function of the membrane portions 102a, 102b of the air pulse generator 890.

As a result, the membrane portion 102g may vibrate to form an aperture 112g that functions as the aperture 112 of the valve 101, while producing a maximum/minimum change in pressure (e.g., a first peak pressure pk ₁ ). It is possible. The membrane portion 102h can vibrate to form an opening 114h that functions as the opening 114 of the valve 103, while producing a maximum/minimum change in pressure (e.g., a second peak pressure pk ₂ ). obtain.

The air pressure waveform P707L can be expressed as P707L∝(S _IN ·sin(ωt)+Z _0AC ) ² when Z102a>Z _O/C , and as P707L=0 otherwise. When Z102b>Z _O/C , the air pressure waveform P707R∝(S _IN ·sin(ωt)+Z _0AC ) ² can be expressed, otherwise, P707R=0. Here, waveforms Z102a and Z102b represent displacements of membrane portions 102g and 102h, respectively; waveforms P707L and P707R represent air pressure (outside chamber 105) at ports 707L and 707R, respectively.

A negative bias voltage is applied to the bottom electrode(s) of the actuator(s) of membrane portion 102g/102h, so that when the input AC voltage is 0V, the (tip) of membrane portion 102g/102h in the Z direction ) position is raised to equal or slightly exceed the displacement level Z _O/C . In other words, Z _0AC can be positive. If the position (of the tip) of the membrane portion 102g/102h in the Z direction is less than the displacement level _ZO/C when the input AC voltage is 0V, _Z0AC can be negative and the low level input signal(s) ), clipping phenomena similar to class B amplifiers may occur. Due to the clipping phenomenon, the membrane portions 102g/102h may not open completely.

If Z _0AC is a positive number, the aggregated on-axis output sound pressure of air pulse generator 800 (i.e., P800=P707R+P707L) can be expressed as:
P800∝(S _IN・sin(ω・t)+Z _0AC ) ² +(S _IN・sin(−ω・t)+Z _0AC ) ² =S _IN ²・(1−cos ² (2ω・t))+2・When Z _0AC ² , |S _IN・sin(ω・t)|<Z _0AC (formula 5a),
P800∝(S _IN・sin(ω・t)+Z _0AC ) ² ≒1/2sin ²・(1−cos ² (2ω・t))+2・S _IN・sin(ω・t)・Z _0AC , |S _IN・sin(ω・t)｜≫Z In the case of _0AC (Equation 5b), and P800∝(S _IN・sin(ω・t)) ² ≒1/2sin ²・(1−cos ² (2ω・t) ), when Z _0AC →0+ (Equation 5c).
Z _0AC is the amount of displacement of the membrane with respect to the displacement level Z _O/C when the input AC voltage is 0V.

In embodiments, Z _0AC has a small positive value to reduce the second term 2·Z _0AC ² of Equation 5a and the inaudible second term 2·S _IN ·sin(ω·t)·Z _0AC of Equation 5b. can be set to the value of . For example, Z _0AC can range between 1% and 10% of the maximum membrane displacement.

In one embodiment, linearity compensation may be performed by a DSP functional block embedded within the host processor to compensate for the nonlinearity of S _IN ² in Equations 5a-5c.

By setting Z _0AC to a small positive value, membrane portions 102g/102h may open slightly when the input AC voltage is 0V. Considering the symmetry of the membrane drive signals (S102a, S102b)/(S102a', S102b')/(S102a", S102b"), at least one of the apertures 112g, 114h may be slightly open at any time/ can be formed. Therefore, the pressure changes in the chamber 105 due to the rectifying effect of the openings 112g, 114h can be balanced and the vent opening(s) 713T or wider slit openings (113a*/113b*) present in the air pulse generator 800. do not.

