Patent Description:
<CIT> discloses a technique to adjust the level of sound outputted from a speaker, according to the volume of each talker.

<CIT> discloses a technique to adjust the level of sound outputted from a speaker, according to a surrounding noise amount.

Both of <CIT> and <CIT> relate to a technology to simply adjust the level of sound to be outputted from a speaker. Neither <CIT> nor <CIT> discloses a technology to adjust an audio signal received from a device on a far-end side.

<CIT> discloses a voice amplifying phone for carrying out voice amplification with a proper voice volume in response to the magnitude of surrounding noise and suppressing production of howling at the same time. Since an estimate value of a near end side surrounding noise level is updated when a near end side voice interval detection section detects no voice interval, a voice volume correction amount adjustment means adjusts a correction amount in a voice volume correction means to a proper value in response to a surround noise level so as to attain a voice amplifying speech in a proper voice volume in response to the magnitude of the surrounding noise. Since the voice volume correction amount adjustment means adjusts the correction amount only when the voice interval is detected, production of howling caused by a sneak path from a speaker to a microphone can be suppressed. Further, since no correction amount is adjusted while an adaptive filter of a first echo canceller updates its coefficient, deterioration in the convergence of the adaptive filter can be prevented.

<CIT> discloses a method and a device for controlling a volume to extract human voice from noise when automatically controlling a volume according to noise of a surrounding environment, thereby performing an automatic volume control function considering whether voice noise is mixed. A noise sensor senses external noise. A voice determining unit determines a voice among the external noise. An amplification information storage unit stores amplification information which differentiates an amplification ratio to the output sound caused by the external noise by a frequency band. A sound processor amplifies the output sound according to the amplification control signal.

In view of the foregoing, an object of the present invention is to provide an acoustic device and an acoustic processing method that adjust an audio signal received from a far-end side to an appropriate level.

According to an aspect of the present invention, an acoustic device is provided as set forth in claim <NUM>. According to another aspect of the present invention, an acoustic processing method is provided as set forth in claim <NUM>. Preferred embodiments of the present invention are set forth in the dependent claims.

An acoustic device includes a microphone, a voice feature amount extracting portion that extracts a voice feature amount from sound (corresponding to a first audio signal of the present invention) collected by the microphone, an audio signal receiving portion that receives an audio signal (corresponding to a second audio signal of the present invention) from a different device on a far-end side, and a gain determining portion that determines a gain of the audio signal received from the different device on the far-end side, based on the voice feature amount that has been extracted by the voice feature amount extracting portion.

The voice feature amount includes power level of an audio signal, for example. The acoustic device determines a level of voice of a talker on a far-end side, according to voice of a talker on a near-end side. As an example, the talker on a near-end side talks loudly when a surrounding noise level is high. At this time, when the level of the voice of the talker on a far-end side is low, a user on a near-end side has difficulty hearing the voice of the talker on a far-end side. Therefore, as an example, the acoustic device, when the level of the voice of the talker on a near-end side is high, causes the level of the voice on a far-end side to be high. Accordingly, the acoustic device is able to output the voice received from the far-end side at an appropriate volume.

The acoustic device includes a noise feature amount obtaining portion that obtains a noise feature amount from sound collected by a microphone. The gain determining portion determines a gain, based on a voice feature amount and a noise feature amount.

The noise feature amount includes power level of a noise signal, for example. In such a case, the acoustic device determines the level of the voice of a far-end side, further according to the noise on a near-end side. For example, when the volume of noise is low, even if the level of the voice of the talker on a far-end side is reduced, the user on a near-end side has no difficulty hearing. Therefore, the acoustic device reduces the level of the voice of the talker on a far-end side, when the level of the voice of the talker on a near-end side is high and the level of noise is low.

It is to be noted that the acoustic device includes an echo canceller that removes an echo element from the sound collected by the microphone. The noise feature amount obtaining portion may obtain a noise feature amount from the sound of which the echo element has been removed by the echo canceller.

The acoustic device does not erroneously recognize the voice on a far-end side as noise by removing an echo element. Therefore, the acoustic device is able to obtain a noise feature amount with higher accuracy.

It is to be noted that the acoustic device may include a distinguishing portion that distinguishes a voice section, and the gain determining portion may determine a gain in the voice section that the distinguishing portion has distinguished. The acoustic device, since performing in a limited (in a each of a distinguished) voice section, is able to determine a gain with higher accuracy.

