JP2002204493A - Zoom microphone system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom microphone system that can pick up an object sound with sufficient emphasis at a telescopic position depending on a zoom position. SOLUTION: A sound pickup section 11 transduces a sound wave into a sound signal, a zoom control section 12 outputs a zoom position signal corresponding to a zoom position, a directivity control section 13 changes the directivity depending on the zoom position signal so as to pick up a sound with emphasis on a sound wave arriving mainly in a front direction to provide outputs of an R channel sound signal and an L channel sound signal at a telescopic position, and a noise suppression section 14 suppresses a background noise included in each channel sound signal at the telescopic position at a higher degree than that at a wide angle position. Thus, the zoom microphone system can pick up a sufficiently emphasized object sound at the telescopic position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom microphone device, and more particularly, to a zoom microphone device having an audio zoom function for effectively emphasizing and collecting a target sound in accordance with a zoom position.

[0002]

2. Description of the Related Art Conventionally, in a video camera or a digital camera capable of shooting a moving image, a zoom microphone device capable of zooming in a target sound in conjunction with a zoom-up operation of a lens and collecting sound with a high SNR has been used. Have been. As a method for realizing zoom sound pickup, a method of performing simple frequency correction or a method of changing the directional characteristic of a microphone by digital signal processing is adopted. Hereinafter, conventional zoom microphone devices employing these methods will be briefly described with reference to the drawings.

FIG. 21 shows, as a first conventional example, a configuration of a zoom microphone device which realizes zoom sound pickup by simple frequency correction. The zoom microphone device is
A sound pickup unit 900, a zoom control unit 901 and a high-pass filter 902 are provided. The sound collection unit 900 converts a sound wave into a sound signal. The zoom control unit 901 outputs a zoom position signal for determining a zoom position. The high-pass filter 902 emphasizes the high frequency range of the audio signal from the sound pickup unit 900 with a frequency characteristic according to the zoom position signal. Specifically, the higher the zoom position is on the telephoto side, the more the high-frequency portion of the audio signal is emphasized.

The sound wave input to the sound pickup unit 900 contains a target sound and background noise. Usually, at the time of telephoto, the target sound is emitted from a place away from the zoom microphone device. By the way, ambient noise generally has a spectrum that is biased toward a low band. Therefore, at the time of telephoto, the low-frequency portion of the audio signal output from the sound pickup unit 900 is converted to a high-pass filter 9.
02, the ratio of the background noise included in the audio signal is relatively reduced. By this, SN at the time of telephoto
R is improved, and a zoom effect is obtained.

FIG. 22 shows, as a second conventional example, a configuration of a zoom microphone device that realizes zoom sound pickup by changing directional characteristics by digital signal processing. The zoom microphone device includes a sound collection unit 903, a zoom control unit 904, a directivity control unit 905, and a volume control unit 906. The sound collection unit 903 includes microphone units 907a and 907b. Directivity control unit 905
Represents an adder 908 and amplifiers 909, 910a, 910
b, 910c and adders 911a, 911b.

[0006] Microphone units 907a, 907b
Are installed at an angle to the front direction. The adder 908 includes a microphone unit 907
a, the audio signal from 907b is added. Amplifier 909
Multiplies the amplitude of this audio signal by 0.5. Amplifier 910
a, 910b, and 910c change the amplitude of the audio signal from the microphone units 907a and 907b and the amplifier 909, respectively, according to the zoom position signal from the zoom control unit 904. Specifically, at the time of wide angle, the amplification degree of the amplifiers 910a and 910b is set to 1, and the amplifier 910c
Is 0. On the other hand, at the time of telephoto, the amplifier 910
a, 910b the amplification degree is 0, and the amplification degree of the amplifier 910c is 1. Adder 911a adds the output of amplifier 910c to the output of amplifier 910a, and outputs an R-channel audio signal. Adder 911b adds the output of amplifier 910c to the output of amplifier 910b, and outputs an L-channel audio signal.

