WO2014077234A1

WO2014077234A1 - Sound system and electronic equipment

Info

Publication number: WO2014077234A1
Application number: PCT/JP2013/080505
Authority: WO
Inventors: 黒田　淳; 康晴大西; 重夫佐藤
Original assignee: Ｎｅｃカシオモバイルコミュニケーションズ株式会社
Priority date: 2012-11-13
Filing date: 2013-11-12
Publication date: 2014-05-22

Abstract

Provided is a sound system by which sound image localisation can be clearly sensed when reproducing a stereo sound source. The sound system includes a parametric speaker array, a first amp, a second amp, and a digital signal processing device. The parametric speaker array is configured to include a plurality of parametric speakers. The first amp drives the parametric speakers included in a first region of the parametric speaker array. The second amp drives the parametric speakers included in a second region of the parametric speaker array. The digital signal processing device generates a first modulation signal to supply to the first amp, and a second modulation signal to supply to the second amp, by modulating a carrier wave of an ultrasonic region on the basis of a plurality of audio signals.

Description

Acoustic system and electronic equipment

[Description of related applications]
The present invention is based on a Japanese patent application: Japanese Patent Application No. 2012-249068 (filed on November 13, 2012), and the entire description of the application is incorporated herein by reference.
The present invention relates to an acoustic system and an electronic device. In particular, the present invention relates to an acoustic system including a parametric speaker and an electronic apparatus.

In recent years, research and development of products using parametric speakers with high directivity (so-called ultrasonic speakers) are progressing. An acoustic system including a parametric speaker can be heard only at a target place (spot), and thus can be expected to be used in a noisy situation.

Here, Patent Document 1 discloses a projector that controls the radiation characteristics of an ultrasonic speaker so that the acoustic characteristics (realism) do not change greatly even if the size of the projected image varies.

JP 2006-025108 A

It should be noted that the disclosure of the above prior art document is incorporated herein by reference. The following analysis was made by the present inventors.

Electronic devices such as mobile phones and smartphones are equipped with speakers for providing voice to users. Such a speaker does not cause a problem when monaural (one channel) sound is reproduced. However, there is a problem in reproducing stereo (two-channel) sound in an electronic device having a normal speaker. This is because the housing of a smartphone or the like is small and it is difficult to secure a distance between a speaker that reproduces L-channel sound and a speaker that reproduces R-channel sound.

If the distance between the two speakers cannot be secured, the user cannot feel as if the sound is clearly separated into left and right (the left and right sound image localization is felt indistinct). Such a problem does not occur in a large electronic device such as a projector disclosed in Patent Document 1. This is because the distance between the two speakers can be secured.

In view of the above situation, an acoustic system and an electronic device that can clearly feel the left and right localization of a sound image when a stereo sound source is reproduced are desired.

According to a first aspect of the present invention, a parametric speaker array configured to include a plurality of parametric speakers, a first amplifier that drives a parametric speaker included in a first region of the parametric speaker array, and A second amplifier for driving a parametric speaker included in the second region of the parametric speaker array, and a first amplifier supplied to the first amplifier by modulating a carrier wave in the ultrasonic region based on a plurality of audio signals. There is provided an acoustic system including a digital signal processing device that generates one modulation signal and a second modulation signal to be supplied to the second amplifier.

According to a second aspect of the present invention, an electronic device including the acoustic system is provided.

According to each viewpoint of the present invention, an acoustic system and an electronic device that contribute to clearly feeling the left and right localization of a sound image when a stereo sound source is reproduced are provided.

It is a figure for demonstrating the outline | summary of one Embodiment. 1 is a diagram illustrating an example of a cross section of a parametric speaker 10. FIG. It is a figure which shows an example of the parametric speaker array 20 which arranged the some parametric speaker 10 in the array form. 1 is a diagram illustrating an example of a configuration of an acoustic system including a parametric speaker array 20. FIG. FIG. 5 is a diagram illustrating an example of a sound pressure distribution when an ultrasonic carrier wave is radiated from the parametric speaker array 20 in the acoustic system illustrated in FIG. 4. It is a figure which shows an example of a sound pressure distribution map. It is a figure which shows an example of the internal structure of the acoustic system which concerns on 1st Embodiment. It is a figure which shows another example of the internal structure of the acoustic system which concerns on 1st Embodiment. It is a figure which shows an example of the internal structure of the acoustic system corresponding to a multichannel.