In air pulse generator 800, the effects of full-wave rectification and synchronous demodulation can be produced by air pulse generator 800 regardless of whether resonance occurs within chamber 105. Even without standing waves to generate maximum sound pressure at or near sidewalls 804L and 804R, such maximum sound pressure is simply due to the physical location of openings 112g, 114h in membrane portions 102g, 102h. , and symmetrical membrane drive signals (S102a, S102b)/(S102a', S102b')/(S102a'') that drive the actuators of membrane portions 102g, 102h to produce maximum displacements near sidewalls 804L and 804R. , S102b''). For example, membrane portion 102g may be actuated to compress a first portion/volume 105a (top of membrane portion 102g) within chamber 105 to maximize local pressure. Membrane portion 102h may be actuated to expand a second portion/volume 105b (top of membrane portion 102h) within chamber 105 to minimize local pressure. The pressure profile over time within parts/volumes 105a and 105b may be identical to that of a standing wave at first mode resonance. In other words, the air pulse generator 800 can achieve full wave rectification and synchronous demodulation without chamber 105 resonance, thereby increasing flexibility in the design of the air pulse generator.

If a resonance occurs in the air pulse generator 800, the output of the air pulse generator 800 can benefit from the standing wave of such resonance. For example, if the width W ₁₀₅ of the chamber 105 of the air pulse generator 800 is equal to half the wavelength (λ/2) corresponding to the operating frequency f _CY , a pressure profile similar to that of a standing wave will be generated in the membrane portion 102g and 102h, thus increasing the power caused by the standing waves already established in the chamber 105.

Enclosure-less

The air pulse generator 890/850/830 generates a pair of out-of-phase baseband radiations such as those produced by a conventional loudspeaker (i.e., forward radiation and phase-inverted backward radiation). Since the air pulse generator 890/850/830 does not produce any (which is to avoid canceling the radiation) is also not required. Therefore, the air pulse generator 890/850/830 that generates sound can be enclosure-less.

In the case of device 890, by utilizing the first mode resonance of chamber 105 and the interleaved timing of valve opening, air pulse generator 890 generates two emissions that are in phase instead of 180° out of phase. generate. Proper timing alignment between the opening timing of the valves 101/103 (indicated as Z101/Z103 in Figure 2) and the pressure waves P112/P114 ensures that the acoustic energy is properly phased and the ultrasound radiation is It is converted to double the baseband output SPL, increasing total acoustic energy utilization and eliminating the need for an enclosure while achieving effective demodulation of ultrasound AM signals.

acoustic filter

An acoustic filter may be added before the air pulse generator. For example, FIG. 10 is a schematic diagram of an air pulse generator 890 disposed in configuration A00 according to one embodiment of the present application. FIG. 11 is a schematic diagram of an air pulse generator 890 disposed within arrangement A30 according to one embodiment of the present application. The acoustic air pressure measured at ports 707L and 707R of air pulse generator 890 includes not only the demodulated AM ultrasound waves P707L and P707R, but also the ultrasound waves generated by the movement of valves 101 and 103. obtain. The symmetrical movement of valves 101 and 103 can be characterized as dipole. The superposition of ultrasonic waves generated by the movement of valves 101 and 103 peaks along the planes of valves 101 and 103 and zeros on the central plane between side walls 804L and 804R. Configuration A00/A30 may be configured to minimize ultrasound generated by movement of valves 101 and 103, and thus may function as an acoustic filter.

In FIG. 10, configuration A00 may include a funnel structure A05 configured to filter out ultrasound generated by movement of valves 101/103. Funnel structure A05 may have a wide opening inside configuration A00, sloped sides, and a narrow tube near the outside of configuration A00. The wide opening of the funnel structure A05 may be smaller than the width W ₁₀₅ of the chamber 105. Funnel structure A05 combines the outputs from ports 707L and 707R, causing the ultrasonic waves produced by the symmetrical movement of valves 101 and 103 to cancel each other out, leaving wave P890, which is the sum of waves P770L and P770R/ It is superimposed.