The sound wave input to the sound pickup unit 903 includes a target sound and background noise. Normally, at telephoto, the target sound is emitted from the front of the zoom microphone device,
On the other hand, background noise is emitted from various directions. Therefore, when the directivity of the R channel and the L channel is changed in the front direction during telephoto, the ratio of the background noise included in the audio signal of each channel is relatively reduced. Thereby, the SNR at the time of telephoto is improved, and a zoom effect can be obtained.

The volume control section 906 is provided in the zoom microphone device according to the second conventional example.
In general, the source of the target sound is farther at telephoto than at wide angle, so that the volume of the target sound arriving at the zoom microphone device is relatively small. Therefore, at the time of telephoto, the volume control unit 9
By increasing the volume of each channel audio signal by 06, a higher zoom effect can be obtained.

[0009]

However, FIG.
In the first conventional example shown in FIG. 1, not only the low-frequency portion of the ambient noise but also the low-frequency portion of the target sound at the time of telephoto are filtered by the high-pass filter 90.
2, the sound quality of the target sound, that is, the frequency characteristic changes every time the zoom position changes.

In the second conventional example shown in FIG.
If the sound wave arrives from the front at telephoto, not only the target sound but also stationary background noise will be collected.
There is a problem that the effect of improving the density is insufficient.

When the volume at the time of telephoto is increased by volume control, not only the target sound but also background noise increases, so that the effect of improving the SNR cannot be obtained, and the target sound is sufficiently emphasized. There is a problem that can not be.

Therefore, an object of the present invention is to provide a telephoto camera,
The background noise is suppressed without changing the sound quality of the target sound,
It is an object of the present invention to provide a zoom microphone device capable of collecting sound while sufficiently emphasizing a target sound.

[0013]

A first aspect of the present invention is a zoom microphone device having an audio zoom function for effectively picking up a target sound in accordance with a zoom position. Sound collecting means for converting the signal into a signal, zoom control means for outputting a zoom position signal corresponding to the zoom position, directivity control means for changing the directional characteristic of the zoom microphone device itself based on the zoom position signal, and sound collecting means Noise suppressing means for suppressing background noise included in the audio signal converted by the audio signal, and at the time of telephoto, the directivity control means changes the directional characteristic so as to emphasize the target sound, and further includes the background noise included in the audio signal. Is characterized in that it is finally suppressed to a greater degree than at the time of wide angle.

As described above, according to the first aspect of the invention, unnecessary sounds that are collected together with the target sound are reduced by mainly collecting sound waves from the arrival direction of the target sound at telephoto. In addition, by suppressing background noise from the same direction as the target sound included in sound waves collected at telephoto to a greater degree than at wide-angle, the target sound is effective when the zoom position changes from wide-angle to telephoto. Sound can be picked up with emphasis. It should be noted that the "voice" does not refer to only a human voice, but refers to so-called general sound.

According to a second aspect of the present invention, in the first aspect, there is further provided a sound volume control means for increasing the power level of the audio signal at the time of telephoto than at the time of wide angle.

As described above, according to the second aspect of the present invention, the volume of the sound signal picked up at the telephoto is made larger than that at the wide angle, so that it is as if the sound is picked up near the sound source of the target sound. Thus, the target sound can be effectively emphasized and collected. Further, by making the degree of noise suppression at the time of telephoto higher than at the time of wide angle, it is possible to prevent the problem that the volume of background noise increases when the volume is increased at the time of telephoto. Thereby, the target sound can be more effectively emphasized and collected.

In a third aspect based on the first aspect, the directivity control means generates a plurality of channel audio signals based on the audio signals converted by the sound collection means, and the noise suppression means includes a plurality of noise suppression means. A noise suppression unit, based on the zoom position signal, at telephoto,
Background noise included in a plurality of channel audio signals is suppressed to a greater degree than at the time of wide-angle.