Hereinafter, the acoustic device will be described in more detail. <FIG> is a diagram showing a configuration of an acoustic processing system <NUM>. The acoustic processing system <NUM> includes a plurality (two in <FIG>) of acoustic devices <NUM> and <NUM> that are connected to each other through a network <NUM>.

The acoustic device <NUM> is set at a first point. The acoustic device <NUM> is set at a second point. In other words, the acoustic device <NUM> and the acoustic device <NUM> are set in places remote from each other.

The acoustic device <NUM> and the acoustic device <NUM> are connected to a remote place through the network <NUM>, and are used for a system that performs interactive communication between remote places. For example, the acoustic device <NUM> and the acoustic device <NUM> are used for a conference system in a remote place. The acoustic device <NUM>, for example, sends the voice of a user of the acoustic device <NUM> to a user of the acoustic device <NUM> through the network <NUM>. In addition, the acoustic device <NUM>, for example, sends the voice of the user of the acoustic device <NUM> to the user of the acoustic device <NUM> through the network <NUM>.

In the following description, the user of the acoustic device <NUM> is referred to as a user on a near-end side. In addition, in the following description, the user of the acoustic device <NUM> is referred to as a user on a far-end side.

<FIG> is a block diagram showing a main configuration of the acoustic device <NUM>. It is to be noted that the acoustic device <NUM> has the same configurations and the same functions as the acoustic device <NUM>, so that the description will be omitted.

The acoustic device <NUM> includes a communicating portion <NUM>, a CPU <NUM>, a RAM <NUM>, a memory <NUM>, a microphone <NUM>, a speaker <NUM>, and a user interface (I/F) <NUM>. The communicating portion <NUM> configures the audio signal receiving portion of the present invention.

The CPU <NUM> reads a program from the memory <NUM> being a storage medium and temporarily stores the program in the RAM <NUM>, and thus performs various operations.

The memory <NUM> includes a flash memory or a hard disk drive (HDD). The memory <NUM> stores programs for operating the CPU <NUM> as described above. In addition, the memory <NUM> stores a feature amount extraction program, a gain determination program, an audio signal reception program, and a gain adjusting program. The feature amount extraction program is a program to configure a voice feature amount extracting portion <NUM> to be described below. The gain determination program is a program to configure a gain determining portion <NUM> to be described below. The audio signal reception program is a program to configure an audio signal receiving portion <NUM> to be described below. The gain adjusting program is a program to configure a gain adjusting portion <NUM> to be described below.

The microphone <NUM> obtains surrounding sound as an audio signal. The surrounding sound includes voice of a talker and noise. The microphone <NUM> digitally converts the obtained audio signal. The microphone <NUM> outputs the digitally converted audio signal to the CPU <NUM>.

The CPU <NUM> performs signal processing on the audio signal inputted from the microphone <NUM>. The CPU <NUM> outputs the audio signal on which the signal processing has been performed, to the communicating portion <NUM>. It is to be noted that the acoustic device <NUM> may include a processor (DSP: Digital Signal Processor) exclusively used for the signal processing. In such a case, according to instructions of the CPU <NUM>, the DSP performs signal processing.

The CPU <NUM> outputs the audio signal on which the signal processing has been performed, to the communicating portion <NUM>. The communicating portion <NUM> is connected to the network <NUM>. The communicating portion <NUM> sends the audio signal to the acoustic device <NUM> on a far-end side through the network <NUM>.

In addition, the communicating portion <NUM> receives the audio signal from the acoustic device <NUM> through the network <NUM>. The communicating portion <NUM> outputs the received audio signal to the CPU <NUM>. The CPU <NUM> performs signal processing on the audio signal inputted from the communicating portion <NUM>. The CPU <NUM> outputs the audio signal on which the signal processing has been performed, to the speaker <NUM>.

The speaker <NUM> emits sound based on the audio signal inputted from the CPU <NUM>. It is to be noted that the speaker <NUM>, when receiving an input of a digital signal, emits sound based on the audio signal after performing D/A conversion.

The user I/F <NUM> receives an operation from a user. The operation by the user includes adjustment of the volume of a speaker, for example.