In FIG. 11, configuration A30 may include port A07 and external chamber A06, which serve as output ports for configuration A30. The width Wa06 between the side walls A06T, A06B of the external chamber A06 may be equal to the width W105 of the chamber ₁₀₅ (e.g. half of λ _CY ), so that the standing wave has a frequency f _CY (of the first mode resonance ) and frequency 2·f _CY (in the case of second-order mode resonance). The width Wa07 of the port A07 may be smaller than the width _W105 of the chamber 105. The width Wa07 of the port A07 may be equal to half the width W ₁₀₅ of the chamber 105 or one quarter of λ _CY .

Configuration A30 is configured to filter out ultrasound generated by movement of valves 101/103. For ultrasound generated by symmetrical movement of valves 101 and 103 with frequency f _CY , the acoustic energy is transferred to an external chamber with a pneumatic node at/near the midpoint between side walls A06T and A06B. There may be a first mode resonance of A06, and the standing wave pressure may be coupled to zero across the width Wa07 of port A07. For a sound wave P890 with a pulse rate of 2·f _CY , the acoustic energy is distributed at the midpoint between side walls A06T and A06B, which is also the center of port A07/secondary of external chamber A06 with an antinode of air pressure near the midpoint. mode, and maximum output pressure may occur when the pressure of the standing wave is integrated over the width Wa07 of port A07. By utilizing two different resonance modes, the external chamber A06 removes the ultrasound spectral component at frequency f _CY by first mode resonance and removes the ultrasound spectral component at frequency 2 f _CY by second mode resonance (i.e. , wave P890).

In FIG. 11, configuration A30 may include film A08, which may be made of a hydrophobic material. Film A08 filters out the remaining ultrasound spectral components at frequency 2 f _CY by means of protection (to prevent the ingress of dust, vapor and moisture) and acoustic resistance (by forming a low-pass filter with the volume of external chamber A06). for damping).

FIG. 12 is a schematic diagram of a mobile device A60 according to one embodiment of the present application. Two air pulse generators A02 and A03, each of which may be any of the air pulse generators 890/850/830, are mounted on the edge A01 of a mobile device A60, such as a smartphone or a notepad. Ports 707L and 707R of air pulse generators A02, A04 may face outward, and ultrasound generated by air pulse generators A02, A03 may pass through orifice array A04, A05. Mobile device A60 utilizes the structure of configuration A00 or A30 to remove the ultrasound spectral component at frequency f _CY generated by the movement of valves 101 and 103, while passing wave P890 of frequency 2·f _CY . The film A08 of the configuration A30 that allows to further reduce the remaining ultrasound spectral components around the frequency 2·f _CY .

FIG. 13 is a schematic diagram of a cross-sectional view of an air pulse generator 300 according to one embodiment of the present application. Similar to the air pulse generator 890, when a standing wave is formed by the chamber 105 of the air pulse generator 300, the motion of the membrane portions 102c, 102d of the air pulse generator 300 is symmetrical and has an approximately zero net of air movement. Due to the approximately zero net air movement over each operating cycle T _CY , the majority of the energy provided by the membrane portions 102c/102d will be acoustic energy (in the form of pneumatic gradients or standing waves), and the approximately zero energy will be , kinetic energy (air mass transfer, i.e. wind).

FIG. 14 is a schematic illustration of a cross-sectional view of an air movement device 100 for moving an air volume from one port of the device to another port, according to one embodiment of the present application.

In contrast to air pulse generators 850/890, the vibrational frequency of membrane 102 of air flow generator 100 produces a wavelength λ much larger than the width of chamber 105, and the pressure within chamber 105 is assumed to be uniform. It is conceivable. Interleaved valve actuation signals S101/S103 open valve portions 101/103 in a time-interleaved manner or 180° out of phase, allowing air to flow either from port 107 to port 108 or from port 108 to port 107. It may be configured to cause movement. For example, if valves 101/103 are opened and valves 103/101 are closed when membrane 102 moves in the positive Z direction (+Z direction) to compress the volume within chamber 105, air will flow through port 107. /108 from chamber 105. Conversely, if valves 101/103 are opened and valves 103/101 are closed when membrane 102 moves in the negative Z direction (-Z direction) to expand the volume of chamber 105, air will flow through port 107. /108 into chamber 105.