As described above, according to the third aspect of the present invention, the background noise contained in each channel audio signal is wide-angled at telephoto by performing noise suppression according to the zoom position on each channel audio signal. It can be suppressed to a greater degree than sometimes.

In a fourth aspect based on the first aspect, the directivity control means generates a plurality of channel audio signals based on the audio signals converted by the sound collection means, and the noise suppression means includes a plurality of channel audio signals. Estimating means for estimating the amount of background noise included in a plurality of channel audio signals based on at least one channel audio signal among the audio signals, and background noise included in each channel audio signal based on the estimation result by the estimating means And a plurality of suppression means for suppressing the above.

As described above, according to the fourth aspect, the background noise amount is estimated based on at least one audio signal,
Since the background noise included in each channel audio signal is suppressed based on the estimation result, the configuration of the device is reduced compared to a case where the background noise is suppressed by individually calculating the background noise amount for each of the plurality of channel audio signals. It is possible to simplify and reduce the processing load.

In a fifth aspect based on the fourth aspect, the estimating means has an averaging means for averaging a plurality of channel audio signals to generate one audio signal, and the averaging means generates the one audio signal. The method is characterized by estimating the amount of background noise included in a plurality of channel audio signals based on the audio signals.

As described above, according to the fifth aspect, the amount of background noise to be suppressed is set more appropriately, so that the amount of background noise contained in each channel audio signal differs greatly. Even if it does, the amount of background noise to be suppressed from each channel audio signal can be kept at an appropriate value without greatly erroneous estimation due to the averaging effect.

In a sixth aspect based on the first aspect, the directivity control means includes a target sound signal for emphasizing a sound wave from the arrival direction of the target sound and another sound signal at a ratio corresponding to the zoom position signal. The noise suppression means includes a mixing means for mixing, and is applied to only the target sound signal, and suppresses background noise included in the target sound signal to a certain degree.

As described above, according to the sixth aspect of the present invention, noise suppression is performed only on the target sound signal to a certain degree. Background noise can be suppressed. Therefore, it is not necessary to control the degree of noise suppression for each of the audio signals according to the zoom position signal, and the configuration of the apparatus can be simplified.

In a seventh aspect based on the first aspect, the noise suppression means includes a Wiener filter.

As described above, according to the seventh aspect, noise suppression means can be realized by using a general Wiener filter.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below with reference to the drawings. In these various embodiments, control of the directional characteristics of the microphone device and suppression processing of background noise are performed according to the zoom position. Specifically, during telephoto, the directional characteristics are changed so that only the target sound is picked up, and the degree of suppression of background noise is made larger than at wide-angle.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
1 shows a configuration of a zoom microphone device according to an embodiment. 1, the zoom microphone device includes a sound pickup unit 11, a zoom control unit 12, a directivity control unit 13, a noise suppression unit 14, and a volume control unit 15. Sound pickup unit 1
1 includes microphone units 16a and 16b. The directivity control unit 13 includes an adder 17 and amplifiers 18 and 19.
a, 19b and 19c and adders 20a and 20b. The noise suppression unit 14 includes the noise suppression units 21a and 21
b. Hereinafter, the operation of the first embodiment will be described.

The microphone units 16a and 16b
It is unidirectional, converts sound waves into electrical signals and outputs them as audio signals. However, the term "voice" does not refer to only a human voice, but refers to so-called general sound. The directions of the microphone units 16a and 16b are open in the left and right directions, respectively, so that sound pickup with a sense of reality can be achieved. The audio signal output from the microphone unit 16a is supplied to the adder 17 and the amplifier 19a. On the other hand, the audio signal output from the microphone unit 16b is supplied to the adder 17 and the amplifier 19b. The adder 17 includes a microphone unit 16a,
The audio signals respectively output from 16b are added. As a result, an audio signal is generated in which sound waves arriving mainly from the front direction are emphasized. The audio signal generated by the adder 17 is supplied to an amplifier 18. Amplifier 18
The amplitude of this audio signal is multiplied by 0.5. This is adder 1
7, the amplitude of the audio signal generated by the amplifier 19a
Alternatively, it is to prevent the amplitude of the audio signal supplied to the amplifier 19b from becoming too large. The audio signal output from the amplifier 18 is supplied to the amplifier 19c.