<FIG> is a block diagram showing a functional configuration of the acoustic device <NUM>. The acoustic device <NUM>, as a functional configuration, includes a microphone <NUM>, a voice feature amount extracting portion <NUM>, a gain determining portion <NUM>, an audio signal receiving portion <NUM>, and a gain adjusting portion <NUM>.

The voice feature amount extracting portion <NUM>, the gain determining portion <NUM>, the gain adjusting portion <NUM>, and the audio signal receiving portion <NUM> are implemented by programs of the CPU <NUM>. The audio signal receiving portion <NUM> may be configured by the communicating portion <NUM>.

The voice feature amount extracting portion <NUM> obtains power level of an inputted audio signal. The power level is calculated by the root mean square of an audio signal of a time axis, for example. The power level is an example of the voice feature amount. The extraction of the voice feature amount may be performed by limiting to a predetermined band (such as an FFT band, an octave band, the Mel band, or the Bark band). For example, the voice feature amount extracting portion <NUM> calculates power level of <NUM> to <NUM>. In this manner, the extraction of the voice feature amount may be extracted in a limited band which is a great number of human voice elements. In addition, the extraction of the voice feature amount may be extracted in a plurality of bands.

It is to be noted that the power level of an audio signal is preferably averaged on the time axis. The voice feature amount extracting portion <NUM>, by averaging the power level of an audio signal on the time axis, does not erroneously recognize noise as voice even when high noise sound is suddenly inputted.

The gain determining portion <NUM> determines a gain based on the voice feature amount extracted by the voice feature amount extracting portion <NUM>. <FIG> is a diagram showing the relationship between the voice feature amount and the gain. As shown in <FIG>, the gain determining portion <NUM> sets the gain higher as the power level of an audio signal is higher. The gain determining portion <NUM> sets the gain lower as the power level of an audio signal is lower.

The gain determining portion <NUM> sets the determined gain to the gain adjusting portion <NUM>. The audio signal receiving portion <NUM> receives an audio signal from a device on a far-end side. The gain adjusting portion <NUM> receives an input of an audio signal from the audio signal receiving portion <NUM>, amplifies the audio signal by the set gain, and outputs the amplified audio signal to the speaker <NUM>. In this manner, the gain determining portion <NUM> determines the gain of the audio signal received from a different device on a far-end side, based on the voice feature amount extracted by the voice feature amount extracting portion <NUM>.

Therefore, the acoustic device <NUM>, when the level of voice of a talker on a near-end side is high, causes the level of voice on a far-end side to be high as well. The acoustic device <NUM>, when the level of the voice of the talker on a near-end side is low, causes the level of the voice on a far-end side to be low as well. A talker talks quietly in many cases when the surrounding environment is quiet. When a talker talks quietly, sound to be outputted from the speaker <NUM> is also reduced. Accordingly, only the sound to be outputted from the speaker <NUM> is not increased. In other words, the talker does not have to manually adjust volume with caring about the surrounding environment.

It is to be noted that the gain determining portion <NUM> may average the determined gain on a time axis. The gain determining portion <NUM> suppresses a rapid change in volume by averaging a gain on a time axis, and reduces the sense of incongruity that a user feels.

In addition, the acoustic device <NUM> may detect a voice section, and may adjust a gain only in the detected voice section. For example, the acoustic device <NUM> does not need to change a gain during a far-end single talk. In such a case, the acoustic device <NUM> distinguishes a far-end single talk in a case in which the audio signal receiving portion <NUM> receives an audio signal having a level greater than or equal to a predetermined threshold value and the power level of an audio signal inputted from the microphone <NUM> is less than a predetermined value.

In addition, the acoustic device <NUM>, as shown in <FIG>, may remove an echo element by the echo canceller <NUM>. The echo canceller <NUM> generates a pseudo echo element by filtering the audio signal received from the far-end side by transfer characteristics in the environment in which the acoustic device <NUM> is set. The echo canceller <NUM>, by subtracting the pseudo echo element from the audio signal obtained by the microphone <NUM>, removes the echo element. The voice feature amount extracting portion <NUM> extracts a voice feature amount using the audio signal of which the echo element has been removed by the echo canceller <NUM>. In such a case, the voice feature amount extracting portion <NUM> may adjust a gain during the far-end single talk. It is to be noted that the echo canceller <NUM> may be hardware or may be achieved when the CPU <NUM> reads an echo cancellation program from the memory <NUM> and executes the program.