First, an outline of an embodiment will be described with reference to FIG. Note that the reference numerals of the drawings attached to the outline are attached to the respective elements for convenience as an example for facilitating understanding, and the description of the outline is not intended to be any limitation.

As described above, when a stereo sound source is reproduced, an acoustic system in which the left and right localization of a sound image can be clearly sensed and an electronic device including such an acoustic system are desired.

Therefore, the acoustic system shown in FIG. 1 is provided as an example. The acoustic system shown in FIG. 1 includes a parametric speaker array 100, a first amplifier 101, a second amplifier 102, and a digital signal processing device 103. The parametric speaker array 100 includes a plurality of parametric speakers. The first amplifier 101 drives parametric speakers included in the first region of the parametric speaker array 100. The second amplifier 102 drives a parametric speaker included in the second region of the parametric speaker array 100. The digital signal processing device 103 modulates a carrier wave in the ultrasonic region based on a plurality of audio signals, thereby providing a first modulation signal to be supplied to the first amplifier 101 and a second modulation signal to be supplied to the second amplifier 102. 2 modulation signals.

As described above, the size of the housing of an electronic device such as a smartphone is limited. Therefore, reproduction of a stereo sound source using a normal speaker is difficult. However, since the parametric speaker has high directivity, it is possible to restore sound (sound source audible) at a specific spot. Therefore, by using a plurality of parametric speakers, the sound pressure required for practical use is secured, and by arranging them, the area required for installing the speakers is reduced. Further, the area of the parametric speaker array is divided into first and second areas, and the reproduction of the L channel audio signal and the R channel audio signal is assigned to each area. As a result, sound waves are emitted toward the left ear from the parametric speaker included in the first region, and sound waves are emitted toward the right ear from the parametric speaker included in the second region. Then, due to the high directivity of the parametric speaker, there is little mixing in the left and right audible sounds, and the user can clearly sense the left and right localization of the sound image.

Next, prior to the description of a specific embodiment, an acoustic system including a parametric speaker will be described.

FIG. 2 is a diagram showing an example of a cross section of the parametric speaker 10. Referring to FIG. 2, the parametric speaker 10 is configured by adhering a metal cone 13 to a vibration plate in which a piezoelectric element 11 and a metal plate 12 are bonded. An adhesive 14 is used for bonding the metal plate 12 and the metal cone 13. The diaphragm is fixed to the frame 16 via the elastic material 15. A signal for vibrating the diaphragm is supplied from the terminal 17.

FIG. 3 is a diagram showing an example of a parametric speaker array 20 in which a plurality of parametric speakers 10 are arranged in an array. The parametric speaker array 20 shown in FIG. 3 is formed by arranging sixteen parametric speakers 10 horizontally and two vertically.

As described above, parametric speakers have extremely high directivity. It can be understood from the sound pressure distribution diagram of FIG. 5 that the parametric speaker exhibits high directivity. Details of FIG. 5 will be described later.

Next, the configuration of an acoustic system including the parametric speaker array 20 will be described. FIG. 4 is a diagram illustrating an example of the configuration of an acoustic system including the parametric speaker array 20. Note that the sound system shown in FIG. 4 is based on the reproduction of a monaural sound source.

The acoustic system includes a CPU (Central Processing Unit) 30, a DSP (Digital Signal Processing) 40, a DA (Digital Signal Processing) converter 50, an audio amplifier 60, and a parametric speaker array 20. . The parametric speaker array 20 is driven by each module (circuit block) shown in FIG.

Further, the CPU 30 includes a data loader 31 and a decoder 32. The data loader 31 is means for reading an audio signal from an external storage (for example, an SD card, a hard disk, a flash memory, etc.). Note that audio signals stored in an external storage are often compressed by MPEG (Moving / Pictures / Experts / Group) or the like. A means for decoding such a compressed audio signal is the decoder 32. The CPU 30 outputs an audio signal to the DSP 40.