The zoom control section 12 outputs a zoom position signal corresponding to the zoom position. Amplifiers 19a, 19b,
19c adjusts the amplitude of the audio signal output from the microphone unit 16a, the microphone unit 16b, and the amplifier 18 based on the zoom position signal from the zoom control unit 12, respectively. Specifically, at the time of wide angle, the amplifications of the amplifiers 19a and 19b are both 1 and the amplification of the amplifier 19c is 0. On the other hand, at the time of telephoto, the amplifications of the amplifiers 19a and 19b are both 0,
The amplification degree of c becomes 1. Further, in the section between the wide angle and the telephoto, the amplification of the amplifiers 19a, 19b, 19c changes between 0 and 1 according to the zoom position.

The adder 20a adds the audio signals output from the amplifiers 19a and 19c, and outputs the result as an R channel audio signal. The adder 20b is connected to the amplifier 19
b, add the audio signals respectively output from 19c,
Output as an L-channel audio signal. Amplifier 19a,
Since the amplification degrees of 19b and 19c are respectively adjusted according to the zoom position as described above, these R-channel audio signals and L-channel audio signals are output from the microphone units 16a and 16b at the wide angle. On the other hand, at the time of telephoto, both become the same as the audio signal output from the amplifier 18. In the section between the wide angle and the telephoto, each audio signal is mixed at a ratio corresponding to the zoom position. Therefore, the directional characteristics of the R channel and the L channel are the same as the directional characteristics of the microphone units 16a and 16b, respectively, at the time of wide angle. However, as the zoom position changes to the telephoto side, the directivity of each channel gradually increases in the front direction. , And finally the directivity of each channel becomes the front direction.

The R-channel audio signal and the L-channel audio signal output from the adders 20a and 20b are supplied to noise suppression units 21a and 21b, respectively. The noise suppression units 21a and 21b suppress background noise included in the R-channel audio signal and the L-channel audio signal to a degree corresponding to the zoom position signal output from the zoom control unit 12, respectively. Specifically, the noise suppression units 21a and 21b, as shown in FIG.
Background noise contained in each channel audio signal is suppressed to a greater degree than at wide angle. FIG. 3 shows a configuration example of the noise suppression unit 21a. The configuration shown in FIG. 3 is an example in which a Wiener filter is used for the noise suppression unit 21a. Hereinafter, the configuration and operation of the noise suppression unit 21a will be described with reference to FIG. Note that the noise suppression unit 21b has the same configuration as that of the noise suppression unit 21a, and a description thereof will be omitted.

The noise suppression unit 21a includes an FFT 22
, A power spectrum conversion unit 23, a noise spectrum learning unit 24, a suppression amount estimation unit 25, a Wiener filter estimation unit 26, a filter coefficient derivation unit 27, and a filtering calculation unit 28. The R channel audio signal output from the directivity control unit 13 is supplied to the FFT 22 and the filtering operation unit 28. The FFT 22 analyzes the frequency of the audio waveform. The power spectrum conversion unit 23
The power spectrum of the data after the frequency analysis by T22 is calculated. The power spectrum output from the power spectrum conversion unit 23 is supplied to a noise spectrum learning unit 24 and a Wiener filter estimation unit 26. The noise spectrum learning unit 24 includes a power spectrum conversion unit 23
The noise spectrum of the power spectrum output from is detected and the noise spectrum is learned. The suppression amount estimation unit 25 determines the amount of noise spectrum to be suppressed based on the noise spectrum output from the noise spectrum learning unit 24. The Wiener filter estimator 26 calculates a ratio between the power spectrum before noise suppression and the power spectrum after noise suppression based on the outputs from the power spectrum converter 23 and the suppression amount estimator 25. The filter coefficient deriving unit 27
The above ratio, that is, the transfer function is inverse fast Fourier transformed (IFF
T) to return to the waveform on the time axis to make an impulse response. The filtering operation unit 28 filters the audio waveform of the R channel audio signal based on the impulse response obtained by the filter coefficient derivation unit 27. In such a noise suppression unit 21a, various methods can be considered as a method of changing the degree of suppression of background noise according to the zoom position signal from the zoom control unit 12. A typical method will be described below.