The cap 104 of the air moving device 100 functions as a heat sink/pad and protects heat generating components such as, but not limited to, a notebook central processing unit (CPU) or a smartphone application processor(s) (AP). come into physical contact with. Cap 104 may be made of a thermally conductive material such as aluminum or copper. Fine fins (not shown) may be formed on the surface of the cap 104 within the chamber 105 to improve heat transfer efficiency, but are not limited thereto.

In particular, in the air pulse generator 850/890, the cap 104 of the air device 100/300 is replaced by a top plate 804T and spacers 804L, 804R, which also function as side walls. Top plate 804T may be a printed circuit board (PCB) or land grid array (LGA) substrate and includes metal traces, vias, and contact pads that may be otherwise disposed on substrate 109 or plate 115. The thickness is 0.2 to 0.3 mm for the top plate 804T, 0.05 to 0.15 mm for the side walls 804L/804R, and 0.25 to 0.35 mm for the wall 111. The total thickness of the air pulse generator can be, but is not limited to, 0.6-0.8 mm.

Additionally, the pulse interleaving concept disclosed in US Pat. No. 10,536,770 can also be applied to the present application. In other words, in order to improve the sound quality while generating ultrasonic acoustic pulses for APPS, in one embodiment, multiple air pulse generators (e.g., multiple air pulse generators 100) are connected to one Can be cascaded together to form a single air pulse generator. The drive signals for air pulse generator 100 (e.g., membrane drive signals S102a/S102b/S102 or valve drive signals S101/S103) may be interleaved to form interleaved groups, and may be separated from the human hearing range. However, as a result, the effective air pulse rate can be increased to twice as high a frequency. For example, pulses of the membrane drive signal of one air pulse generator 100 may be interleaved with pulses of the membrane drive signal of another air pulse generator 100 such that the aggregate air pulse of one air pulse generator 100 is , may be interleaved with aggregate air pulses of another air pulse generator 100 to increase the effective air pulse rate. Alternatively, each pulse of the membrane drive signal of one air pulse generator 100 is located at/near the midpoint between two consecutive pulses of the membrane drive signal of the other air pulse generator 100; As a result, each aggregate air pulse of one air pulse generator 100 is located at/near the midpoint of two consecutive aggregate air pulses of the other air pulse generator 100, so as to increase the effective air pulse rate. obtain. In one embodiment, two air pulse generators 100, each designed to operate at an operating frequency T _CY of 24 KHz, are arranged side by side or mounted back-to-back and in an interleaved manner. , resulting in an effective air pulse rate of 48 KHz.

Illustratively, FIG. 15 is a schematic diagram of an air pulse generator 400 according to one embodiment of the present application. The air pulse generator 400 can be thought of as two air pulse generators 100 and 100' stacked back to back. In the air pulse generator 400, the two chambers 105 and 105' of the two air pulse generators 100 and 100' are connected to each other via an opening 116 to form a chamber 106 of the air pulse generator 400. .

The air pulse generator 400 may have a first valve section 101, a second valve section 103, a third valve section 101', and a fourth valve section 103'. The first anchor by which the valve part 101 is fixed to the wall 111 and the second anchor by which the valve part 103 is fixed to the wall 111 are aligned in the X direction; while the first anchor and the valve part 101' is aligned in the Z direction with the third anchor fixed to the wall 111. Valve sections 101 and 103 (or valve sections 101' and 103') are symmetrical with respect to the YZ plane; while valve drive signal S101 (or S103) applied to valve sections 101 and 101' drops to zero. The (non-actuated) valve parts 101 and 101' (or valve parts 103 and 103') are then symmetrical about a second plane (eg, the XY plane) that is not parallel to the YZ plane. Valve parts 101 and 101' (or valve parts 103 and 103') are non-coplanar, while (non-actuated) valve parts 101 and 103 (or valve parts 101' and 103') are
When the valve actuation signals S101 and S103 applied to valve portions 101 and 103 drop to zero, they may be coplanar.