Next, <FIG> is a block diagram showing a functional configuration of an acoustic device <NUM> according to a modification. The same reference numerals are given to components common to the components in <FIG>, and the description will be omitted. The acoustic device <NUM> further includes a noise feature amount extracting portion <NUM>. The noise feature amount extracting portion <NUM> is also achieved by the program of the CPU <NUM>.

The noise feature amount extracting portion <NUM> extracts a noise feature amount from an inputted audio signal. The noise feature amount extracting portion <NUM> obtains a noise level as an example of the noise feature amount. More specifically, the noise feature amount extracting portion <NUM> obtains power level of an audio signal according to noise.

The noise feature amount extracting portion <NUM>, in a case of determining that noise is inputted, obtains a noise level by obtaining the power level of an audio signal. The noise feature amount extracting portion <NUM> determines whether or not noise is inputted, for example, by distinguishing a near-end single talk, a far-end single talk, and a double talk. The noise feature amount extracting portion <NUM> distinguishes a far-end single talk in a case in which the audio signal receiving portion <NUM> receives an audio signal having a level greater than or equal to a predetermined threshold value and the power level of an audio signal inputted from the microphone <NUM> is less than or equal to a predetermined value. The noise feature amount extracting portion <NUM> distinguishes a double talk in a case in which the audio signal receiving portion <NUM> receives an audio signal having a level greater than or equal to a predetermined threshold value and the power level of an audio signal inputted from the microphone <NUM> is greater than or equal to a predetermined value. The noise feature amount extracting portion <NUM> distinguishes a near-end single talk in a case in which the audio signal receiving portion <NUM> receives an audio signal having a level less than a predetermined threshold value and the power level of an audio signal inputted from the microphone <NUM> is greater than or equal to a predetermined value.

The noise feature amount extracting portion <NUM> calculates a noise feature amount in a case of no correspondence to a near-end single talk, a far-end single talk, and a double talk. More specifically, the noise feature amount extracting portion <NUM> obtains the power level of the inputted audio signal as a noise feature amount in a case in which the audio signal receiving portion <NUM> receives an audio signal having a level less than a predetermined threshold value and the power level of an audio signal inputted from the microphone <NUM> is less than or equal to a predetermined value. However, the noise feature amount extracting portion <NUM>, in a case of removing an echo element by the echo canceller <NUM>, may set the power level of an audio signal inputted during a far-end single talk as a noise feature amount. It is to be noted that the noise feature amount may be averaged on a time axis.

It is to be noted that the voice feature amount extracting portion <NUM> may perform noise cancellation processing based on the noise feature amount extracted by the noise feature amount extracting portion <NUM>. For example, the voice feature amount extracting portion <NUM> subtracts the power level of an audio signal that the noise feature amount extracting portion <NUM> has obtained, from the voice feature amount. As a result, the voice feature amount extracting portion <NUM> is able to obtain the power level of an audio signal according to voice with higher accuracy, based on the audio signal of which the noise sound has been removed.

The gain determining portion <NUM> determines a gain, based on the voice feature amount and the noise feature amount that have been extracted by the voice feature amount extracting portion <NUM> and the noise feature amount extracting portion <NUM>. <FIG> is a diagram showing the relationship between the voice feature amount and the gain. As shown in <FIG>, the gain determining portion <NUM> sets the gain higher as the voice feature amount is higher. The gain determining portion <NUM> sets the gain lower as the voice feature amount is lower. Furthermore, the gain determining portion <NUM> sets the gain higher as the noise feature amount is higher. The gain determining portion <NUM> sets the gain lower as the noise feature amount is lower.

Therefore, the acoustic device <NUM> according to a modification, when the level of voice of a talker on a near-end side is high and the noise level is low, causes the level of voice on a far-end side to be low. The acoustic device <NUM>, when the level of the voice of the talker on a near-end side is low and the noise level is high, causes the level of the voice on a far-end side to be high. According to the modification, even when the voice of a talker is loud, sound to be outputted from the speaker <NUM> is reduced when the surrounding environment is quiet. Accordingly, only the sound to be outputted from the speaker <NUM> is not increased. In other words, the talker does not have to manually adjust the volume with caring about the surrounding environment. In addition, according to the modification, even when the voice of a talker is quiet, sound to be outputted from the speaker <NUM> is increased when the surrounding environment is noisy. Accordingly, only the sound to be outputted from the speaker <NUM> is not reduced. In other words, a talker, even when talking in a quiet voice in a noisy environment, can hear voice on the far-end side.

