JP7609070B2 - Sound projection system - Google Patents

Description

This technology relates to a sound emission system, and in particular to a sound emission system that makes it difficult to hear sounds that leak outside a specified direction.

For example, in display exhibits such as advertisements, there is a need to ensure that audio can only be heard from within the visible area of the display, so as not to disturb the surrounding area.

When using a normal speaker to emit sound, the emitted sound can sometimes be diffused and leak into the surrounding area, making it seem noisy.

In such cases, sound dispersion can be minimized by using a system that uses multiple speakers to create directionality, such as a line array speaker.

Line array speakers are a technology that has already been commercialized by various companies, and by arranging multiple speakers in a line, it is possible to create directivity in the vertical direction of the speaker row. There are also some array-shaped speakers that use signal processing technology to further control the directivity.

Furthermore, technology has been proposed that uses array speakers to control directivity through signal processing (see, for example, Patent Documents 1 and 2).

JP 2006-115396 A JP 2011-41023 A

However, even when using line array speakers and the directional control achieved through signal processing using these speakers, although a sharp directivity is formed at the center of the line array speaker, the directivity at the edges of the array speaker becomes weaker than at the center, and the sound tends to diffuse.

This is because directivity is formed by the interaction of multiple speakers; for example, if a line array speaker is installed horizontally to the ground, there is no speaker at the right end of the line array speaker that can affect the sound that diffuses to the right.

Due to this principle, if a line array speaker is installed horizontally, sound will leak (scatter) from the right and left ends.

This technology was developed in consideration of such circumstances, and makes it harder to hear sounds that leak outside the specified direction.

A sound emission system according to one aspect of the present technology includes one or more first speakers that emit a target sound, one or more second speakers that are arranged adjacent to the one or more first speakers and emit a directional concealment sound, and a plurality of microphones that pick up environmental sounds in the vicinity of an area where the concealment sound is emitted, and the one or more second speakers emit the concealment sound based on a concealment sound signal selected from a plurality of concealment sound signals obtained based on a plurality of environmental sound signals that have been picked up in advance by the microphones at different times from one another, based on the environmental sound signal picked up by the microphones.

In one aspect of the present technology, a target sound is emitted by one or more first speakers, a directional concealment sound is emitted by one or more second speakers arranged adjacent to the one or more first speakers, and environmental sounds in the vicinity of an area where the concealment sound is emitted are picked up by a plurality of microphones. Also, the one or more second speakers emit the concealment sound based on the concealment sound signal selected from a plurality of concealment sound signals obtained based on a plurality of environmental sound signals previously picked up by the microphone at different timings, based on the environmental sound signal picked up by the microphone.

FIG. 1 is a diagram illustrating a configuration example of a sound emission system. FIG. 1 is a diagram illustrating sound leakage. 11 is a flowchart illustrating a playback process. FIG. 1 is a diagram illustrating a configuration example of a sound emission system. FIG. 1 is a diagram illustrating sound leakage. FIG. 1 is a diagram illustrating a configuration example of a sound emission system. FIG. 1 is a diagram illustrating sound leakage. 11 is a flowchart illustrating a playback process. 11 is a flowchart illustrating a playback process. 10A and 10B are diagrams illustrating correction of frequency characteristics of an array speaker. 10A and 10B are diagrams illustrating correction of the frequency characteristics of a microphone. FIG. 1 illustrates an example of the configuration of a computer.

Below, we will explain an embodiment of the present technology with reference to the drawings.

First Embodiment
<Example of sound projection system configuration>
(Plays pre-recorded concealed audio)
This technology is intended to make it difficult to sense sounds leaking outside the direction of direction in a sound emission system that uses one or more speakers, such as a line array speaker, to form directivity.

With this technology, for example, sound leaking from the end of a line array speaker can be made to sound similar to the sound in the area where the leaking sound is heard, or sound picked up in that area, making it difficult to distinguish from the sound in that area and making it difficult for listeners to sense that the sound is leaking.

Figure 1 is a diagram showing an example configuration of one embodiment of a sound emission system to which the present technology is applied.

The sound output system 11 shown in Figure 1 has an audio player 21-1, an audio player 21-2, an audio player 22, an audio amplifier 23-1, an audio amplifier 23-2, an audio amplifier 24, an array speaker 25-1, an array speaker 25-2, and an array speaker 26.

In audio player 21-1 and audio player 21-2, a concealment sound signal, which is an audio signal of pre-recorded environmental sounds, is recorded. Here, the pre-recorded environmental sounds are used as concealment sounds to make sound leakage less perceptible.

Audio player 21-1 and audio player 21-2 start playing audio in response to a playback start signal or button operation (not shown), and output an analog or digital concealment sound signal to audio amplifier 23-1 and audio amplifier 23-2.

Audio amplifier 23-1 and audio amplifier 23-2 amplify the concealment sound signals supplied from audio reproducer 21-1 and audio reproducer 21-2, and drive array speaker 25-1 and array speaker 25-2 based on the amplified concealment sound signals to emit the concealment sounds.

In the following, when there is no need to particularly distinguish between audio player 21-1 and audio player 21-2, they will simply be referred to as audio player 21.

Furthermore, hereinafter, when there is no need to distinguish between audio amplifier 23-1 and audio amplifier 23-2, they will simply be referred to as audio amplifier 23, and when there is no need to distinguish between array speaker 25-1 and array speaker 25-2, they will simply be referred to as array speaker 25.

The audio player 22 stores a target sound signal, which is an audio signal of a target sound, such as a pre-recorded explanation of an advertisement to be displayed. The target sound is the sound that is desired to be heard by the listener.

The audio player 22 starts playing audio in response to a playback start signal or button operation (not shown), and outputs an analog or digital target sound signal to the audio amplifier 24.

The audio amplifier 24 amplifies the target sound signal supplied from the audio player 22 and drives the array speaker 26 based on the amplified target sound signal to emit the target sound.

For example, array speaker 25 and array speaker 26 each consist of 16 speakers (speaker units) arranged at equal intervals in the horizontal direction.

