JP2004349795A - Local space loudly speaking method and program thereof, local space loudspeaker, and recording medium recording the program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method small in scale for enabling the reproduction of a sound in a local space and the reproduction of a sound in a wide band which are not compatible by an existing technique. <P>SOLUTION: In this local space loudly speaking method, an inputted signal is divided into the arbitrary number of frequency bands, a signal in one of the bands is reproduced by a primary sound source, a signal having the same band as that reproduced by the primary sound source is used as an input signal, the delay and frequency characteristic of a secondary sound source are controlled on the basis of an output signal from a sensor arranged on the boundary of an arbitrary local space. Thus, a sound emitted to the outside of the boundary is muffled, frequency modulation is applied to a sine wave of an ultrasonic band by other frequency bands obtained by performing frequency band division, and an ultrasonic resonation element is excited by the ultrasonic signal subjected to frequency modulation to generate a signal of the other frequency band as a sound. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
FIELD OF THE INVENTION
The present invention relates to a local space loudspeaker method for generating an audible person in a local space, a local space loudspeaker, a local loudspeaker program, and a recording medium storing the program.
[0002]
[Prior art]
When sound is radiated using a loudspeaker, it is possible to hear the sound from almost all directions with respect to the speaker, although the directional characteristics of the speaker used for reproduction are affected. Therefore, when a sound is reproduced only in a certain specific space and the sound is not leaked outside, that is, a local reproduction method is to be constructed, it is necessary to devise a loudspeaker or other loudspeaker or a reproduction method. is there. For example, it is conceivable to use a directional speaker system that emits sound only in a desired direction in order to realize the local space reproduction. As the speaker system, a method of realizing directivity by a geometrical shape of a horn or a reflector, such as using a horn speaker, or installing a speaker unit at a focal point of a reflector, or a plurality of speakers, A method of forming directivity by arranging loudspeakers in an array (for example, Non-Patent Literature 1). Using an ultrasonic speaker, a sound wave obtained by amplitude-modulating a carrier having strong directivity with a signal in an audible band. There is a method of emitting sound in the audible band by emitting the sound and performing self-demodulation (Patent Document 1).
[0003]
Among them, the method of realizing directivity by a geometric shape requires the use of a horn having a large diameter or a large reflector area in order to obtain sharp directivity particularly at low frequencies. It becomes a large-scale system. In addition, the method in which the speakers are arranged in an array can provide a certain degree of directivity even though it is smaller than a system using a horn or the like. However, its directivity is still not good enough.
On the other hand, in the method using the ultrasonic speaker, directivity according to the ultrasonic wave serving as a carrier wave is obtained, and it is possible to realize narrow-band directivity. However, due to the limitation of the modulation / demodulation mechanism, a sufficient reproduction sound pressure cannot be obtained in a low frequency range.
[0004]
Regardless of which method is used, in order to reproduce sound only in a local space, it is necessary to attach a loudspeaker such as a speaker to a ceiling or the like (Non-patent Document 1). It is necessary to build appropriate facilities.
On the other hand, as a means for realizing local space reproduction by a reproduction method, there is a sound field control method using the property of the Kirchhoff-Helmholtz integral equation (Non-Patent Document 2). This means that by controlling the sound pressure and sound pressure gradient (particle velocity) on the boundary surface of a given closed space, the original sound field in a closed space of the same shape in another location can be faithfully reproduced. Method. However, this method tends to be a large-scale system in theory, since it is necessary to densely arrange many sensors for observing sound pressure and sound pressure gradient (particle velocity) on the boundary surface. Have difficulty. Further, this method can be applied theoretically over all frequency bands, but when an actual system is operated, the controllable band is limited depending on the interval between sensors to be arranged.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-236730 [Non-Patent Document 1]
Two-dimensional array directional speaker, Journal of the Acoustical Society of Japan, Vol. 50, no. 11, PP. 948-950
[Non-patent document 2]
Ise, Journal of the Acoustical Society of Japan, Vol. 53, no. 9, PP. 706-713, 1997
[0006]
[Problems to be solved by the invention]
In order to realize sound reproduction only in a local space, it is reasonable to use a directional speaker or perform sound field control using the properties of the Kirchhoff-Helmholtz integral equation. It can be considered as However, in each case, there are the following problems.