It is to be noted that the noise feature amount extracting portion <NUM> may further detect distant noise. Accordingly, the acoustic device <NUM>, even when a talker other than a user is in a position away from the acoustic device <NUM>, reduces a possibility of erroneously recognizing the voice of a talker on a near-end side.

<FIG> is a diagram showing a functional configuration of the acoustic device <NUM> in a case of detecting distant noise. The acoustic device <NUM> further includes a second microphone 15B and a correlation calculating portion <NUM> in addition to the configuration of <FIG>.

The correlation calculating portion <NUM> receives an input of an audio signal from the microphone <NUM> and the microphone 15B. The correlation calculating portion <NUM> calculates a correlation of two audio signals. The correlation is calculated, for example, by cross-power level spectrum phase analysis.

Distant sound includes a large number of indirect sound elements, and is a sound of which an arrival direction is not fixed. For example, in a case in which the microphone <NUM> has a directivity and the microphone 15B has a non-directivity, sound collection capability with respect to distant sound is greatly different. Therefore, the correlation is reduced in a case of sound from a distant sound source, and is increased in a case of sound from a sound source near the device.

The noise feature amount extracting portion <NUM>, when the correlation calculated by the correlation calculating portion <NUM> is small, distinguishes that sound from the distant sound source has been detected, and sets the power level of the inputted audio signal as a noise feature amount. The voice feature amount extracting portion <NUM>, in a case in which the correlation calculated by the correlation calculating portion <NUM> is large, distinguishes that voice of a talker has been detected, and sets the power level of the inputted audio signal as a voice feature amount. Accordingly, the acoustic device <NUM> is able to obtain the noise feature amount and the voice feature amount with higher accuracy.

<FIG> is a flow chart showing an operation of an acoustic device <NUM> according to a first modification. The acoustic device <NUM> first distinguishes a near-end single talk, a far-end single talk, and a double talk. In other words, the acoustic device <NUM> distinguishes whether or not a far-end single talk is performed (S11).

The acoustic device <NUM>, in a case of distinguishing a far-end single talk (S11: Yes), ends the processing. In other words, the acoustic device <NUM> does not change a gain.

The acoustic device <NUM>, in a case that a far-end single talk is not performed (in a case of a near-end single talk or a double talk) (S11: No), detects background noise from the inputted audio signal (S12).

The acoustic device <NUM> obtains power level of an audio signal according to the detected background noise, and reduces a noise element from the audio signal (S13). Subsequently, the acoustic device <NUM> obtains the power level of the inputted audio signal as a noise feature amount (S14). Finally, the acoustic device <NUM> determines a gain of the audio signal received from the far-end side, based on a voice feature amount and the noise feature amount (S15) and adjusts a level of the received audio signal by the gain (S16).

The processing of S11, S12, and S14 is not required in the present invention. The acoustic device <NUM>, in S13, may determine a gain, based on the voice feature amount extracted by the voice feature amount extracting portion <NUM>, without using the noise feature amount.

It is to be noted that the acoustic device may determine a gain, based on the noise feature amount extracted by the noise feature amount extracting portion <NUM>, without using the voice feature amount. For example, the acoustic device <NUM> increases a gain when the power level of a noise signal is high. In other words, the acoustic device may extract a feature amount from the sound collected by a microphone, and may determine a gain of an audio signal received from a different device on a far-end side, based on the extracted feature amount.

Another acoustic device includes microphone, a noise level obtaining portion that obtains a noise level from sound collected by the microphone, a storage in which a predetermined noise level is stored, an audio signal receiving portion that receives an audio signal from a different device on a far-end side, and a gain determining portion that determines a gain of the audio signal received from the different device on the far-end side, based on the predetermined noise level and a present noise level obtained by the noise level obtaining portion.

