JPH07107588A - Method for constructing sound source - Google Patents

Abstract

PURPOSE:To provide a required acoustic signal without sending the acoustic signal to the unrequired space and without the physical restriction by emitting the soundwave corresponding to the audible modulation signal by taking the space corresponding to the focusing position of the rotating ellipsoid as a sound source. CONSTITUTION:An originating ultrasonic transducer 3 is installed on the inside focus 2 of a part 1 of a rotating body. The ultrasonic output of the transducer 3 is emitted towards the part 1 of the rotating ellipsoid. Then, it is converted into another focus 8 and it is further converged and diverged. In passing the route, the ultrasonic wave takes the audible signal whose amplitude is modulated as the isolate sound source gradually and it is separated and generated. Thus, the audible soundwave is included in the direction shown by the doted lines. Thus, when a listner 9 is in the divergence area after the convergence, he hears the soundwave as the sound source of the sound wave is in the focus 8. In this case, the audible sound wave is not beyond the doted line range and the listner 9 does not hear the sound source other than the focus 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of constructing a sound source of a characteristic audible range signal in a space other than a sound source.

[0002]

2. Description of the Related Art Conventionally, a method of driving a transducer such as a speaker is generally used as a method of generating an acoustic signal in an audible range. Therefore, the position where the sound is generated, that is, the sound source is the position of the diaphragm. In the stereo listening system, it sounds as if it is sounding at the middle position between the two speakers, but this is a sensory sound source position, and there is no sound source at that position. It is also possible to arrange the speakers on a spherical surface and focus the sound waves on the center of the spherical surface, but the actual array speakers not only send the sound waves toward the center of the sphere, but also radiate the sound waves in other directions. Therefore, a clear sound source effect with the center of the sphere as the sound source cannot be obtained. Also, regarding the beam-shaped sound wave forming method that sends sound waves only in a certain direction, some effects have been obtained by devising the speaker, the shielding plate, and the driving method of a special arrangement, but the adjustment and the driving device become large. Further, a method of arraying a large number of transducers on a plane has been attempted by using the same principle as that of the present invention in order to obtain a beam-shaped audible sound, but the efficiency is poor because only energy on the central axis of the transducer is used.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a technique for installing an actual sound source in a place where there is no physical sounding body, and is useful for improving human life in the following cases. (1) It is customary to listen to conventional sound waves at a distance from the sound source. For example, when listening to music, a pair of speakers are often installed in one corner of a room to emit considerable acoustic energy for viewing. Therefore, in the same room, sound waves may propagate in directions other than the listener, and the adjacent room, the outdoors, or even the adjacent house may be affected by the music.
To eliminate this, it is possible to use headphones, but this creates a new feeling of restraint and it is difficult to use for a long time. (2) The use of an OA device that generates a voice that only needs to be communicated to the user may be transmitted to a portion of the room where the sound information is not needed, resulting in noise. (3) When listening to TV, the fact that the received voice is diffused throughout the room for personal listening may only be taken by other people as scattering noise, and conversely for people with hearing loss. May personally want a higher level acoustic signal than others. (4) If you want to convey a message to attendees at a meeting, you often have a personal messenger. This is because there is no way to send a voice signal personally.

In the case of the above-mentioned required example, it is necessary to obtain the necessary acoustic signal without contaminating the unnecessary space with the acoustic signal and without being physically restricted. For this,
It is conceivable to install a sound source that does not exist as an object near the listener's ear to transmit a small volume level, or to send a beam-shaped sound wave to the listener's ear from a distance.
The present invention intends to realize either of these methods.