First, a system using a directional speaker has the following problems. First, it is difficult at present to reproduce a sound in a wide frequency band, particularly a sound in a low frequency range, with sufficient directivity. Secondly, when such a directional speaker is used, if a sound is to be reproduced locally, it is necessary to install a speaker on the ceiling of the space. If such a large-scale device is not used, it is possible to prevent sound from leaking to the side of the directivity of the speaker, but it is impossible to control the sound reaching distance. That is, it is impossible to locally reproduce the sound by reproducing the sound only in a specific space and not leaking the sound to the surrounding space.
[0007]
On the other hand, in the sound field control method using the property of the Kirchhoff-Helmholtz integral equation, it is also possible to control sound reproduction including the arrival distance of the sound. However, in order to adapt it strictly over a wide frequency band, it is necessary to install a large number of sensors for observing sound pressure and sound pressure gradient (particle velocity). The number of sound sources also increases, making it difficult to realize. In addition, when operated as an actual system, the upper limit of the controllable frequency band is limited, and it is practically difficult to reproduce a wideband sound. That is, with the existing technology, it is not possible to achieve both the loudspeaking of a wideband sound and the loudspeaking of only a local space.
[0008]
An object of the present invention is to improve the above-described points and provide a method for realizing a small-scale reproduction of a sound in a local space and a reproduction of a wideband sound, which cannot be achieved by the existing technology. It is.
[0009]
[Means for Solving the Problems]
According to claim 1 of the present invention, an input signal is divided into a plurality of arbitrary frequency bands, a signal in any of the bands is reproduced by a primary sound source, and a signal in the same band reproduced by the primary sound source is reproduced. By controlling the delay and frequency characteristics of the secondary sound source as input signals for the secondary sound source and controlling the delay and frequency characteristics of the secondary sound source based on an output signal from a sensor arranged at the boundary of an arbitrary local space, the sound emitted outside the boundary And the amplitude of the sine wave in the ultrasonic band is modulated by the signal in the other frequency band obtained by dividing the frequency band, and the ultrasonic vibration element is excited by the amplitude-modulated ultrasonic signal to generate a signal in the other frequency band. We propose a method of local space loudspeaker that reproduces as sound.
[0010]
According to a second aspect of the present invention, in the local space loudspeaker method according to the first aspect, a sound in an arbitrary divided frequency band is reproduced, and based on an output of a sensor arranged on a boundary surface of the local space to be reproduced at the same time. Then, a local spatial loudspeaking method is proposed in which a signal to be output from a secondary sound source is generated and reproduced as sound so that the sound pressure and the sound pressure gradient at the position of the sensor are simultaneously made zero.
According to a third aspect of the present invention, in the local spatial loudspeaker method according to the first aspect, a part of a sample obtained by oversampling a sound in a frequency band reproduced by the ultrasonic vibration element is replaced with zero. In this case, a local spatial loudspeaker is proposed in which an ultrasonic vibration element is driven by a signal obtained by filtering a band component of a bandwidth to be reproduced from a signal containing the aliasing distortion component.
[0011]
According to a fourth aspect of the present invention, a frequency divider for dividing an input signal into a plurality of arbitrary frequency bands, and a signal in any of the bands divided by the frequency divider is reproduced as sound by a primary sound source. A signal in the same frequency band as the sound reproduced by the primary sound source is used as an input signal of the secondary sound source, and based on an output signal from a sensor arranged at a boundary of a local space where the sound is to be reproduced, a signal of the secondary sound source is generated. A low-frequency reproduction unit that controls delay and frequency characteristics to muffle sound emitted outside the boundary, and a sine of the ultrasonic band with a signal in a frequency band different from the frequency band of the sound reproduced by the low-frequency reproduction unit The present invention proposes a local spatial loudspeaker comprising a high-frequency range reproducing unit that modulates a wave, excites an ultrasonic transducer with the amplitude-modulated ultrasonic signal, and reproduces sound.
[0012]
According to a fifth aspect of the present invention, in the local spatial loudspeaker according to the fourth aspect, the low frequency range reproducing unit reproduces a signal in any one of the frequency bands divided by the frequency dividing unit as a sound. A sound source, a plurality of sensors arranged on a boundary surface of a local space in which a sound field is to be reproduced and detecting sound pressure and sound pressure gradient at each arrangement point, and the secondary sound source is detected by detection signals detected by the plurality of sensors. Local sound loudspeaker proposed by controlling the signal applied to the sound source and using an adaptive filter that reproduces the sound whose sound pressure and sound pressure gradient at the arrangement point of each sensor detected by a plurality of sensors are simultaneously zero to a secondary sound source. I do.