Here, array speaker 25-1 and array speaker 25-2 are arranged adjacent to each other at different ends of array speaker 26, i.e., the left and right ends.

Furthermore, the speakers constituting array speaker 25 and array speaker 26 are arranged in a straight line, i.e., at equal intervals in the horizontal direction. Therefore, in this example, 16 x 3 speakers are arranged in a straight line at equal intervals.

Here, an example is described in which an array speaker 26 consisting of multiple speakers is used as a speaker for emitting the target sound, but only one speaker may be used to emit the target sound.

Similarly, an example in which an array speaker 25 is used as a speaker that emits concealment sound is described here, but only one speaker may be used to emit the concealment sound. However, in such a case, it is preferable to emit the concealment sound using a directional speaker so that the concealment sound has the desired directionality.

Furthermore, some speakers on the array speaker 26 side of the array speaker 25 may be used to emit not only the target sound but also the concealed sound. Similarly, some speakers on the array speaker 25 side of the array speaker 26 may be used to emit not only the target sound but also the concealed sound.

Next, referring to Figure 2, we will explain sound leakage that occurs when line array speakers or the like are used as the array speakers 25 and 26. Note that in Figure 2, parts that correspond to those in Figure 1 are given the same reference numerals, and their explanation will be omitted as appropriate.

In the example of Figure 2, for example, concealed sound A is emitted from array speaker 25-1, audio such as an explanation of the advertisement to be displayed, i.e., the target sound, is emitted from array speaker 26, and concealed sound B is emitted from array speaker 25-2.

Furthermore, when sound is emitted from array speaker 25-1, the area where the sound is most audible due to the directionality of the sound, i.e., the area where the sound pressure level is high, is defined as area R11.

In other words, array speaker 25-1 outputs directional concealment sound A so that the concealment sound A can essentially only be heard within area R11.

Here, the output (sound emission) of directional concealment sound A is achieved, for example, by forming directionality using a line array speaker or a directional speaker as array speaker 25-1, or by wave field synthesis, which synthesizes the wave fields of sound from each speaker that makes up array speaker 25-1.

In addition, when sound is emitted from array speaker 26, the area in which the sound can be best heard due to the directivity of the sound is designated as area R12, and when sound is emitted from array speaker 25-2, the area in which the sound can be best heard due to the directivity of the sound is designated as area R13.

That is, for example, the array speaker 26 outputs a directional target sound so that the target sound can basically only be heard within the region R12.

For example, the emission of a directional target sound may be achieved by forming a directivity using a line array speaker or a directional speaker as the array speaker 26, or by wave field synthesis. Note that the target sound does not necessarily have to be directional.

Similarly to the case of array speaker 25-1, array speaker 25-2 also emits directional concealment sound B. In this case, it is possible to impart directionality to concealment sound B by forming directionality using a line array speaker or a directional speaker as array speaker 25-2, or by wave field synthesis.

As described above, the target sound emitted from the array speaker 26 leaks into the regions R11 and R13 at the left and right ends of the array speaker 26, i.e., near the border between region R12 and region R11, and near the border between region R12 and region R13. In other words, sound leakage occurs.

The target sound that leaks out in this way is heard overlapping with the concealed sound A emitted by the array speaker 25-1, for example in area R11.

When a listener hears these overlapping sounds, the influence of masking sound A makes it difficult for the listener to notice (perceive) the leakage of the target sound, i.e., the diffusion of the target sound.

For example, a characteristic of the human ear known as the auditory masking effect occurs when overlapping masking sounds create auditory masking, making it difficult to notice sound leakage.

Furthermore, the auditory masking effect can be enhanced by performing a frequency analysis of the target sound, equalizing the frequency of concealment sound A and emitting it so as to hide (mask) the frequency peak based on the principle of auditory masking.

In addition, by subjecting the target sound to frequency analysis and superimposing a sound that destroys its characteristics onto the concealment sound A, the leaking target sound can be made unclear, making it difficult for the listener to notice the leaking target sound.

Here, destroying the characteristics of the target sound means that when the target sound and a sound that destroys the characteristics of the target sound are played simultaneously, the target sound sounds unclear, in other words, is difficult to hear as meaningful sound. In other words, a sound that destroys the characteristics of the target sound is a sound that has frequency characteristics that cancel out the characteristics of the target sound.

Therefore, for example, a sound that destroys the characteristics of the target sound should be generated such that the frequency components of the downward peaks (valleys) in the frequency waveform (spectrum) of the target sound are large, and when the target sound is synthesized, the frequency waveform of the synthesized sound is roughly flat.

Methods of generating speech that destroy the characteristics of certain speech are described in detail, for example, in "Akagi Masato, Irie Yoshihiro, 'Privacy protection for speech based on concepts of auditory scene analysis' Technical Research Report of the Institute of Electronics, Information and Communication Engineers. EA, Applied Acoustics 111(333), 19-24, 2011-12-02."

Note that, in the above, we have explained the relationship between the target sound emitted toward area R12 and the concealed sound A emitted toward area R11, but the same can be said about the relationship between the target sound emitted toward area R12 and the concealed sound B emitted toward area R13.

Next, we will explain the sound leakage of concealed sound A emitted into area R11 by array speaker 25-1.

Similar to the aforementioned leakage of the target sound into area R11, the concealed sound A leaks to the right of area R11 in the figure. This leaked sound can be heard in area R14, adjacent to the right side of area R11.

In such a case, in area R14 adjacent to the right of area R11, the actual environmental sound heard in area R14 will overlap with the leaked concealed sound A. In this case, if the concealed sound A has similar characteristics to the actual environmental sound in area R14, the listener will find it difficult to notice the leak of concealed sound A.

The actual environmental sound heard in area R14 is not the sound emitted by the array speaker 25-1, but the sound emitted from one or more sound sources actually existing around area R14. Here, the actual environmental sound heard in area R14 is also referred to as environmental sound C.