As a first example, a method of controlling the suppression amount estimating unit 25 based on the zoom position signal output from the zoom control unit 12 as shown in FIG. 4 can be considered. Specifically, the variable α in the following equation is controlled according to the zoom position signal.

(Equation 1) In this case, for example, at the time of wide angle, noise suppression is not performed by setting α = 0, or the degree of noise suppression is reduced by setting α = 0.1, and the degree of noise suppression is increased by setting α = 0.8 at telephoto.

As a second example, a method of controlling the Wiener filter estimator 26 based on the zoom position signal output from the zoom controller 12 as shown in FIG. 5 can be considered. FIG. 6 is a block diagram illustrating an example of the configuration of the Wiener filter estimating unit 26. In FIG. 6, a variable β is called a flooring variable, and plays a role of suppressing overdrawing of a noise signal. The flooring variable β is controlled according to the zoom position signal. In this case, for example, at the time of wide angle, β = 1 is set, and noise suppression is not performed.
The degree of noise suppression is made small, such as 0.9, and the degree of noise suppression is made large, such as β = 0.2, at telephoto.

As a third example, a method of controlling the filter coefficient deriving unit 27 based on the zoom position signal output from the zoom control unit 12 as shown in FIG. 7 can be considered.
Specifically, as shown in FIG. 8, a variable γ representing the rate of change of the filter coefficient of the time-varying filter is controlled according to the zoom position signal. In this case, for example, at a wide angle, the filter coefficient is fixed at γ = 0, or the change rate of the filter coefficient is reduced at γ = 0.1 or the like.
8, the rate of change of the filter coefficient is increased.

As long as the degree of suppression of the background noise can be changed according to the zoom position signal as shown in FIG. 2, the noise suppression units 21a and 21b may be of any type. For example, a spectral subtraction method or a frequency subband noise suppression method using a filter bank may be used instead of the above-described noise suppression method using a Wiener filter.

The R-channel audio signal and the L-channel audio signal output from the noise suppression units 21a and 21b are supplied to the volume controller 15. The volume control unit 15 changes the power levels of these two channel audio signals according to the zoom position signal output from the zoom control unit 12. Specifically, the power level of each channel audio signal is changed so that the volume of each channel at the time of telephoto is higher than at the time of wide angle. Generally, at the time of telephoto, the target sound comes from a distant place, so that the volume of the target sound collected by the sound collecting unit 11 is smaller than at the time of wide angle. Therefore, the sound volume at the time of telephoto is made larger than that at the time of wide angle by the sound volume controller 15. Thereby, the target sound is emphasized at the time of telephoto, and the user can feel the effect of the audio zoom. Although the volume control unit 15 is not an essential component in the present invention, it is preferable to include the volume control unit 15 from the viewpoint of improving the zoom effect.