The DSP 40 includes an upsampling unit 41, an ultrasonic carrier wave generation unit 42, and a modulation processing unit 43.

The DSP 40 uses the upsampling unit 41 to upsample the audio signal decoded by the decoder 32. A sampling rate of 48 kHz or less is often used for audio signals stored in an SD card or the like. Therefore, the upsampling unit 41 needs to upsample to a frequency higher than 48 kHz such as 192 kHz or 96 kHz. The reason is that a carrier wave in an ultrasonic region that is a frequency region higher than the audible band (for example, 40 kHz or more) is used. In the following description, the carrier in the ultrasonic region is referred to as an ultrasonic carrier.

Also, when determining whether to select either 192 kHz or 96 kHz as the sampling rate, the Nyquist frequency of the sampling rate is considered. More specifically, the sampling rate is selected such that the frequency of the ultrasonic carrier wave has a sufficient margin with respect to the Nyquist frequency of the sampling rate and is equal to or lower than the Nyquist frequency.

The modulation processor 43 modulates the ultrasonic carrier wave generated by the ultrasonic carrier wave generator 42 with the upsampled audio signal. For example, FM (Frequency modulation), AM (Amplitude modulation), SSB (Single side band modulation), or the like can be used as the modulation method at that time. The DSP 40 outputs the signal modulated by the modulation processing unit 43 to the DA converter 50.

The DA converter 50 converts the received signal into an analog signal and outputs it to the audio amplifier 60.

The audio amplifier 60 amplifies the modulated signal converted into the analog signal to an appropriate power and supplies it to the parametric speaker array 20. The parametric speaker array 20 is driven by the audio amplifier 60, and sound waves are radiated into the space.

When the audio amplifier 60 is a digital amplifier (for example, a class D amplifier), a low pass filter (not shown) is inserted between the audio amplifier 60 and the parametric speaker array 20 in order to remove the oscillation frequency of the digital amplifier. To do.

FIG. 5 is a diagram showing an example of a sound pressure distribution when an ultrasonic carrier wave is radiated from the parametric speaker array 20 in the acoustic system shown in FIG. In FIG. 5, the parametric speaker array 20 is arranged at the center of the figure, and the sound pressure distribution in the two-dimensional space is expressed by color shading. It shows that the sound pressure is higher in the darker region than in the lighter region.

Referring to FIG. 5, strong directivity can be confirmed in the direction in which the parametric speaker array 20 faces (Y-axis direction in FIG. 5). The conditions for driving the parametric speaker array 20 are, for example, as follows.
・ The frequency of the ultrasonic carrier wave is 80 kHz.
-The size of the parametric speaker array 20 shall be 1.8 cm x 7.2 cm.
The ultrasonic wave emission surface is in the Y-axis direction in FIG. 5 (upward in FIG. 5).

Here, the sound waves radiated from the individual parametric speakers 10 constituting the parametric speaker array 20 modulate an ultrasonic carrier wave using an audio signal output from the CPU 30. Therefore, Fourier components other than the frequency of the ultrasonic carrier wave are included. However, in the modulation method of AM modulation, FM modulation, or SSB modulation, by using a modulation parameter (for example, modulation degree, modulation index) suitable for driving the parametric speaker 10, energy of Fourier components other than the carrier wave is converted to the carrier wave. 1/5 or less of the energy. Therefore, the directivity of the ultrasonic carrier wave can be understood as the directivity of the entire modulated wave.

In FIG. 5, a region 200 is a region where the sound pressure of the ultrasonic carrier wave is higher than that of other regions by 10 dB or more. Therefore, it can be said that the region 200 is a region where the audible sound is demodulated almost as it is. If the same signal is input to all of the parametric speakers 10 included in the parametric speaker array 20, a monaural audible sound is heard by the user as shown in FIG.

Hereinafter, specific embodiments will be described in more detail with reference to the drawings.

[First Embodiment]
The first embodiment will be described in more detail with reference to the drawings.

In the acoustic system according to the present embodiment, when the audio signal of a stereo sound source is demodulated to an audible sound with high directivity (narrow directivity), good left and right panning ( Realize high sound image localization on the left and right.