Here, in order to make the concealed sound A and the actual environmental sound C in area R14 have similar characteristics, for example, the sound observed in area R14 can be recorded (collected) in advance, and the resulting sound (environmental sound C) can be emitted from array speaker 25-1 as concealed sound A.

Note that while we have explained here the sound leakage of concealed sound A emitted toward area R11, the same can be said for concealed sound B emitted toward area R13.

In other words, by collecting actual environmental sounds in area R15 adjacent to the left side of area R13 in the diagram and emitting the collected sounds as concealment sound B from array speaker 25-2, it becomes difficult to notice the leakage of concealment sound B in area R15.

Also, here, an example has been described in which the concealment sound is emitted in the horizontal direction of the region R12 from which the target sound is emitted, i.e., toward the adjacent regions R11 and R13 on both the left and right sides. However, this is not limiting, and the concealment sound may be emitted in the vertical direction of the region R12, i.e., toward adjacent regions above or below.

<Explanation of Regeneration Treatment>
Next, the reproduction process performed by the sound emitting system 11 will be described with reference to the flowchart of FIG.

In step S11, the audio player 21 outputs a pre-stored concealment sound signal to the audio amplifier 23.

Here, the concealment sound signal output from the audio player 21 may be, for example, an audio signal obtained by collecting environmental sound in advance in an area adjacent to the area from which the array speaker 25 emits sound, on the opposite side to the array speaker 26, or may be obtained by further applying equalization processing or the like to the audio signal.

The equalizing process here refers to a process of adjusting the magnitude of each frequency component of the concealment sound so that, for example, the frequency components that are peaks in the frequency waveform of the target sound are masked. The concealment sound signal may also be an audio signal of an environmental sound, or a signal obtained by performing an equalization process on that audio signal, plus an audio signal of a sound that destroys the characteristics of the target sound.

Alternatively, the concealed sound signal may be an audio signal of environmental sound, or a signal that has been subjected to equalization processing to mask the target sound from that audio signal, and then further subjected to equalization processing that adds frequency characteristics that destroy the characteristics of the target sound.

In step S12, the audio player 22 outputs the target sound signal stored in advance to the audio amplifier 24.

In step S13, audio amplifier 23 and audio amplifier 24 amplify the concealment sound signal supplied from audio reproducer 21 and the target sound signal supplied from audio reproducer 22, and supply them to array speaker 25 and array speaker 26.

In step S14, the array speaker 25 and the array speaker 26 output (emit) sounds based on the concealment sound signal and the target sound signal supplied from the audio amplifier 23 and the audio amplifier 24. As a result, the concealment sound is reproduced by the array speaker 25, and the target sound is reproduced by the array speaker 26.

Once the concealed sound and target sound have been played in this manner, the playback process ends.

In this way, the sound emission system 11 emits not only the target sound but also the concealed sound. In this way, it is possible to make it difficult to hear sounds leaking outside the specified direction.

For example, in the example described with reference to Figure 2, by emitting concealment sound A and concealment sound B based on the concealment sound signal obtained by performing the above-mentioned equalizing process, it is possible to make it difficult to perceive leakage of the target sound in areas R11 and R13 outside the specified direction of the target sound, i.e., in a direction different from the desired direction.

In addition, by emitting concealed sound A and concealed sound B based on a concealed sound signal obtained from a signal obtained by actually picking up environmental sound, not only can sound leakage be less perceptible in areas R14 and R15, but it can also be made to sound as if only actual environmental sound is being heard in areas R11 and R13.

Second Embodiment
<Example of sound projection system configuration>
(Sound is picked up by a microphone and then released as concealed sound)
Moreover, the sound output system to which the present technology is applied may be configured as shown in Fig. 4. In Fig. 4, the same reference numerals are given to the parts corresponding to those in Fig. 1, and the description thereof will be omitted as appropriate.

The sound output system 51 shown in Figure 4 has a microphone 61-1, a microphone 61-2, a microphone processing device 62-1, a microphone processing device 62-2, an audio player 22, an audio amplifier 23-1, an audio amplifier 23-2, an audio amplifier 24, an array speaker 25-1, an array speaker 25-2, and an array speaker 26.

The configuration of the sound output system 51 shown in Figure 4 differs from that of the sound output system 11 in that microphones 61-1 and 61-2 are newly provided, and microphone processing devices 62-1 and 62-2 are provided instead of the audio player 21, but in other respects it has the same configuration as the sound output system 11.

The microphone 61-1 is positioned on the right side as viewed by a listener looking at the array speaker 25-1 from the front, i.e., at a predetermined distance away from the array speaker 25-1 on the opposite side from the array speaker 26.

For example, the microphone 61-1 picks up the surrounding environmental sound in real time when the target sound is emitted, and supplies the resulting environmental sound signal to the microphone processing device 62-1. Note that the pickup of the environmental sound by the microphone 61-1 does not necessarily have to be performed in real time.

The microphone processing device 62-1 converts the environmental sound signal supplied from the microphone 61-1 from an analog signal to a digital signal by A/D (Analog/Digital) conversion, and supplies the resulting digital signal to the audio amplifier 23-1 as a concealment sound signal.

The audio amplifier 23-1 amplifies the concealment sound signal supplied from the microphone processing device 62-1 and drives the array speaker 25-1 to emit sound based on the amplified concealment sound signal.

Similarly, microphone 61-2 is positioned on the left side of array speaker 25-2 as viewed from the front by a listener, i.e., a predetermined distance away from array speaker 25-2 on the opposite side from array speaker 26.

For example, the microphone 61-2 picks up the surrounding environmental sound in real time when the target sound is emitted, and supplies the resulting environmental sound signal to the microphone processing device 62-2. Note that the pickup of the environmental sound by the microphone 61-2 does not necessarily have to be performed in real time.

The microphone processing device 62-2 converts the environmental sound signal supplied from the microphone 61-2 from an analog signal to a digital signal by A/D conversion, and supplies the resulting digital signal to the audio amplifier 23-2 as a concealment sound signal.