The acoustic device determines a level of the audio signal on the far-end side, based on a previously stored noise level and the present noise level. In the acoustic device, the volume of a speaker with respect to the noise level as a reference is automatically determined, so that a user on a near-end side has no difficulty hearing. In addition, the acoustic device reduces the level of the voice on a far-end side, when the present noise level reduces with respect to the noise level as a reference. Accordingly, only the sound to be outputted from the speaker <NUM> is not increased. In other words, the talker does not have to manually adjust the volume with caring about the surrounding environment.

More preferably, the storage stores the noise level obtained by the noise level obtaining portion. The gain determining portion determines a gain of the audio signal received from the different device on a far-end side, based on a previous noise level stored in the storage and the present noise level obtained by the noise level obtaining portion.

In such a case, the acoustic device obtains noise around the device and determines the volume of a speaker, based on the level of the obtained noise sound. Therefore, the acoustic device is able to adjust the volume of a speaker according to a more nearly actual environment.

In addition, the acoustic device may include a volume adjustment receiving portion that receives volume adjustment from a user. The storage may store a noise level when the user adjusts the volume.

In such a case, the acoustic device determines the volume of a speaker, on a basis of a ratio between the noise level and the volume of a speaker that the user manually adjusted. Accordingly, the volume of a speaker is automatically adjusted to a volume that the user feels appropriate.

It is to be noted that the acoustic device may include a distinguishing portion that distinguishes a voice section, and the gain determining portion may determine a gain in the voice section that the distinguishing portion has distinguished. The acoustic device, since performing in a limited(in a each of distinguished) voice section, is able to determine a gain with higher accuracy.

Hereinafter, an acoustic device 1A will be described in more detail. <FIG> is a block diagram showing a functional configuration of the acoustic device 1A. The same reference numerals are given to components common to the components of the acoustic device <NUM> in <FIG>, and the description will be omitted.

The acoustic device 1A further includes a volume adjustment receiving portion <NUM>, and a storage <NUM> that stores a noise feature amount that the noise feature amount extracting portion <NUM> has extracted. The hardware configuration of the acoustic device 1A is the same as the hardware configuration shown in <FIG>. The storage <NUM> is configured by the memory <NUM>. The volume adjustment receiving portion <NUM> is configured by the user I/F <NUM>. The volume adjustment receiving portion <NUM> may be implemented when the CPU <NUM> reads and executes a volume adjustment receive program stored in the memory <NUM>.

The volume adjustment receiving portion <NUM> receives an operation of volume adjustment from a user. The volume adjustment receiving portion <NUM> adjusts the gain of the gain adjusting portion <NUM>, based on the operation of the received volume adjustment.

The noise feature amount extracting portion <NUM> is an example of the noise level obtaining portion. The noise feature amount extracting portion <NUM> is configured by the feature amount extraction program. The noise feature amount extracting portion <NUM> obtains a noise feature amount. The way to obtain the noise feature amount is the same as the way previously described, and, for example, obtains a noise level. The noise feature amount extracting portion <NUM> outputs a noise level to the storage <NUM> when the volume adjustment receiving portion <NUM> receives the operation of volume adjustment. The storage <NUM> stores the noise level when a user adjust the volume. The noise feature amount extracting portion <NUM> outputs the noise level to the gain determining portion <NUM>. The gain determining portion <NUM> determines a gain, based on the previous noise level stored in the storage <NUM> and the present noise level outputted from the noise feature amount extracting portion <NUM>. For example, the gain determining portion <NUM>, in a case in which the present noise level is higher than the previous noise level, increases the gain. Accordingly, the volume of a speaker with respect to the noise level as a reference is automatically determined.

<FIG> is a flow chart showing an operation of the acoustic device 1A. The acoustic device 1A first distinguishes whether or not a noise section is present (S101). As shown in <FIG>, the acoustic device 1A distinguishes the noise section in a case in which a status is not any of a near-end single talk, a far-end single talk, and a double talk. Also, the acoustic device 1A, in a case of removing an echo element by the echo canceller <NUM>, distinguishes a far-end single talk as a noise section. The acoustic device 1A, in a case of distinguishing that no noise section is present (S101: No), ends the processing. In other words, the acoustic device 1A does not perform a gain adjustment when a noise section is not present.