As shown in FIG. 9, a configuration in which a frequency characteristic correction unit 29 is provided downstream of the noise suppression unit 14 or the like is also conceivable. In FIG. 9, the same components as those in FIG. 1 are denoted by the same reference numerals. It is known that a problem occurs in that the frequency characteristics of the audio signal from the sound pickup unit 11 change in the course of the signal processing in the directivity control unit 13. The frequency characteristic correction unit 29 is provided to correct the change in the frequency characteristic. In this embodiment, since the signal processing operation of the directivity control unit 13 depends on the zoom position signal,
The change in the frequency characteristic also depends on the zoom position signal. Therefore, in order to always keep the frequency characteristics of the audio signal in a normal state, the frequency characteristic correction unit 29 always performs optimal correction according to the zoom position signal. Although the frequency characteristic correction unit 29 is not an essential component in the present invention, it is preferable that the frequency characteristic correction unit 29 be provided from the viewpoint of preventing sound quality change.

As described above, according to the first embodiment,
When the zoom position changes from wide angle to telephoto, the directional characteristic is changed so that the target sound in the distant place is emphasized and collected, and at the same time, the degree of suppression of background noise included in the collected sound wave is increased. Thus, even when the zoom position changes from a wide angle to a telephoto position, background noise can be suppressed and the target sound can be emphasized and collected without the sound quality of the target sound changing unnaturally. Also, by increasing the volume of the audio signal in accordance with this change in the zoom position, it is possible to effectively emphasize the target sound as if it were picked up near the sound source of the target sound. it can. Also, at this time, the degree of noise suppression increases with an increase in volume, so that there is no problem that background noise increases with an increase in volume.

In the present embodiment, the directional characteristic is changed so that sound waves arriving from the front direction during telephoto are emphasized and collected, but the direction in which sound is to be collected is not limited to the front direction. This is because, when telephoto, it is not essential to emphasize and collect the sound coming from the front, but it is essential to emphasize and collect the target sound when telephoto. In other words, since the direction in which the target sound arrives is not necessarily the front direction, depending on the usage of the zoom microphone device, the directional characteristics should be changed so that the target sound arriving from directions other than the front direction is emphasized and collected. It is possible. Further, the arrival direction of the target sound changes every moment, and the directivity may be dynamically changed so as to follow the direction.

In the first embodiment, the configurations of the sound pickup unit 11 and the directivity control unit 13 are merely examples, and various modifications are conceivable. For example, the number of microphone units included in the sound pickup unit is not limited to two. Further, the number of channel audio signals output from the directivity control unit is not limited to two. Hereinafter, this modified example will be described.

As a first modification, the sound pickup unit 11 and the directivity control unit 13 of the first embodiment shown in FIG.
A zoom microphone device replaced by the sound collection unit 30 and the directivity control unit 31 shown in FIG.

In FIG. 10, the sound pickup unit 30 includes microphone units 32a, 32b, and 32c. The directivity control unit 31 includes adders 33a, 33b, and
5, 36, an adder 37, and equalizers 38a, 38
b, 38c, amplifiers 39a, 39b, 39c, and adders 40a, 40b.

Microphone units 32a, 32b, 3
3c is omnidirectional. The microphone units 32a, 32b, and 33c convert sound waves into sound signals and supply the sound signals to the directivity control unit 31. The delay unit 35 delays the audio signal from the microphone unit 32c by the time for transmitting the sound wave between the microphone units 32a and 32c. The adder 33a subtracts the audio signal output from the delay unit 35 from the audio signal output from the microphone unit 32a, and forms directivity in the direction from the microphone unit 32c to the microphone unit 32a.
Similarly, the adder 33b subtracts the audio signal output from the delay unit 35 from the audio signal output from the microphone unit 32b, and forms directivity in the direction from the microphone unit 32c to the microphone unit 32b. The adder 34 includes the microphone units 32a and 32
Add the audio signal from b. The delay unit 36 delays the audio signal from the microphone unit 32c by the time required for the sound wave to travel between the intermediate point between the microphone units 32a and 32b and the microphone unit 32c. The adder 37 subtracts the audio signal output from the delay unit 36 from the audio signal output from the adder 34, and outputs the signal from the microphone unit 32c to the microphone units 32a and 32a.
The directivity in the direction of the waypoint 2b is configured. The equalizers 38a, 38b, and 38c respectively include adders 33a,
The distortion of the amplitude frequency characteristic and the change in the sound quality that occur when the audio signal is added to or subtracted from the audio signal output from the audio signals 33b and 37 are corrected.