The audio amplifier 23-2 amplifies the concealment sound signal supplied from the microphone processing device 62-2 and drives the array speaker 25-2 to emit sound based on the amplified concealment sound signal.

In the following, when there is no need to distinguish between microphone 61-1 and microphone 61-2, they will be referred to simply as microphone 61.In the following, when there is no need to distinguish between microphone processing device 62-1 and microphone processing device 62-2, they will be referred to simply as microphone processing device 62.

In the sound output system 51, as in the sound output system 11, the speakers constituting the array speaker 25 and the array speaker 26 are arranged in a straight line, that is, at equal intervals in the horizontal direction. Therefore, in this example, 16 x 3 speakers are arranged at equal intervals.

Next, referring to Figure 5, we will explain sound leakage that occurs when line array speakers or the like are used as the array speakers 25 and 26. Note that in Figure 5, parts that correspond to those in Figure 2 or Figure 4 are given the same reference numerals, and their explanation will be omitted as appropriate.

In the example of Figure 5, concealed sound A obtained by collecting environmental sound with microphone 61-1 is emitted from array speaker 25-1, and concealed sound B obtained by collecting environmental sound with microphone 61-2 is emitted from array speaker 25-2.

Here, microphones 61-1 and 61-2 are positioned within areas R14 and R15, respectively, i.e., in the vicinity of areas R11 and R13 where concealed sounds are emitted.

In addition, the array speaker 26 emits audio, such as an explanation of the advertisements being displayed, i.e., the target sound.

Furthermore, as in the example in Figure 2, the area in which the concealed sound A emitted by the array speaker 25-1 is best heard is area R11, the area in which the target sound is best heard is area R12, and the area in which the concealed sound B emitted by the array speaker 25-2 is best heard is area R13.

As described above, the target sound emitted by the array speaker 26 leaks out in directions outside the specified direction, i.e., toward area R11 or area R13, near the boundary between areas R11 and R12, and near the boundary between areas R12 and R13.

In this way, the target sound that leaks out is heard overlapping with the concealment sound A emitted by the array speaker 25-1, for example in area R11. When a listener hears these overlapping sounds, the influence of the concealment sound A makes it difficult for the listener to notice (perceive) the leakage of the target sound.

For example, auditory masking occurs due to the influence of overlapping concealing sound A, a characteristic of the human ear known as the auditory masking effect, making it difficult to notice sound leakage.

Furthermore, the auditory masking effect can be enhanced by performing frequency analysis on the target sound and emitting the concealment sound A with equalized frequency so as to hide (mask) the frequency peak based on the principle of auditory masking.

In addition, by subjecting the target sound to frequency analysis and superimposing a sound that destroys its characteristics onto the concealment sound A, the leaking target sound can be made unclear, making it difficult for the listener to notice the leaking target sound.

Note that, in the above, we have explained the relationship between the target sound emitted toward area R12 and the concealed sound A emitted toward area R11, but the same can be said about the relationship between the target sound emitted toward area R12 and the concealed sound B emitted toward area R13.

Next, we will explain the sound leakage of concealed sound A emitted into area R11 by array speaker 25-1.

Similar to the aforementioned leakage of the target sound into area R11, the concealed sound A leaks to the right of area R11 in the figure. This leaked sound can be heard in area R14, adjacent to the right side of area R11.

In such a case, in area R14, the actual environmental sound C heard in area R14 and the concealed sound A that has leaked out will be heard overlapping.

In this case, if the concealed sound A has similar characteristics to the actual environmental sound C in area R14, the listener will find it difficult to notice the leakage of the concealed sound A.

In this example, concealed sound A is obtained by collecting actual environmental sound C with microphone 61-1. Therefore, the concealed sound A heard by a listener in area R14 is observed and heard in approximately the same location as the actual environmental sound that overlaps with the concealed sound A, making it difficult to notice sound leakage.

Note that while we have explained here the sound leakage of concealed sound A emitted toward area R11, the same can be said for concealed sound B emitted toward area R13.

In the sound emission system 51 described above, the playback process is basically as described with reference to Figure 3, but in the process corresponding to step S11, a concealed sound signal obtained from the environmental sound signal picked up by the microphone 61 is output to the audio amplifier 23.

<Modification 1 of the second embodiment>
<Example of sound projection system configuration>
(When there are multiple microphones)
In addition, in the sound emission system 51 shown in Figure 4, an example has been described in which one microphone 61 is placed in an area adjacent to the area where the concealed sound is emitted by the array speaker 25, but this is not limited to the above, and multiple microphones may be placed.

For example, in the example shown in Figure 5, microphone 61 is used to pick up actual environmental sounds in the location (area) from which concealed sounds A and B emitted from the array speaker 25 leak out, and areas R14 and R15 where sound leakage occurs are areas of a certain range.

Therefore, the actual environmental sounds heard in these areas R14 and R15 are not exactly the same depending on the listening position. Therefore, by collecting the environmental sounds at each of these positions (locations) and mixing them, it is possible to obtain the average environmental sounds in the entire area R14 or the entire area R15 where sound leakage occurs as concealment sounds.

In such a case, the sound emission system is configured, for example, as shown in Figure 6. Note that in Figure 6, parts corresponding to those in Figure 4 are given the same reference numerals, and their explanation will be omitted as appropriate.

The sound output system 91 shown in Figure 6 has microphones 101-1 to 101-6, microphone processing devices 62-1, microphone processing devices 62-2, audio player 22, audio amplifiers 23-1, audio amplifiers 23-2, audio amplifiers 24, array speaker 25-1, array speaker 25-2, and array speaker 26.

The configuration of sound emission system 91 differs from that of sound emission system 51 in that microphones 101-1 to 101-6 are provided instead of microphone 61, but in other respects it has the same configuration as sound emission system 51.

Microphones 101-1 to 101-3 are positioned on the right side of the array speaker 25-1 as viewed from the front by a listener, i.e., at a predetermined distance away from the array speaker 25-1 on the opposite side from the array speaker 26.