[0013]
According to a sixth aspect of the present invention, in the local space loudspeaker according to the fourth aspect, the high frequency range reproducing unit is provided with a plurality of ultrasonic vibration elements, and a focus at which each sound of the plurality of ultrasonic elements is focused on a low frequency. We propose a local space loudspeaker that reproduces the sound of the high-frequency range reproduction unit at the focal position by making the same within the local space sound field reproduced by the range reproduction unit.
According to a seventh aspect of the present invention, the first and second sound sources are described by a computer-readable code string, and the computer executes at least one of the local space loudspeaker methods according to the first to third aspects. We propose a local space loudspeaker program that generates drive signals to be applied to the ultrasonic transducers that make up the frequency range reproduction unit.
[0014]
According to an eighth aspect of the present invention, there is provided a recording medium comprising a computer-readable recording medium, wherein the local space loudspeaker program according to the seventh aspect is recorded.
Action <br/> it is possible to process the input signal according to the present invention a low frequency region and high frequency region individually by band division. In addition, a sound field control method using the property of the Kirchhoff-Helmholtz integral equation, which enables local reproduction in the low frequency range but cannot control in the high frequency range, and a sufficient sound field in the high frequency range A reproduction method using an ultrasonic parametric loudspeaker, which can reproduce with pressure but cannot reproduce with sufficient sound pressure in a low frequency range, is applied to signals in individual frequency bands. With this method, it is possible to achieve both reproduction of sound in a local space and reproduction of a wideband sound.
[0015]
Specifically, in the sound field control method using the property of the Kirchhoff-Helmholtz integral equation, a space including a reproduction speaker (primary sound source) is selected as an arbitrary closed space, and a sound pressure on a boundary surface of the space is selected. By controlling the output of the control speaker (secondary sound source) adaptively so that the sound pressure gradient (particle velocity) becomes zero, the sound is reproduced only in the closed space. On the other hand, in the method using the ultrasonic parametric loudspeaker, the audible sound is reproduced at one point in the local space by matching the focal points of the plural ultrasonic parametric loudspeakers to one point. By processing the signals divided for each frequency band and processing them by these two methods and then reproducing them in synchronization, it is possible to reproduce a wideband sound in an arbitrary local space.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an embodiment of a loudspeaker for a predetermined local space according to the present invention. A local spatial loudspeaker according to the present invention divides an input audio signal into a plurality of frequency band signals, and processes a low frequency band signal among the plurality of frequency band signals divided by the frequency dividing unit. A low-frequency range processing unit 20 that performs processing, a low-frequency range reproduction unit 40 that reproduces a signal in a low frequency band (for example, about several hundred Hz to 1 kHz) processed by the low frequency range processing unit 20 as sound,
A high frequency band processing unit 30 for processing a signal of a relatively high frequency band among a plurality of frequency band signals divided by the frequency dividing unit 10; and a high frequency band (1 kHz to 20 kHz) processed by the high frequency band processing unit 30. 3) shows a high frequency range reproducing unit 50 that reproduces the signal as a sound.
[0017]
The number of divisions of the frequency band signal to be divided by the frequency division unit 10 is arbitrary on each of the low frequency side and the high frequency side. Will be described.
FIG. 2 shows a specific example of the low frequency band processing unit 20 and the low frequency band reproducing unit 40. The low-frequency range processing unit 20 can be constituted by an adaptive filter 21, and the low-frequency range reproduction unit 40 includes a primary sound source 41, a secondary sound source 42, and a plurality of sound sources installed at boundaries of a local space in which a sound field is to be reproduced. And the sound pressure / sound pressure gradient sensor 43.