To explain the principle of the present invention, a nonlinear characteristic with respect to a sound wave of air is generated while an ultrasonic wave from an ultrasonic transducer for transmission driven by an electric signal in an ultrasonic range amplitude-modulated by an audible sound range signal propagates in the air. It applies the parametric array effect in which a sound wave corresponding to the audible range signal is generated by self-demodulation from. That is, in the case of claim 3 which is a specific example of claim 1, when the transducer is placed at one (first) focal point of the inner surface of the spheroid and the ultrasonic wave is generated from there, the spheroid is generated. All the waves reflected by the inner surface of the laser converge on another (second) focal point and then diverge again. During this path, the audible range modulated signal component of the modulated signal is demodulated by the parametric array effect, and the sound waves corresponding to this signal are similarly converged and diverged. Since this state is the same wavefront as the speaker whose sound source is the second focus, an audible sound is heard from the second focus by the listener in the propagation area space of this wavefront. In addition, this audible sound wave has a sharp directivity in the traveling direction of the original ultrasonic wave with the same effect as that in which the speakers in the audible range of tuning are arranged in an array in the traveling direction. The feature is that only the sound of the route is heard.

In the case of claim 4, which is a specific example of claim 2, the distance between the focal points in the case of claim 3 is extremely large, and the second focal point is infinite. Sound waves emitted from the and reflected on the inner surface become a plane wavefront and travel in the form of a beam. For this reason, the sound wave can reach a long distance with a small energy loss due to divergence, and can transmit an audible signal only within the range of the beam diameter. This method is efficient because all of the acoustic energy generated from the transducer can be used as the target sound source because it is collected by the reflecting surface. In particular, the audible sound generated by the parametric array has a high directivity in principle, so it is a relatively small reflection. All of them can be combined in a plane, and a higher efficiency can be obtained than the method of arranging transducers on a plane to form a beam.

[0007]

A sound source according to an example of a configuration method of the present invention is a sound source, and a drive circuit for generating a sinusoidal electric signal in an ultrasonic range which is amplitude-modulated by an electric signal corresponding to an audible sound wave including voice, and this signal. It consists of an ultrasonic transducer for transmission driven by and a part of a concave surface having an area including a part perpendicular to the line connecting the two focal points of the inner surface of the spheroid, A sound wave corresponding to an audible sound modulation signal is emitted using a space corresponding to a position as a sound source.

As an example of the extreme size of the spheroid, when the distance between the two focal points is much longer than the distance between the focal point and the inner surface of the ellipsoid, the second focal point becomes far and the reflector becomes It emits a beam-shaped audible sound wave having a plane wavefront of an area corresponding to the size.

The parametric array effect used as a principle here outputs a wave-shaped demodulation signal different from the original amplitude modulation signal. Under typical conditions, it is known that the output waveform is the second derivative of the square of the amplitude of the amplitude-modulated ultrasonic signal. Even in such a case, since the signal component corresponding to the modulation signal is included, it is possible to listen to the contents sufficiently when the signal is a voice, etc. It should be processed so that In the above case, the transducer does not necessarily have to be at the focal position, and may be arranged so as to have a wavefront equivalent to the sound wave generated from the focal point.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to FIG. FIG. 1 is a sectional view of an embodiment according to claim 3 of the present invention, in which a transmitting ultrasonic transducer 3 is installed at a focal point 2 inside a part 1 of a spheroid. The drive signal of this transducer is input to the output 7 of the modulator 6 that amplitude-modulates the output of the oscillator 4 that emits a sine wave in the ultrasonic band with the audible range signal 5. The ultrasonic output of the transducer is emitted toward the part 1 of the spheroid, and according to the law of the ellipse, this sound wave follows the path of the broken line and then converges toward another focal point 8 after reflection, and after further convergence. Diversify. While following this path, the ultrasonic wave gradually changes the amplitude-modulated signal in the audible range into independent sound waves, separates and generates them, and accompanies them.

Therefore, the sound wave in the audible range is also included in the direction of the broken line arrow. Therefore, if the listener 9 is present in the divergent area after convergence, the sound wave will be heard by this person as if the sound source were at the focal point 8. In this case, since the audible sound wave does not go out from the above-mentioned directivity outside the range of the broken line, the listener 9 is characterized by not hearing any sound source other than 8. Further, since the sound source can be installed near the listener, the volume may be sufficiently low, so that even if this sound wave is scattered to the rear of the listener, it does not become so much noise behind. If necessary, a wall surface having a large sound absorbing effect may be provided behind the listener.