Microphones 101-1 to 101-3 pick up surrounding environmental sounds and supply the resulting environmental sound signals to the microphone processing device 62-1.

The microphone processing device 62-1 A/D converts and mixes the environmental sound signals supplied from microphones 101-1 to 101-3 to generate a final concealed sound signal, which it supplies to the audio amplifier 23-1.

Microphones 101-4 to 101-6 are positioned on the left side of the array speaker 25-2 as viewed from the front by a listener, i.e., at a predetermined distance away from the array speaker 25-2 on the opposite side from the array speaker 26.

Microphones 101-4 to 101-6 pick up surrounding environmental sounds and supply the resulting environmental sound signals to the microphone processing device 62-2.

The microphone processing device 62-2 A/D converts and mixes the environmental sound signals supplied from microphones 101-4 to 101-6 to generate a final concealed sound signal, which it supplies to the audio amplifier 23-2.

In the following, when there is no need to distinguish between microphones 101-1 to 101-6, they will simply be referred to as microphones 101.

Figure 7 shows an example of the arrangement of microphones 101. Note that in Figure 7, parts corresponding to those in Figure 5 are given the same reference numerals, and their explanation will be omitted as appropriate.

In the example shown in Figure 7, similar to the case shown in Figure 5, the speakers constituting the array speaker 25 and the array speaker 26 are arranged in a straight line, i.e., at equal intervals in the horizontal direction. Therefore, in this example, 16 x 3 speakers are arranged at equal intervals.

In addition, three microphones 101-1 to 101-3 are positioned at intervals within area R14, and similarly, three microphones 101-4 to 101-6 are positioned at intervals within area R15.

For example, by collecting actual environmental sounds using three microphones 101 arranged at positions distant from each other in area R14 and mixing the resulting environmental sound signals, it is possible to obtain a concealed sound signal for the average environmental noise that would be heard in area R14. The same can be said for area R15 as for area R14.

<Explanation of Regeneration Treatment>
Next, a description will be given of the operation of the sound emitting system 91. That is, hereinafter, a reproduction process performed by the sound emitting system 91 will be described with reference to the flowchart of FIG.

When the playback process begins, each microphone 101 begins picking up the surrounding environmental sounds and supplies the resulting environmental sound signal to the microphone processing device 62.

In particular, here, the environmental sound signals obtained by microphones 101-1 to 101-3 are supplied to microphone processing device 62-1, and the environmental sound signals obtained by microphones 101-4 to 101-6 are supplied to microphone processing device 62-2.

In step S41, the microphone processing device 62 converts each environmental sound signal supplied from each microphone 101 from an analog signal to a digital signal by A/D conversion.

In step S42, the microphone processing device 62 performs mixing, i.e., addition processing, based on each A/D converted environmental sound signal to generate a concealment sound signal.

For example, in the microphone processing device 62-1, the environmental sound signals supplied from microphones 101-1 to 101-3 and A/D converted are added together to form a single concealed sound signal.

When mixing environmental sound signals, a weight corresponding to the position of each microphone 101 may be used to perform weighted addition of the environmental sound signals picked up by each microphone 101, i.e., mixing them in a certain ratio, to generate a concealment sound signal.

In step S43, the microphone processing device 62 outputs the digital concealment sound signal obtained by mixing to the audio amplifier 23.

In step S44, the audio player 22 outputs the target sound signal stored in advance to the audio amplifier 24.

For example, the audio player 22 stores a target sound signal, which is an audio signal of a target sound such as a description of an advertisement to be displayed that has been recorded in advance. The audio player 22 outputs the digital target sound signal to the audio amplifier 24 in response to a playback start signal or a button operation (not shown).

In step S45, the audio amplifier 23 and the audio amplifier 24 amplify the concealment sound signal supplied from the microphone processing device 62 and the target sound signal supplied from the audio player 22, and supply them to the array speaker 25 and the array speaker 26.

In step S46, the array speaker 25 and the array speaker 26 output (emit) sounds based on the concealment sound signal and the target sound signal supplied from the audio amplifier 23 and the audio amplifier 24. As a result, the concealment sound is reproduced by the array speaker 25, and the target sound is reproduced by the array speaker 26.

Once the concealed sound and target sound have been played in this manner, the playback process ends.

In this way, the sound emission system 91 emits not only the target sound but also the concealed sound. In this way, it is possible to make it difficult to hear sounds leaking outside the specified direction. In particular, the sound emission system 91 can record averaged environmental noise by mixing environmental sound signals obtained by microphones 101 placed in multiple different positions, making it possible to make sound leakage less noticeable.

<Modification 2 of the second embodiment>
<Example of sound projection system configuration>
(When selecting from multiple pre-stored concealment signals)
Incidentally, in the sound emission system 51 shown in FIG. 4, the microphone processing device 62-1 and the microphone processing device 62-2 may store concealment sound signals of a plurality of different concealment sounds obtained by recording a plurality of environmental sounds in advance.

In this case, for example, the microphone processing device 62 selects from among a number of concealed sound signals stored in advance, one to be output to the audio amplifier 23 based on the environmental sound signal obtained by the microphone 61.

For example, if the sound emission system 51 is installed in a train station corridor, the environmental sounds at the installation location are likely to change over time.

Specifically, for example, the characteristics of environmental sounds during the rush hour in the morning and the quieter hours in the afternoon (ambient noise) are different.

For this reason, multiple environmental sounds at different times or days of the week, i.e., sounds with different collection timing, can be recorded (collected) in advance, and the signals of these environmental sounds can be stored as concealment sound signals in each microphone processing device 62.

At this time, a frequency analysis is performed in advance on each concealment sound signal, and the resulting feature data is associated with the concealment sound signal and stored in the microphone processing device 62. This feature data may be any data that indicates frequency-related characteristics, such as the frequency characteristics of the concealment sound signal.

In this way, when a plurality of pre-recorded concealment sound signals and feature data are associated and stored, the sound emission system 51 performs the playback process shown in Fig. 9. That is, the playback process performed by the sound emission system 51 will be described below with reference to the flowchart in Fig. 9.