[0018]
The primary sound source 41 and the secondary sound source 42 can be specifically constituted by speakers. The embodiment shown in FIG. 2 shows a case where the primary sound source 41 is constituted by one speaker and the secondary sound source 42 is constituted by a plurality of speakers. FIG. 3 shows an example of a specific arrangement of the primary sound source and the secondary sound source. The example shown in FIG. 3 shows a case where sound from one primary sound source is controlled using seven secondary sound sources and six sound pressure / sound pressure gradient sensors 43. By placing the primary sound source 41 farther than the secondary sound source 42 or adding a delay to the primary sound source with respect to the sound pressure / sound pressure gradient sensor 43, the causality of the adaptive filter used for the secondary sound source is satisfied. be able to. Incidentally, the sound pressure / sound pressure gradient sensor 43 can be generally constituted by an acoustic-electrical signal converter, so-called microphone. In particular, the sound pressure gradient sensor is configured by arranging a pair of microphones close to each other, and detects a sound pressure gradient based on a sound pressure difference between sounds detected by the pair of microphones.
[0019]
The description returns to FIG. 2, the input x (t) from the frequency division unit 10 is convolved with the filter coefficient W (t) of the adaptive filter 21, and the result y (t) is output to the low frequency range reproduction unit 40. Is done. In the output sound, the sound pressure and the sound pressure gradient on the boundary surface are observed by the sound pressure / sound pressure gradient sensor 43 installed at the boundary of the local space to be reproduced, and the values are used on the boundary surface using the values. The filter coefficient W (t + 1) of the adaptive filter 21 to be used for the next output is determined so that the sound pressure and the sound pressure gradient become zero. The low frequency range processing units 20 are provided in a number corresponding to the number of the sound pressure / sound pressure gradient sensors 43 arranged on the boundary surface of the local space to be reproduced and the number of the speakers of the secondary sound source 42. Therefore, the update of the filter coefficient W (t + 1) of the adaptive filter 21 is performed, for example, by using the MEFX-LMS algorithm (Elliot et. Al, "A multiple error LMS algorithm and it's application to active control of ed. Speech Signal Proc., Vol. ASSP-35 (10), pp. 1423-1434, 1987.) or the like is used. In general, the MEFX-LMS algorithm is described as an algorithm for the case of the number of reference sensors (the number of inputs of the adaptive filter) K, the number of secondary sound sources L, and the number of control points (error sensors) M. , L, M]. In the embodiment shown in FIG. 2, since the input to the adaptive filter is one channel, CASE [1, L. M], the filter coefficients are updated.
[0020]
FIG. 4 shows a specific embodiment of the high frequency band processing unit 30 and the high frequency band reproducing unit 50. Generally, a configuration including the high frequency band processing unit 30 and the high frequency band reproducing unit 50 is called an ultrasonic parametric speaker.
The high frequency band processing unit 30 can be configured by an AD conversion unit 31, an addition unit 32, a DC bias generation unit 33, a distortion addition unit 34, a filtering unit 35, and a DA conversion unit 36.
The AD converter 31 oversamples the audible sound signal in the high frequency band input from the frequency divider 10 and performs AD conversion. When the upper limit frequency of the audible sound signal input from the frequency division unit 10 is fu, the sampling frequency fs is
fs = N · (2 · fu) (1)
N is given by a positive integer of 2 or more.
[0021]
Generally, the upper limit frequency fu of the audible frequency band is set to 20 kHz. Therefore, in the case of a general AD conversion operation such as when recording and reproducing an audible sound signal, the sampling frequency should be twice the upper limit frequency fu. Is enough. However, in this case, the sampling frequency fs is selected to be higher than, for example, N = 2, and the sampling frequency fs is selected to be fs = 2 × 2 × 20 kHz, and oversampling is performed.
A constant DC bias value is added to each sample of the oversampled high frequency band signal by the adding unit 32, and each sample to which the fixed value is added is input to the distortion adding unit 34.
[0022]
The distortion adding unit 34 can be configured by a zero value replacement unit 34A. The zero-value replacing unit 34A replaces at least some of the sample values in the sample sequence obtained by oversampling with zero values, thereby causing aliasing. As an example of replacement with a zero value, the value of a sample in a sample sequence is replaced with a zero value every Nth sample.
As shown in FIG. 5, due to the aliasing distortion, AU1, AU2, and AU3 are generated as aliasing noise of the carriers CY1, CY2 and the audible sound signal AU generated by the DC component.