The acoustic system according to the present embodiment uses a parametric speaker array 20 in which a plurality of parametric speakers 10 are arranged in an array as shown in FIG. The parametric speaker array 20 is mounted on a substrate (on a plane) used for a smartphone or the like, for example. The number of parametric speakers 10 constituting the parametric speaker array 20 may be arbitrary, but is preferably 50 or less in consideration of mounting area, cost, and the like.

For example, consider the case of using a parametric speaker array 20 including 16 parametric speakers 10 as shown in FIG. In this case, among the 16 parametric speakers 10, the left half 8 parametric speakers 10 have an L channel, the right half 8 parametric speakers 10 have an R channel, and the final ultrasonic radiation source. Use as That is, the parametric loudspeaker array is divided into first and second areas, and the respective areas are assigned to play audio signals of the L channel and the R channel.

FIG. 6 is a diagram showing an example of a sound pressure distribution diagram. FIG. 6 shows a sound pressure distribution when an ultrasonic carrier wave of 80 kHz is radiated from the right half, that is, eight R channel parametric speakers 10. Referring to FIG. 6, an ultrasonic audible band 201 (a region where the sound pressure of the ultrasonic carrier is about 10 dB higher than other regions) is formed in front of the parametric speaker for the R channel (upper side in FIG. 6). I understand that. That is, FIG. 6 shows that the modulated waves of the L channel and the R channel can be separated into left and right (LR separation), and it is possible to separate stereo sound sources in the audible band.

Further, it has been found by the inventors that the stereo sound source separation is extremely clear when the stereo mounted on a mobile phone, a tablet terminal, a smartphone or a television device is compared with a speaker. More specifically, it is close to the case where a stereo sound source is viewed using headphones.

FIG. 7 is a diagram illustrating an example of the internal configuration of the acoustic system according to the present embodiment. In the acoustic system shown in FIG. 7, stereo processing is performed from reading of a sound source to driving of a parametric speaker. This is the difference between the acoustic system shown in FIG. 4 and the acoustic system shown in FIG.

7 is not different from the CPU 30 except that the internal modules (the data loader 31a and the decoder 32a) are compatible with stereo sound sources, and further description thereof is omitted. The DA converters 50-1 and 50-2, the audio amplifiers 60-1 and 60-2, and the parametric speaker arrays 20-1 and 20-2 are also modules provided corresponding to stereo sound sources, respectively. Since the individual functions are not different from the modules already described, further description is omitted. The audio amplifier 60-1 may be configured to drive the parametric speakers included in the parametric speaker array 20-1 in common, or may be configured to individually drive the parametric speakers. The same applies to the audio amplifier 60-2.

The DSP 40a is also configured to support a stereo sound source. The upsampling unit 41 performs upsampling on a stereo audio signal. The left and right up-sampled audio signals are respectively subjected to modulation processing by the modulation processing units 43-1 and 43-2. The DSP 40a corresponds to the digital signal processing device 103 described above.

The signal modulated by the modulation processing unit 43-1 is output to the multipliers 44-1 and 44-4. The signal modulated by the modulation processing unit 43-2 is output to the multipliers 44-2 and 44-3. The multiplication coefficients of the multipliers 44-1 to 44-4 are as follows.
- multiplier 44-1 comprises a multiplier factor of _{X L.}
Multiplier 44-2 includes a multiplier coefficient _{1-X L.}
Multiplier 44-3 includes a multiplier coefficient _{X R.}
Multiplier 44-4 includes a multiplier coefficient _{1-X R.}
In this way, the multipliers 44-1 to 44-4 multiply the amplitude of the upsampled stereo audio signal by a predetermined coefficient. X _L and X _R can be regarded as parameters for controlling panning.

The calculation results by the multipliers 44-1 and 44-2 are sent to the adder 45-1. The calculation results by the multipliers 44-3 and 44-4 are sent to the adder 45-2. The calculation result of the adder 45-1 is output to the DA converter 50-1 as a modulation signal for the L channel. The calculation result of the adder 45-2 is output to the DA converter 50-2 as a modulation signal for the R channel. The L channel modulation signal corresponds to the first modulation signal described above, and the R channel modulation signal corresponds to the second modulation signal described above.