When the playback process begins, each microphone 61 begins picking up the surrounding environmental sounds and supplies the resulting environmental sound signal to the microphone processing device 62.

In step S71, the microphone processing device 62 performs A/D conversion on the environmental sound signal supplied from the microphone 61, thereby converting the analog signal into a digital signal.

In step S72, the microphone processing device 62 accumulates the environmental sound signal for a predetermined period of time obtained in step S71, and performs frequency analysis on the accumulated environmental sound signal to generate feature data.

In step S73, the microphone processing device 62 compares the feature data obtained in step S72 with a plurality of feature data stored in advance, and selects, from the plurality of feature data, the feature data that is closest to the feature data obtained in step S72. The microphone processing device 62 also selects the concealment sound signal that is associated with the feature data selected in this manner.

Here, the closest feature data refers to, for example, the feature data with the smallest difference between them or the feature data with the shortest distance between them.

The concealment sound signal selected in this manner is the one, among the pre-stored concealment sound signals, that is, the one that is closest (similar) to the actual environmental sound signal, i.e., the one that has the most similar characteristics.

In step S74, the microphone processing device 62 outputs the concealment sound signal stored in correspondence with the feature data selected in step S73 to the audio amplifier 23.

Once the concealment sound signal has been output in this manner, steps S75 to S77 are then performed and the playback process is terminated. However, as these steps are similar to steps S44 to S46 in FIG. 8, their description will be omitted.

In this manner, the sound emission system 51 selects from among a number of concealment sound signals prepared in advance one that is closest to the environmental sound signal actually picked up by the microphone 61, and emits the concealment sound based on the selected concealment sound signal.

In this way, it is possible to emit not only the target sound but also the concealed sound, making it difficult to hear sounds leaking out of the specified direction. In particular, it is possible to emit concealed sounds with characteristics similar to actual environmental sounds, further improving the effect of making leaking sounds difficult to hear.

Moreover, by emitting concealment sounds that have characteristics similar to actual environmental sounds, it is also possible to suppress the audio loop (howling) described below.

<Modification 3 of the second embodiment>
<Howling Suppression>
In the sound emission system 51 shown in FIG. 4, the surrounding environmental sound is picked up by the microphone 61, and the resulting environmental sound signal is A/D converted by the microphone processing device 62 to a digital concealed sound signal.

Then, the concealment sound signal is amplified by the audio amplifier 23 and supplied to the array speaker 25, and the concealment sound is emitted from the array speaker 25.

At this time, depending on the position of the microphone 61, the concealed sound emitted from the array speaker 25 may be picked up again by the microphone 61. Similarly, the target sound emitted from the array speaker 26 may also be picked up by the microphone 61. This causes an audio loop and, in some cases, may cause a howling phenomenon.

Therefore, in order to suppress such howling, the microphone 61 may be placed at a position away from the area where sound is emitted with directionality from the array speaker 25, i.e., area R11 or area R13 in Figure 5 described above.

Specifically, for example, when collecting sound using microphone 61, microphone 61 can be positioned at a position such that the components (sound pressure level) of the target sound and concealed sound contained in the environmental sound signal obtained by the sound collection are below a predetermined value (predetermined level).

Another method for suppressing audio loops (howling) is to use a directional microphone as microphone 61, thereby selectively preventing sounds emitted from array speaker 25 and array speaker 26 from being picked up by microphone 61.

For example, one such method would be to orient the acutely directional microphone so that microphone 61 does not pick up concealed sounds or sounds from the direction in which the target sound is coming.

In other words, in this example, microphone 61 is positioned so that the direction in which the sound pickup sensitivity of microphone 61 is lower than other directions (the direction of null directivity) faces the direction from which the concealed sound or the target sound is coming.

Alternatively, for example, microphone beamforming technology may be used to orient the null directivity of the microphone 61 toward the array speaker 25, so that the microphone 61 does not pick up the concealed sound or the target sound. In this case, beamforming is performed on the environmental sound signal in the microphone processing device 62.

In addition to beamforming, the microphone processing device 62 may apply any filter processing to the environmental sound signal to suppress audio loops (howling) to generate a concealment sound signal.

For example, in the microphone processing device 62, a delay process may be performed to delay the environmental sound signal obtained by the microphone 61 by a predetermined time, i.e., by adding a delay to the environmental sound signal to make it a concealed sound signal, thereby suppressing audio loops (howling).

In addition, the microphone processing device 62 may perform notch filter processing on the frequency amplified by the audio loop on the environmental sound signal obtained by the microphone 61, and use the resulting signal as a concealment sound signal to suppress the audio loop (howling). This reduces the frequency components at which the audio loop occurs.

Furthermore, in the microphone processing device 62, gain correction is performed on the environmental sound signal obtained by the microphone 61 by applying a predetermined gain that attenuates the audio loop, and the resulting signal is treated as a concealment sound signal, thereby suppressing the audio loop (howling).

In addition, multiple methods for suppressing audio loops, such as the placement of microphone 61 and filter processing described above, may be combined.

<Fourth Modification of the Second Embodiment>
<Regarding frequency characteristic correction>
(Correcting the characteristics of the array speaker and microphone to make the concealed sound closer to the ambient sound)
Also, in the sound emission system 51 shown in FIG. 4, the surrounding environmental sound is picked up by the microphone 61, and the resulting environmental sound signal is A/D converted by the microphone processing device 62 to a digital concealed sound signal.

Then, the concealment sound signal is amplified by the audio amplifier 23 and supplied to the array speaker 25, and the concealment sound is emitted from the array speaker 25.

During the process of emitting such concealed sound, the array speaker 25 emits sound with frequency characteristics that depend on the characteristics of the microphone 61 and the array speaker 25.

For example, assume that the array speaker 25 has the frequency characteristic shown by the arrow Q11 in Figure 10. In Figure 10, the horizontal axis indicates frequency, and the vertical axis indicates the level of each frequency component.