In one embodiment for an APPS application, by interleaving the drive signals of the two air pulse generators 100, the displacement profile(s) of the membrane portion 102 (or valve portions 101, 103) of the air pulse generator 400 is It may be mirror symmetric with the displacement profile(s) of the membrane section 102' (or valve sections 101', 103') of the air pulse generator 400. Alternatively, by interleaving or inverting the drive signals of the two air pulse generators 100, the displacement profile(s) of the membrane portion 102 (or valve portions 101, 103) of the air pulse generator 400 is The displacement profile(s) of membrane section 102' and (or valve sections 101', 103') of pulse generator 400 may be the same, such that (the direction and magnitude of) the displacement of membrane section 102 is: is equal to (the direction and magnitude of) the displacement of membrane portion 102', thereby canceling out pressure fluctuations within chamber 106. Membrane portion 102 may be parallel to (or offset to align with) membrane portion 102'.

In one embodiment for air movement applications, the characteristic length λ _CY is generally much longer than the dimensions of the air pulse generator 400. Since the displacement of membrane portion 102 may be equal to the displacement of membrane portion 102', air pulse generator 400 may include only one membrane portion and one of membrane portions 102, 102' may be removed, thereby , reduce power consumption and improve operating efficiency.

power saving

In another aspect, the output of the air pulse generator is related to A(t) p(t), where A(t) is the area of the aperture 112/114 and p(t) is the area of the chamber 105 represents the air pressure. In other words, the opening 112/114 of the valve 101/103 is directly related/proportional to the intensity of the output of the air pulse generator. Specifically, the maximum SPL output is determined by the maximum value of the air pressure p(t) in the chamber 105 generated by the membrane movement and the maximum value of the area A(t) of the openings 112/114 generated by the valve movement. It is a combination of By appropriately modulating/manipulating the area A(t), the operating power of the air pulse generator can be reduced.

The area A(t) may not change at a rate audible to human hearing, but the valve drive voltage S101/S103 may be slowly adjusted depending on the volume or envelope of the sound being generated. It can be adjusted by changing. For example, the valve drive voltage S101/S103 may be controlled by envelope sensing with an attack time of 50 milliseconds and a release time of 5 seconds. When the sound produced by the air pulse generator is consistently low volume, the valve drive voltage S101/S103 may be gradually reduced with a 5 second (long) release time. When generating high sound pressure, the valve drive voltage S101/S103 can be increased with a (short) 50 ms attack time.

In summary, the air pulse generator of the present invention first vibrates its membrane structure and then increases the sound pressure (or air movement) in response to the maximum/minimum occurrence of sound pressure (or air velocity). Sound pressure (or air movement) may be generated by opening/closing its valve structure for filtering/reshaping and finally outputting sound waves (or air flow) under full wave rectification effect. Synchronous demodulation is performed by opening/closing the valve structure in a phase-locked and time-aligned manner and/or by opening/closing the valve structure in response to the occurrence of a sound pressure maximum/minimum (or air velocity) and/or the valve portion of the valve structure. may be performed by opening/closing in a temporally interleaved manner.

Those skilled in the art will readily appreciate that many modifications and variations of the apparatus and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the scope of the claims appended hereto.