The amplifiers 39a, 39b and 39c adjust the amplitudes of the audio signals output from the equalizers 38a, 38b and 38c, respectively, based on the zoom position signal from the zoom control unit 12. Specifically, at wide angle,
The amplification degrees of the amplifiers 39a and 39b are both 1 and the amplification degree of the amplifier 39c is 0. On the other hand, at the time of telephoto, the amplifications of the amplifiers 39a and 39b are both 0, and
The amplification degree of 9c is 1. In the section between the wide angle and the telephoto, the amplification of the amplifiers 39a, 39b, 39c changes between 0 and 1 according to the zoom position. The adder 40a
The audio signals respectively output from the amplifiers 39a and 39c are added and output as an R channel audio signal. The adder 40b adds the audio signals output from the amplifiers 39b and 39c, and outputs the result as an L-channel audio signal. The directivity of the L channel and the R channel gradually changes in the front direction as the zoom position changes to the telephoto side, and finally, the directivity of either channel becomes the front direction. When two microphone units are used as shown in FIG. 1, a directional characteristic as shown in FIG. 11 is obtained at the time of telephoto. On the other hand, when three microphone units are used as in the present modified example, at the time of telephoto. FIG.
2 is obtained. That is, in the present modified example, the directivity can be made sharper in the front direction than in the first embodiment shown in FIG. As a result, in the present modified example, sound waves arriving from the front direction at the time of telephoto can be more emphasized and collected. As described above, the performance of the zoom sound pickup differs depending on the configuration of the sound pickup unit and the directivity control unit. However, these configurations should be optimally selected by the designer in consideration of other conditions such as cost.

Thereafter, the R-channel audio signal and the L-channel audio signal output from the adders 40a and 40b are noise-suppressed by the noise suppression units 21a and 21b, respectively, to a degree corresponding to the zoom position signal.

Next, as a second modification, the first modification shown in FIG.
A zoom microphone in which the sound pickup unit 11, the directivity control unit 13, and the noise suppression unit 14 of the embodiment are replaced with a sound pickup unit 41, a directivity control unit 42, and a noise suppression unit 43 shown in FIG. The device will be described.

In FIG. 13, the sound pickup section 41 includes microphone units 44a, 44b, 44c, and 44d.
The directivity control unit 42 includes delay units 45c and 45d, adders 46d and 46d, delay units 47c and 47d, and an adder 4
8a, 48b and equalizers 49a, 49b, 49c,
49d, an adder 50, and amplifiers 51a, 51b, 51
c, 51d, an amplifier 52, and adders 53a, 53b. In FIG. 14, the noise suppression unit 43 includes noise suppression units 54a, 54b, 54e.

Microphone units 44a, 44b, 4
4c and 44d are omnidirectional. The microphone units 44a, 44b, 44c, and 44d convert sound waves into audio signals and supply the audio signals to the directivity control unit 42. Delay device 4
5c delays the audio signal from the microphone unit 44c by the time for transmitting the sound wave between the microphone units 44a and 44c, and the adder 46c outputs the audio signal output from the delay unit 45c from the audio signal output from the microphone unit 44a. The signal is subtracted to form directivity from the microphone unit 44c to the microphone unit 44a. The delay unit 45d delays the audio signal from the microphone unit 44d by the time for transmitting the sound wave between the microphone units 44b and 44d.
6d subtracts the audio signal output from the delay unit 45d from the audio signal output from the microphone unit 44b, and forms directivity in the direction from the microphone unit 44d to the microphone unit 44b. Delay unit 47
c delays the audio signal from the microphone unit 44c by the time for transmitting the sound wave between the microphone units 44b and 44c, and the adder 48d outputs the audio signal output from the delay unit 47c from the audio signal output from the microphone unit 44b. The signal is subtracted to form directivity from the microphone unit 44c to the microphone unit 44b. The delay unit 47d delays the audio signal from the microphone unit 44d by the time required for the sound wave to travel between the microphone units 44a and 44d.
a subtracts the audio signal output from the delay unit 47d from the audio signal output from the microphone unit 44a, and forms directivity in the direction from the microphone unit 44d to the microphone unit 44a. Equalizer 4
9a, 49b, 49c, 49d are respectively
The distortion of the amplitude frequency characteristic and the change of the sound quality, which occur when the audio signal is added to or subtracted from the audio signal output from a, 48b, 46c, and 46d, are corrected.