In the example shown by arrow Q11 in Figure 10, the frequency characteristics are such that the mid-high range is boosted. When using an array speaker 25 with such frequency characteristics, an equalization process may be performed on the concealment sound signal using an audio equalizer to correct the frequency characteristics so that the frequency characteristics of the array speaker 25 after correction become the flat characteristics shown by arrow Q12.

For example, assume that microphone 61 has the frequency characteristic shown by arrow Q21 in Figure 11. In Figure 11, the horizontal axis indicates frequency, and the vertical axis indicates the level of each frequency component.

In the example shown by arrow Q21 in Figure 11, the frequency characteristics are such that the high frequencies are boosted. When using a microphone 61 with such frequency characteristics, an equalization process may be performed on the environmental sound signal using an audio equalizer to correct the frequency characteristics so that the frequency characteristics of the microphone 61 after correction become the flat characteristics shown by arrow Q22. Such equalization process can be achieved, for example, by filtering using a single filter or filtering using a combination of multiple filters.

When the sound picked up by the microphone 61 is emitted from the array speaker 25 as concealed sound, if the frequency characteristics of the microphone 61 and the array speaker 25 are flat, the characteristics of the concealed sound will become closer to the characteristics of the original environmental sound during the process from sound collection to sound emission.

Therefore, in the microphone processing device 62, an equalization process is performed on the environmental sound signal using an audio equalizer to correct the frequency characteristics, and the resulting signal is used as a concealment sound signal, making it possible to output a sound that is closer to the environmental sound as the concealment sound.

In other words, for example, an audio equalizer can be used to perform equalization processing on the environmental sound signal obtained by microphone 61 so that the environmental sound signal has the flat characteristics shown by arrow Q22 in Figure 11, and the resulting signal can be used as a concealment sound signal.

Furthermore, an equalization process can be performed on the concealment sound signal by an audio equalizer so that the emitted concealment sound has the flat characteristics shown by the arrow Q12 in Fig. 10. Alternatively, an equalization process can be performed on the environmental sound signal (concealment sound signal) to add only one of the frequency characteristics shown by the arrow Q12 in Fig. 10 and the frequency characteristics shown by the arrow Q22 in Fig. 11.

In this way, by using an audio equalizer to raise or suppress the levels of specific frequency bands, such as the mid-high and high frequencies, in order to achieve a flat frequency response, it is possible to emit concealed sounds that are closer to the original ambient sound.

Note that although the above describes a method of correcting frequency characteristics using an audio equalizer, the method is not limited to this and frequency characteristics may be corrected using any other method.

For example, the impulse response may be measured in advance, a filter with the inverse characteristics of the impulse response may be calculated, and the environmental sound signal or the concealed sound signal may be filtered using the obtained filter. This prior measurement of the impulse response may be performed for each of the microphone 61 and the array speaker 25, or may be performed for the entire system of the microphone 61 and the array speaker 25.

Therefore, for example, a filter process using a synthesis filter of a filter that adds the inverse characteristic of the frequency characteristic shown by arrow Q11 in Figure 10 and a filter that adds the inverse characteristic of the frequency characteristic shown by arrow Q21 in Figure 11 can be performed as an equalization process on the environmental sound signal, and the resulting signal can be used as a concealment sound signal.

In addition, filtering using either a filter that adds the inverse of the frequency characteristics shown by arrow Q11 in Figure 10, or a filter that adds the inverse of the frequency characteristics shown by arrow Q21 in Figure 11, may be performed as equalizing processing on the environmental sound signal.

Furthermore, even when suppressing audio loops or making the concealment sound closer to environmental sounds as described above, the concealment sound may also have frequency characteristics that cancel out the characteristics of the target sound.

In such cases, the concealment sound signal can be subjected to an equalization process that adds frequency characteristics that cancel out the characteristics of the target sound, or an audio signal having frequency characteristics that cancel out the characteristics of the target sound can be added to the concealment sound signal to produce the final concealment sound signal.

Third embodiment
Concealed sounds and target sounds
Furthermore, in the above, it has been explained that in the sound output system 11, the sound output system 51, and the sound output system 91, a total of three array speakers consisting of two array speakers 25 and one array speaker 26 are arranged in a row (straight line).

In particular, an example was described in which one target sound is emitted from the array speaker 26 located in the center of the three array speakers, and concealment sounds are emitted from each array speaker 15 located to the left and right of the array speaker 26.

However, in a sound emission system to which this technology is applied, the number of target sounds is not limited to one, and multiple target sounds may be emitted simultaneously.

Specifically, for example, five array speakers are arranged in a row (straight line). In this case, when the array speakers are viewed from the front, concealment sound 1, target sound 1, concealment sound 2, target sound 2, and concealment sound 3 may be emitted in that order from the left array speaker to the right array speaker.

As described above, according to this technology, even if a directional speaker is used and the target sound diffuses, the diffusion (sound leakage) of the target sound and the concealment sound can be made less noticeable by emitting the concealment sound toward an area adjacent to the area where the target sound is emitted. In other words, it is possible to make it difficult to hear the sound leaking outside the specified direction.

In particular, by using a microphone to pick up actual environmental sounds in the area from which concealed sounds leak out and using them as concealed sounds, sounds leaking outside the specified direction can be made even more difficult to hear.

In addition, by selecting an appropriate signal from among multiple concealment sound signals and performing gain correction on the concealment sound signal, it is possible to suppress audio loops (howling). Furthermore, by correcting the frequency characteristics of the array speaker and microphone, it is possible to make the characteristics of the concealment sound closer to those of the actual environmental sound.

Example of computer configuration
The above-mentioned series of processes can be executed by hardware or software. When the series of processes is executed by software, the program constituting the software is installed in a computer. Here, the computer includes a computer built into dedicated hardware, and a general-purpose personal computer, for example, capable of executing various functions by installing various programs.

Figure 12 is a block diagram showing an example of the hardware configuration of a computer that executes the above-mentioned series of processes using a program.

In the computer, a CPU (Central Processing Unit) 501, a ROM (Read Only Memory) 502, and a RAM (Random Access Memory) 503 are interconnected by a bus 504.