Claims (28)

An air pulse generator comprising:
membrane structure and valve structure;
a cover structure, wherein a chamber is formed between the membrane structure, the valve structure, and the cover structure;
an air wave oscillating at an operating frequency is formed within the chamber;
the valve structure is configured to operate to perform an opening and closing operation to form at least one opening, the at least one opening connecting air within the chamber with air outside the chamber;
the opening/closing operation is synchronized with the operating frequency;
Air pulse generator. the air pulse generator generates an acoustic sound according to an input audio signal;
the air wave within the chamber generated by the membrane structure includes an amplitude modulated waveform corresponding to a carrier wave component having the operating frequency and a modulated component corresponding to the input audio signal;
An air pulse generator according to claim 1. The membrane structure is configured to be actuated to generate the air wave in accordance with a membrane drive signal, the membrane drive signal including a pulse amplitude modulation signal, the pulse amplitude modulation signal being generated in accordance with an input audio signal. Ru,
An air pulse generator according to claim 1. the membrane structure has a first membrane portion and a second membrane portion;
the first membrane portion and the second membrane portion are configured to be actuated simultaneously according to a first membrane drive signal and a second membrane drive signal to generate an air wave;
An air pulse generator according to claim 1. the first membrane drive signal includes a first pulse amplitude modulated signal, the first pulse amplitude modulated signal includes a plurality of first pulses distributed in time according to the operating frequency;
the second membrane drive signal includes a second pulse amplitude modulated signal, the second pulse amplitude modulated signal includes a plurality of second pulses distributed in time according to the operating frequency;
The air pulse generator according to claim 4. The rising edge of the first pulse temporally coincides with the falling edge of the second pulse.
The air pulse generator according to claim 5. the first pulse and the second pulse are temporally interleaved;
The air pulse generator according to claim 5. the sum of the first membrane drive signal and the second membrane drive signal is constant;
The air pulse generator according to claim 4. the membrane structure generates a pressure gradient having a pressure gradient direction within the chamber during the interval;
the interval is within half an operating cycle;
the operating cycle is the reciprocal of the operating frequency;
An air pulse generator according to claim 1. the pressure gradient direction of the pressure gradient generated by the membrane structure is substantially parallel to the membrane structure;
An air pulse generator according to claim 1. the membrane structure has a first membrane portion and a second membrane portion;
During an interval within the first half of the operating cycle , the first membrane section is actuated to compress a first section of the chamber, and the second membrane section is actuated to compress a second section of the chamber. actuated to expand the sections so that a pressure gradient is created in the direction of the pressure gradient from the first section to the second section;
An air pulse generator according to claim 1. the membrane structure generates a first air pressure gradient at a location within the chamber during a first interval within the first half of an operating cycle;
the membrane structure generates a second air pressure gradient at the location within the chamber during a second interval within the second half of the operating cycle;
the first pneumatic pressure gradient and the second pneumatic pressure gradient have opposite directions;
the operating cycle is the reciprocal of the operating frequency;
An air pulse generator according to claim 1. a first magnitude of the first pneumatic gradient and a second magnitude of the second pneumatic gradient are substantially the same;
The air pulse generator according to claim 12. the membrane structure has a membrane portion configured to be actuated to produce membrane movement having a direction of membrane movement;
a pressure gradient having a pressure gradient direction is generated due to the membrane movement;
the membrane movement direction and the pressure gradient direction are substantially perpendicular to each other;
An air pulse generator according to claim 1. A sound generation method applied in an air pulse generator, the method comprising:
forming an air wave within a chamber, the air wave oscillating at an operating frequency, and the chamber being formed within the air pulse generator;
forming at least one aperture in the air pulse generator at an open frequency, the at least one aperture connecting air within the chamber with air outside the chamber;
the open frequency is synchronized with the operating frequency;
Sound generation method. The step of forming the air wave at the operating frequency includes:
forming an amplitude modulated waveform according to an input audio signal;
The amplitude modulation waveform includes a carrier component having the operating frequency and a modulation component corresponding to the input audio signal.