Embodiment (1) The distance between both focal points is 0.6 m,
Distance between the focal point and the reflecting surface on the axis connecting both focal points 0.6m
A part of the spheroid determined by the center of the intersection of the axis and the ellipsoidal surface is formed with gypsum, and a piezoelectric ceramic transducer (murata) is formed at the focal point.
40SR) and installed a square wave of 1 KHz for 10
It was confirmed from the sound pressure distribution by the microphone (Acor 4017) that a square wave component of 1 KHz was generated from the second focus when an electric signal of 40 KHz with an effective value of 10 V that was 0% modulated was applied, and 10 cm from the focus. Position 6
A value of 5 dB (A) was obtained. I also confirmed it by ear.

FIG. 2 shows the case of claim 4 in which the distance between the focal points is infinite. This is equivalent to changing the reflection curved surface from a spheroid to a paraboloid of revolution. Amplitude-modulated ultrasonic waves similar to the above emitted from the transducer 12 from the position of the focal point 11 on the reflecting surface 10 are reflected as shown by the broken line,
The reflected sound at each part proceeds in parallel. In addition, the wavefront is a plane that is perpendicular to the traveling direction due to the parabolic principle. Therefore, the listener 13 can listen to the audible sound waves under the same condition regardless of the distance within a certain distance range when the listener 13 is in the traveling area of the sound waves.

Embodiment (2) Distance between focal point and center 0.
A parabolic surface determined by 3 m was formed from gypsum with a radius of 0.2 m, and an ultrasonic signal similar to that in Example (1) was generated from the focus, and a square of 1 KHz was formed on the axis connecting the center of the parabola and the focus. The beam-like distribution of wave components was confirmed. About 62 dB on the axis
(A) was obtained. I also confirmed it by ear.

[0015]

As described above, according to the present invention, a point in the air can be used as a sound source and a beam-like sound wave can be formed. Depending on the former method, the sound source can be installed in front of the listener's eyes, so that the acoustic information can be transmitted to the listener even at a low volume. The listener is not as restrained as headphones. The sound source of the latter method can send an acoustic signal in the direction of a listener at a distance. In this case, the acoustic signal becomes a beam and the acoustic signal cannot be heard outside the beam. Unlike the conventional planar arrangement of transducers, this method effectively uses the output signal of the parametric array, so that an audible sound can be efficiently obtained. A sound source having such characteristics has never existed before and has various uses as a personal airborne acoustic communication system.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention using a spheroidal reflecting surface.

FIG. 2 is a view showing the principle of the present invention using the inner surface of a paraboloid of revolution. 1 spheroidal reflecting surface 2 first focus 3 ultrasonic transducer 4 sinusoidal oscillator 5 audible signal 6 modulator 7 amplitude modulation signal 8 second focus 9 Listener 10 Rotating parabolic reflective surface 11 Focus 12 Transducer 13 Listener

Claims (5)

[Claims] 1. An ultrasonic signal amplitude-modulated by a signal in an audible region is emitted toward a curved surface installed so that a reflected wave can be converged by a combination of an emission form and a reflection form, and a re-occurrence space after convergence is emitted. 2. The sound source configuration method according to, wherein the convergence point functions as a sound source of audible sound corresponding to the signal in the audible region. 2. The audible sound corresponding to a beam-shaped signal in the audible region during convergence, wherein the convergence point is an infinite far distance point from the reflecting surface. Sound source configuration method. 3. The ultrasonic wave according to claim 1, wherein the ultrasonic wave is emitted from one (first) focal point of the inner surface of the spheroid, reflected by a part of the inner surface, and converged and passed to the other (second) focal point. 2. A sound source configuration method, wherein the second focus is a sound source of audible sound corresponding to a signal in the audible region. 4. The sound source constructing method according to claim 2, wherein the distance between both focal points is infinite. 5. The sound source construction method according to claim 1, wherein a function of absorbing the ultrasonic wave is added to the reflection curved surface.