An input/output interface 505 is further connected to the bus 504. An input unit 506, an output unit 507, a recording unit 508, a communication unit 509, and a drive 510 are connected to the input/output interface 505.

The input unit 506 includes a keyboard, a mouse, a microphone, an image sensor, etc. The output unit 507 includes a display, a speaker, etc. The recording unit 508 includes a hard disk, a non-volatile memory, etc. The communication unit 509 includes a network interface, etc. The drive 510 drives a removable recording medium 511 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory.

In a computer configured as described above, the CPU 501 performs the above-mentioned series of processes, for example, by loading a program recorded in the recording unit 508 into the RAM 503 via the input/output interface 505 and the bus 504 and executing it.

The program executed by the computer (CPU 501) can be provided, for example, by recording it on a removable recording medium 511 such as a package medium. The program can also be provided via a wired or wireless transmission medium such as a local area network, the Internet, or digital satellite broadcasting.

In a computer, a program can be installed in the recording unit 508 via the input/output interface 505 by mounting the removable recording medium 511 in the drive 510. The program can also be received by the communication unit 509 via a wired or wireless transmission medium and installed in the recording unit 508. Alternatively, the program can be pre-installed in the ROM 502 or the recording unit 508.

The program executed by the computer may be a program in which processing is performed chronologically in the order described in this specification, or a program in which processing is performed in parallel or at the required timing, such as when called.

Furthermore, the embodiments of the present technology are not limited to the above-described embodiments, and various modifications are possible without departing from the spirit and scope of the present technology.

For example, this technology can be configured as cloud computing, in which a single function is shared and processed collaboratively by multiple devices over a network.

In addition, each step described in the above flowchart can be executed by a single device, or can be shared and executed by multiple devices.

Furthermore, when a single step includes multiple processes, the multiple processes included in that single step can be executed by a single device or can be shared and executed by multiple devices.

Furthermore, this technology can also be configured as follows.

(1)
one or more first speakers that emit a target sound;
and one or more second speakers arranged adjacent to the one or more first speakers and configured to emit directional concealment sound.
(2)
The sound output system according to (1), wherein the one or more second speakers are arranged adjacent to each of a plurality of ends of the one or more first speakers.
(3)
The sound emission system according to (1) or (2), wherein the concealment sound has a frequency characteristic that cancels out the characteristic of the target sound.
(4)
The one or more second speakers emit the concealment sound based on a concealment sound signal obtained based on a signal of an environmental sound collected in the vicinity of an area where the concealment sound is emitted. The sound emission system described in any one of (1) to (3).
(5)
The sound emission system according to (4), further comprising a plurality of microphones that pick up the environmental sounds.
(6)
The sound output system according to (5), wherein the concealment sound signal is generated by mixing signals obtained by sound pickup by the plurality of microphones in a certain ratio.
(7)
The one or more second speakers emit the concealment sound based on the concealment sound signal selected from among the plurality of concealment sound signals obtained based on each of the plurality of environmental sound signals previously picked up by the microphone at different timings. The sound emission system described in (5) or (6).
(8)
The sound output system according to any one of (4) to (7), wherein the microphone has a directionality that suppresses the emitted target sound or the concealed sound.
(9)
The sound output system according to any one of (4) to (6), wherein the concealment sound signal is a signal obtained by performing a delay process on the environmental sound signal.
(10)
The concealment sound signal is a signal obtained by performing a filter process on the environmental sound signal to suppress an audio loop of the target sound or the concealment sound. The sound emission system according to any one of (4) to (6).
(11)
The concealment sound signal is a signal obtained by performing gain correction on the environmental sound signal to suppress an audio loop of the target sound or the concealment sound. The sound emission system described in any one of (4) to (6).
(12)
The plurality of microphones are arranged at positions where the level of the target sound or the concealed sound contained in the picked-up environmental sound is equal to or lower than a predetermined level. The sound emission system according to any one of (4) to (11).
(13)
The sound output system according to any one of (4) to (6), wherein the concealment sound signal is a signal obtained by performing an equalization process on the environmental sound signal to add a frequency characteristic that cancels out the characteristic of the target sound.
(14)
The sound output system according to any one of (4) to (6), wherein the concealment sound signal is a signal obtained by adding a sound signal having frequency characteristics that cancel out the characteristics of the target sound to the environmental sound signal.
(15)
The concealment sound signal is a signal obtained by applying an equalization process to the environmental sound signal based on at least one of the frequency characteristics of the multiple microphones measured in advance and the frequency characteristics of the one or multiple second speakers.A sound emission system described in any one of (4) to (6).

11 Sound output system, 21-1, 21-2, 21 Audio player, 22 Audio player, 25-1, 25-2, 25 Array speaker, 26 Array speaker, 61-1, 61-2, 61 Microphone, 62-1, 62-2, 62 Microphone processing device, 101-1 to 101-6, 101 Microphone

Claims (5)

one or more first speakers that emit a target sound;
One or more second speakers arranged adjacent to the one or more first speakers and emitting directional concealment sound ;
a plurality of microphones for collecting environmental sounds in the vicinity of an area where the concealed sound is emitted;
Equipped with
The one or more second speakers emit the concealment sound based on the concealment sound signal selected from among a plurality of concealment sound signals obtained based on a plurality of environmental sound signals previously collected by the microphone at different timings, based on the environmental sound signal collected by the microphone.
Sound emission system. The sound output system according to claim 1 , wherein the one or more second speakers are arranged adjacent to each of a plurality of ends of the one or more first speakers. The sound emitting system according to claim 1 , wherein the concealment sound has a frequency characteristic that cancels out a characteristic of the target sound. The microphone has a directivity that suppresses the emitted target sound or the concealed sound.
A sound emission system according to claim 1 . The plurality of microphones are arranged at positions where the level of the target sound or the concealed sound contained in the picked-up environmental sound is equal to or lower than a predetermined level.
A sound emission system according to claim 1 .

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