The processing in the DSP 40a can be expressed by the following equation (1).

Incidentally, _{U L} and _{U R} are input signals to DSP40a. Y _L and _{Y R} are the output signals from the DSP40a. Referring to equation (1), according to the value of X _L and X _R, it is understood that can control the panning of the sound source.

The DSP 40a generates a modulation signal to be supplied to the audio amplifiers 60-1 and 60-2 that drive the parametric speaker arrays 20-1 and 20-2 according to the equation (1).

Localization of a sound image to be reproduced by a parametric speaker array 20-1 and 20-2 are adjustable (controlled) by changing the _{X L} and _{X R} in Formula (1). The range of changing the value of _{X L} and _{X R} is, 1/2 ≦ _X L, and _{X R} ≦ 1. For example, when the both X _L and X _R "1", the sound image is localized as faithful stereo signals to the sound source. Also, if both X _L and X _R "1/2", the sound image as in the monophonic sound source is localized.

Further, in an electronic device such as a mobile phone or a smartphone that includes the acoustic system shown in FIG. 7, it is usual to include a control unit that controls the entire electronic device. The DSP 40a is configured to be able to change the internal coefficient from the outside, and the control unit of the electronic device can change the multiplication coefficient of the multipliers 44-1 to 44-4. For this reason, it is preferable to change the coefficient in conjunction with the type of content to be played back on the electronic device. For example, it is possible to provide a user with sound image localization that faithfully reproduces a stereo sound source, or to provide a stereo sound source to the user in a form close to a monaural sound source, depending on the situation in which the electronic device is used. .

Alternatively, panning (sound image localization) can be controlled by changing the coefficient in conjunction with the moving image displayed on the display as well as the sound.

Note that the internal configuration of the DSP 40a shown in FIG. 7 is an example, and is not intended to limit the configuration of the DSP 40a. As shown in FIG. 8, the processing corresponding to Equation (1) is executed (calculations by multipliers 44-1 to 44-4 and adders 45-1 and 45-2), and then the stereo audio signal is modulated. May be.

Alternatively, it can be assumed that the sound source is not a stereo but a multi-channel sound source. For example, a specific sound may be rendered in the left and right localization.

FIG. 9 is a diagram illustrating an example of an internal configuration of an acoustic system that supports multi-channel. In FIG. 9, each module of the data loader 31b, the decoder 32b, the upsampling unit 41a, and the modulation processing unit 43a is associated with a multi-channel sound source. Then, the L channel modulation signal and the R channel modulation signal may be generated by the LR mixer 46 that executes the processing of the following equation (2).

Note that a1 to an and b1 to bn (where n is a natural number) are coefficients that are multiplied when mixing (mixing) the input signals U1 to Un when generating a modulation signal.

The acoustic system according to the present embodiment can be mounted on electronic devices such as a mobile phone, a portable audio player, a television device, a tablet terminal, and a game machine.

As described above, the region of the parametric speaker array composed of a plurality of parametric speakers is separated into an L channel region and an R channel region. Further, a modulation signal for driving the parametric speaker included in each separated region is generated from the stereo sound source, and the directivity of the sound wave radiated from the parametric speaker array is controlled using the DSP. As a result, it is possible to provide an acoustic system and an electronic device that contribute to clearly feeling the left and right localization of a sound image when content having a stereo sound source is reproduced.

Some or all of the above embodiments may be described as in the following supplementary notes, but are not limited to the following.