[0023]
When N = 2 in the equation (1), the carrier CY2 has a frequency of 80 kHz, and the carrier CY1 is generated at a half frequency of 40 kHz due to aliasing. Further, the lower limit frequency f _L of the audible sound signal _AU, if the bandwidth was set to f _x, the signal component AU1 bandwidth has a component of 2FU-fu on acceleration side by aliasing in f _x, upper side having a component of the _{2FU-f L} to. Signal component AU2 have components with 2FU + _{f L} bandwidth the lower side _{f x,} having a component of 2FU + fu to the upper limit side. Signal component AU3 bandwidth has a component of 4fu-fu to the lower side at _{f x,} having a component of _{4fu-f L} to the upper limit side.
[0024]
Looking at these frequency components, the signal components AU1 and AU2 can be seen as a lower sideband and an upper sideband of an amplitude-modulated wave obtained by amplitude-modulating the carrier CY1 with the audible sound signal AU. The signal component AU3 can be seen as a lower sideband of an amplitude-modulated wave obtained by amplitude-modulating the carrier CY2 with the audible sound signal AU.
Therefore, in this embodiment, the band of the audible sound to be reproduced from the signal containing the aliasing distortion component in the filtering unit 35 from the upper limit frequency fu (20 kHz) or an even multiple (40 kHz, 80 kHz) of the audible sound signal AU. configured to to retrieve or width f _x, or the band components of bandwidth twice that by filtering. That is, for example, the carrier CY1, the signal component AU1, and the signal component AU2 are filtered out as shown in FIG. 6A, or the carrier CY1 and the signal component AU1 are filtered out as shown in FIG. As shown in FIG. 6C, the carrier CY1 and the signal component AU2 are filtered and extracted, and the filtered and extracted signal is DA-converted by the DA converter 36, and the analog signal is output to the high frequency range reproducing unit 50.
[0025]
The high frequency range reproducing unit 50 can be constituted by an amplifier 51 and an ultrasonic vibration element group 52. By driving the ultrasonic vibration element group 52 with the signal amplified by the amplifier 51, an ultrasonic wave having the frequency of the carrier CY1 or CY2 can be generated. Since the amplitude is modulated by the audible signal in the high frequency range divided by 10, the audible sound is reproduced in the propagation process of the ultrasonic wave.
By mounting the ultrasonic vibration element group 52 on a concave plate, for example, and setting the focal point of the concave surface to a desired distance, a strong audible sound can be reproduced at the focal position.
[0026]
FIG. 7 shows the relationship between the arrangement of the low frequency band reproducing unit 40 and the high frequency band reproducing unit 50 and the sound field of the reproduced sound. Here, a plurality (three in the example shown in FIG. 7) of the high-frequency band reproducing units 50 are provided, and the focal positions of the high-frequency band reproducing units 50 are matched within the low-frequency band reproduction sound field Low, thereby making the low-frequency band reproduction sound field Low low. A high frequency range sound field High can be generated in the sound field Low.
The frequency division unit 10, the low frequency band processing unit 20, and the high frequency band processing unit 30 described above can be configured by a computer. By causing a computer to execute the above-described frequency division processing, low frequency range processing, and high frequency range processing by a program, and to generate a drive signal for driving the low frequency range reproduction unit 40 and the high frequency range reproduction unit 50, It is possible to realize the local space loudspeaking method according to the invention.
[0027]
The program is recorded on a computer-readable recording medium such as a magnetic disk or a CD-ROM, and is installed in the computer from the recording medium or installed in the computer through a communication line, and is decoded by a CPU built in the computer. Then, the above-mentioned local space loudspeaking method is executed.
[0028]
【The invention's effect】
As described above, according to the present invention, an input signal tone is divided into frequency bands, and processed using a different method for each band, and then reproduced. It is possible to reproduce with sufficient sound pressure in a wide frequency band over a frequency range, and at the same time, it is possible to reproduce sound only in an arbitrary local space while being small. That is, the local reproduction and the broadband reproduction, which could not be achieved at the same time, can be simultaneously realized by a small-scale system.
[Brief description of the drawings]
FIG. 1 is a block diagram for explaining the overall configuration of the present invention.