The sound generation method according to claim 15. The air pulse generator has a membrane structure, and the step of forming the air wave at the operating frequency includes:
driving the membrane structure with a membrane drive signal to generate the air wave;
the membrane drive signal includes a pulse amplitude modulated signal generated in accordance with an input audio signal;
The sound generation method according to claim 15. The air pulse generator has a membrane structure, the membrane structure has a first membrane portion and a second membrane portion, and the step of forming the air wave at the operating frequency includes:
driving the first membrane portion with a first membrane drive signal;
driving the second membrane portion with a second membrane drive signal;
the air wave is generated by simultaneously driving the first membrane portion with the first membrane drive signal and driving the second membrane portion with the second membrane drive signal;
The sound generation method according to claim 15. generating the first membrane drive signal in accordance with an input audio signal, the first membrane drive signal including a first pulse amplitude modulation signal, the first pulse amplitude modulation signal having the operating frequency comprising a plurality of first pulses distributed in time according to;
generating the second membrane drive signal in accordance with the input audio signal, the second membrane drive signal including a second pulse amplitude modulation signal, the second pulse amplitude modulation signal being responsive to the operation; further comprising: a plurality of second pulses distributed in time according to frequency;
The sound generation method according to claim 18. the step of generating the first pulse amplitude modulation signal and the step of generating the second pulse amplitude modulation signal, the rising edge of the first pulse being temporally aligned with the falling edge of the second pulse. matches,
The sound generation method according to claim 19. generating the first pulse amplitude modulated signal and generating the second pulse amplitude modulated signal, the first pulse and the second pulse being interleaved in time;
The sound generation method according to claim 19. generating the first pulse amplitude modulation signal and generating the second pulse amplitude modulation signal, wherein the sum of the first membrane drive signal and the second membrane drive signal is constant. ,
The sound generation method according to claim 19. The air pulse generator has a membrane structure, and the step of forming the air wave at the operating frequency includes:
generating a pressure gradient in the chamber, through the membrane structure, having a pressure gradient direction;
the pressure gradient direction of the pressure gradient generated by the membrane structure is substantially parallel to the membrane structure;
The sound generation method according to claim 15. The step of generating the pressure gradient having the pressure gradient direction within the chamber includes:
generating the pressure gradient having the pressure gradient direction in the chamber during an interval;
the interval is within half an operating cycle;
the operating cycle is the reciprocal of the operating frequency;
The sound generation method according to claim 23. The membrane structure has a first membrane portion and a second membrane portion, and the step of generating the pressure gradient having the pressure gradient direction:
compressing a first portion of the chamber by actuating the first membrane portion during an interval within a first half of an operating cycle ;
expanding a second portion of the chamber by actuating the second membrane portion during the interval;
the pressure gradient direction is from the first portion to the second portion;
The sound generation method according to claim 23. The air pulse generating device has a membrane structure and the step of forming the air wave at the operating frequency includes:
the membrane structure generating a first air pressure gradient at a location within the chamber during a first interval within the first half of an operating cycle;
the membrane structure generating a second air pressure gradient at the location within the chamber during a second interval within the second half of the operating cycle;
the first pneumatic gradient and the second pneumatic gradient have opposite directions;
the operating cycle is the reciprocal of the operating frequency;
The sound generation method according to claim 15. generating the first pneumatic gradient having a first magnitude and the second pneumatic gradient having a second magnitude;
the first magnitude of the first pneumatic gradient and the second magnitude of the second pneumatic gradient are substantially the same;
The sound generation method according to claim 26. The membrane structure includes a membrane portion, and the step of forming the air wave at the operating frequency includes:
actuating the membrane portion to produce membrane movement having a direction of membrane movement such that a pressure gradient is formed;
the pressure gradient having a pressure gradient direction is generated due to the membrane movement;
the membrane movement direction and the pressure gradient direction are substantially perpendicular to each other;
The sound generation method according to claim 15.