[Appendix 1]
The sound system according to the first aspect is as described above.
[Appendix 2]
The digital signal processing device includes:
The result of multiplying the first modulated signal by the first coefficient to the amplitude of the first audio signal included in the plurality of audio signals and the amplitude of the second audio signal included in the plurality of audio signals. A result obtained by multiplying the second coefficient is added to
Adding the result of multiplying the amplitude of the first audio signal by a third coefficient to the amplitude of the first audio signal and the result of multiplying the amplitude of the second audio signal by a fourth coefficient. The acoustic system of Supplementary Note 1 generated by
[Appendix 3]
The digital signal processing device includes:
The acoustic system according to appendix 1 or 2, wherein the plurality of audio signals are up-sampled to a sampling rate in an ultrasonic region, and a carrier wave in the ultrasonic region is modulated based on the plurality of up-sampled audio signals.
[Appendix 4]
The acoustic system according to appendix 2 or 3, wherein the first to fourth coefficients can be changed from outside the digital signal processing device.
[Appendix 5]
The acoustic system according to any one of appendices 2 to 4, wherein the values of the first and third coefficients are 0.5 or more and 1 or less, respectively.
[Appendix 6]
The digital signal processing device includes:
The acoustic system according to appendix 1, wherein the first and second modulated signals are generated by multiplying each of the plurality of audio signals by a predetermined coefficient and adding the multiplication results.
[Appendix 7]
As in the electronic apparatus according to the second aspect.

In addition, the disclosure of the cited patent document is incorporated herein by reference. Within the scope of the entire disclosure (including claims) of the present invention, the embodiments and examples can be changed and adjusted based on the basic technical concept. Various disclosed elements (including each element of each claim, each element of each embodiment or example, each element of each drawing, etc.) within the scope of the claims of the present invention, Selection is possible. That is, the present invention of course includes various variations and modifications that could be made by those skilled in the art according to the entire disclosure including the claims and the technical idea. In particular, with respect to the numerical ranges described in this document, any numerical value or small range included in the range should be construed as being specifically described even if there is no specific description.

DESCRIPTION OF SYMBOLS 10 Parametric speaker 11 Piezoelectric element 12 Metal plate 13 Metal cone 14 Adhesive 15 Elastic material 16 Frame 17 Terminal 20, 20-1, 20-2, 100

Parametric speaker array

30, 30a, 30b CPU (Central Processing Unit)
31, 31a,

31b Data loader

32, 32a,

32b Decoder

40, 40a, 40b DSP (Digital Signal Processor)
41, 41a Upsampling unit 42 Ultrasonic carrier wave generating units 43, 43-1, 43-2, 43a Modulation processing units 44-1 to 44-4 Multipliers 45-1, 45-2 Adder 46 LR mixers 50, 50 -1, 50-2 DA converters 60, 60-1, 60-2

Audio amplifier

101, 102 Amplifier 103 Digital

signal processing device

200, 201

Claims

A parametric speaker array including a plurality of parametric speakers;
A first amplifier for driving a parametric speaker included in the first region of the parametric speaker array;
A second amplifier for driving a parametric speaker included in a second region of the parametric speaker array;
A first modulation signal supplied to the first amplifier and a second modulation signal supplied to the second amplifier by modulating a carrier wave in the ultrasonic region based on a plurality of audio signals. A digital signal processing device to generate;
Including acoustic system.
The digital signal processing device includes:
The result of multiplying the first modulated signal by the first coefficient to the amplitude of the first audio signal included in the plurality of audio signals and the amplitude of the second audio signal included in the plurality of audio signals. A result obtained by multiplying the second coefficient is added to
Adding the result of multiplying the amplitude of the first audio signal by a third coefficient to the amplitude of the first audio signal and the result of multiplying the amplitude of the second audio signal by a fourth coefficient. The acoustic system according to claim 1, which is generated by:
The digital signal processing device includes:
The acoustic system according to claim 1 or 2, wherein the plurality of audio signals are up-sampled to a sampling rate of an ultrasonic region, and a carrier wave of the ultrasonic region is modulated based on the plurality of up-sampled audio signals.
4. The acoustic system according to claim 2, wherein the first to fourth coefficients can be changed from outside the digital signal processing device.
The acoustic system according to any one of claims 2 to 4, wherein the values of the first and third coefficients are 0.5 or more and 1 or less, respectively.
The digital signal processing device includes:
The acoustic system according to claim 1, wherein the first and second modulated signals are generated by multiplying each of the plurality of audio signals by a predetermined coefficient and adding the results of the multiplication.
Electronic equipment including the acoustic system according to any one of claims 1 to 6.