FIG. 2 is a block diagram for explaining a specific example of a high frequency band processing unit and a low frequency band reproducing unit shown in FIG. 1;
FIG. 3 is an arrangement diagram for explaining an example of a more detailed arrangement of the low frequency band reproduction section shown in FIG. 2;
FIG. 4 is a block diagram for explaining a specific example of a high frequency band processing unit and a high frequency band reproducing unit shown in FIG. 1;
FIG. 5 is a graph for explaining the operation of the high frequency band processing section shown in FIG. 4;
FIG. 6 is a graph similar to FIG. 5 for explaining the operation of the high frequency band processing unit shown in FIG. 4;
FIG. 7 is a layout diagram for explaining the overall operation of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Frequency division part 41 Primary sound source 20 Low frequency processing part 42 Secondary sound source 21 Adaptive filter 43 Sound pressure / sound pressure gradient sensor 30 High frequency processing part 50 High frequency reproduction part 40 Low frequency reproduction part 52 Ultrasound Vibration element group

Claims (8)

The input signal is divided into a plurality of arbitrary frequency bands, a signal in any of the bands is reproduced by a primary sound source, and a signal in the same band reproduced by the primary sound source is input to a secondary sound source. And controlling the delay and frequency characteristics of the secondary sound source based on an output signal from a sensor arranged at the boundary of an arbitrary local space, thereby muting sound emitted outside the boundary, and controlling the frequency The sine wave in the ultrasonic band is amplitude-modulated with the signal of the other frequency band obtained by band division, and the ultrasonic vibration element is excited by the amplitude-modulated ultrasonic signal to reproduce the signal of the other frequency band as sound. A local spatial vocalization method characterized by the following. 2. The local space loudspeaker method according to claim 1, wherein a sound in an arbitrary divided frequency band is reproduced, and based on an output of a sensor arranged on a boundary surface of the local space to be reproduced at the same time, a sound at a position of the sensor is obtained. A local spatial vocalization method characterized by generating a signal to be output from a secondary sound source so as to simultaneously reduce the sound pressure and the sound pressure gradient to zero and reproducing the signal as sound. 2. The local spatial loudspeaker method according to claim 1, wherein aliasing distortion is obtained by replacing a part of a sample obtained by oversampling with a sound in a frequency band reproduced by the ultrasonic vibration element with zero. A local spatial sounding method in which an ultrasonic vibration element is driven by a signal obtained by filtering a band component of a bandwidth to be reproduced from a signal including the aliasing distortion component. A frequency division unit that divides the input signal into an arbitrary plurality of frequency bands,
A signal in any of the bands divided by the frequency division unit is reproduced as sound by the primary sound source, and a signal in the same frequency band as the sound reproduced by the primary sound source is used as an input signal of the secondary sound source to reproduce the sound. A low-frequency range reproduction unit that controls the delay and frequency characteristics of the secondary sound source based on an output signal from a sensor arranged at the boundary of the local space to be processed, and mutes a sound emitted outside the boundary,
The sine wave in the ultrasonic band is amplitude-modulated with a signal in a frequency band different from the frequency band of the sound reproduced by the low-frequency band reproducing unit, and the ultrasonic vibration element is excited by the amplitude-modulated ultrasonic signal, and the sound is excited. A high frequency range reproducing unit for reproducing
A local space loudspeaker characterized by comprising: The local space loudspeaker according to claim 4, wherein the low frequency band reproduction unit comprises:
A primary sound source and a secondary sound source for reproducing a signal in any one of the frequency bands divided by the frequency dividing unit as sound;
A plurality of sensors arranged on the boundary surface of the local space to reproduce the sound field and detecting sound pressure and sound pressure gradient at each arrangement point,
A signal given to the secondary sound source is controlled by a detection signal detected by the plurality of sensors, and a sound in which the sound pressure and the sound pressure gradient at the arrangement point of each sensor detected by the plurality of sensors are simultaneously zero is set to the secondary sound. An adaptive filter to be played by the sound source;
A local space loudspeaker characterized by comprising: 5. The local spatial loudspeaker according to claim 4, wherein said high frequency band reproducing unit is equipped with a plurality of ultrasonic vibrating elements, and said low frequency band reproducing unit reproduces a focal point of each sound of said plurality of ultrasonic elements. A local spatial loudspeaker, which reproduces the sound of the high-frequency range reproducing unit at the focal position in the local spatial sound field. A computer which is described by a code string which can be decoded, and causes the computer to execute at least one of the local spatial loudspeaker methods according to claims 1 to 3 to constitute the primary sound source, the secondary sound source, and the high frequency band reproducing unit. Local space loudspeaker program for generating a drive signal to be applied to a vibrating ultrasonic transducer. A recording medium comprising a computer-readable recording medium, wherein the local space sound enhancement program according to claim 7 is recorded.

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