The acoustic device 1A, in a case of distinguishing a noise section (S101: Yes), obtains a noise level, for example, as a noise feature amount (S102). Subsequently, the acoustic device 1A determines whether or not volume adjustment has been received from a user (S103). The acoustic device 1A, in a case of receiving the volume adjustment from a user (S103: Yes), stores the obtained noise level (S104). The acoustic device 1A, in a case of receiving no volume adjustment (S103: No), determines a gain, based on the stored previous noise level and the obtained present noise level (S105). For example, the acoustic device 1A, in the case in which the present noise level is higher than the previous noise level, increases the gain. Accordingly, the volume of a speaker with respect to the noise level as a reference is automatically determined.

It is to be noted that a gain adjustment may be performed to all the bands or may be performed in a limiting predetermined band (such as an FFT band, an octave band, the Mel band, or the Bark band). For example, the voice feature amount extracting portion <NUM> may perform a gain adjustment in a band of <NUM> to <NUM> that has a significant effect on the sensitivity of voice.

In addition, the acoustic device 1A may perform a gain adjustment, based on the obtained noise feature amount. For example, the acoustic device 1A performs a gain adjustment according to a noise spectrum. The acoustic device 1A sets a gain high in a band in which a noise level is high. Accordingly, surrounding people except a user are less likely to feel noisy about the sound outputted from the speaker <NUM>.

In addition, the acoustic device 1A may perform a gain adjustment according to human auditory characteristics (loudness characteristics). For example, low-frequency and high-frequency gains do not greatly change regardless of a change in noise level.

The above descriptions are illustrative in all respects and should not be construed to be restrictive.

For example, the voice feature amount is not limited to power level. For example, the acoustic device <NUM> may calculate the peak of a low frequency element of a cepstrum obtained by further applying the Fourier transform to the spectrum of an audio signal. The acoustic device <NUM> may normalize a peak value of the low frequency element of a cepstrum, may convert the value into a value of <NUM> to <NUM>, and may extract the value as a voice feature amount. Similarly, the noise feature amount is not limited to power level.

In addition, the storage does not need to be built in the acoustic device 1A. For example, the storage may be provided in a server. In such a case, the acoustic device 1A obtains a noise level from the storage of the server.

It is to be noted that all the configurations of the present invention may be implemented by hardware such as FPGA. For example, as shown in <FIG>, the acoustic device <NUM> or the acoustic device 1A may include a feature amount extraction circuit 51A corresponding to the voice feature amount extracting portion <NUM> or the noise feature amount extracting portion <NUM>, a gain determination circuit 52A corresponding to the gain determining portion <NUM>, an audio signal reception circuit 53A corresponding to the audio signal receiving portion <NUM>, and a gain adjusting circuit 54A corresponding to the gain adjusting portion <NUM>. As a matter of course, the configuration of the present invention may be implemented by appropriately combining hardware and software.

Claim 1:
An acoustic device (<NUM>) comprising:
a microphone (<NUM>);
a voice feature amount extracting portion (<NUM>) that is configured to extract a voice feature amount from a first audio signal representing sound collected by the microphone (<NUM>);
a noise feature amount extracting portion (<NUM>) that is configured to extract a noise feature amount including a noise level from the first audio signal;
an audio signal receiving portion (<NUM>) that is configured to receive a second audio signal from a different device (<NUM>) on a far-end side;
a gain determining portion (<NUM>) that is configured to determine a gain of the second audio signal based on the extracted voice feature amount and the extracted noise feature amount, wherein the gain determining portion (<NUM>) is configured to set the gain higher as the extracted voice feature amount is higher, wherein the gain determining portion (<NUM>) is configured to set the gain lower as the extracted voice feature amount is lower, wherein the gain determining portion (<NUM>) is configured to set the gain higher as the extracted noise feature amount is higher, wherein the gain determining portion (<NUM>) is configured to set the gain lower as the extracted noise feature amount is lower, wherein the gain determining portion (<NUM>) is configured to set the gain limited to values equal to or lower than one, and wherein the gain determining portion (<NUM>) is configured to set the gain linearly proportional to the voice feature amount; and
a gain adjusting portion (<NUM>) that is configured to adjust the second audio signal based on the determined gain of the second audio signal,
wherein the noise feature amount extracting portion (<NUM>) is configured to calculate a power of the first audio signal as the noise feature amount in a case that
the power of the first audio signal is less than or equal to a predetermined value, and
a power of the second audio signal received by the audio signal receiving portion (<NUM>) is less than a predetermined threshold value.