The adder 50 includes equalizers 49c and 49d.
Are added together. Amplifiers 51a, 5
1b, 51c, 51d are equalizers 49a,
The amplitude of the audio signal output from 49b, 49c, 49d is adjusted according to the zoom position signal output from the zoom control unit 12. Specifically, at the time of wide angle, the amplifier 51
a, 51b are both 1 and the amplifiers 51c,
Both the amplification degrees of 51d become 0. On the other hand, at telephoto,
The amplifications of the amplifiers 51a and 51b are both 0, and the amplifications of the amplifiers 51c and 51d are both 1. In the section between the wide angle and the telephoto, the amplifiers 51a, 51b, 51b
The amplification degrees of c and 51d change between 0 and 1 depending on the zoom position. The amplifier 52 multiplies the amplitude of the audio signal output from the adder 50 by 0.5 and outputs it as a C-channel audio signal. The adder 53a adds the audio signals output from the amplifiers 51a and 51c, and outputs the result as an R channel audio signal. The adder 53b includes the amplifier 51
b, add the audio signals respectively output from 51d,
Output as an L-channel audio signal. The directivity of the L channel and the R channel gradually changes in the front direction as the zoom position changes to the telephoto side, and finally, the directivity of either channel becomes the front direction.

Thereafter, the R-channel audio signal, the L-channel audio signal, and the C-channel audio signal output from the adders 53a and 53b and the amplifier 52 are respectively shown in FIG.
In the noise suppression units 54a, 54b and 54e shown in FIG. 4, the noise is suppressed to a degree corresponding to the zoom position signal.

As described above, in the first embodiment, the number of microphone units included in the sound collection unit is not limited to two, and the number of channel audio signals output from the directivity control unit is not limited to two. . FIG. 15 shows a more general configuration according to the first embodiment. The zoom microphone device illustrated in FIG. 15 includes a sound pickup unit 55 that converts sound waves into sound signals and outputs M sound signals, a zoom control unit 12 that outputs a zoom position signal, and a zoom according to the zoom position signal. A directivity control unit 56 that changes the directivity of the microphone device to output N channel audio signals, and N noise suppression units 58a, 58b,... Provided for each of the N channel audio signals. , And a noise suppression unit 57 including 58n. A feature of the first embodiment is that noise suppression is performed on each channel audio signal in accordance with the zoom position. As shown in FIG.
The number M of the audio signals output from the device and the number N of the channel audio signals output from the directivity control unit 56 are arbitrary.

In the present embodiment, the directivity control unit 56
Although a noise suppression unit is provided for each channel audio signal output from, the place where the noise suppression unit is provided is not limited to this. For example, it may be provided for an audio signal output from the sound pickup unit, or may be provided for an audio signal exchanged between components inside the directivity control unit. In the present embodiment, each noise suppression unit is a noise suppression unit corresponding to one channel. However, the present invention is not limited to this, and a noise suppression unit corresponding to a plurality of channels may be used.

As described above, according to the first embodiment,
By changing the directional characteristics so that sound waves from the direction of arrival of the target sound are picked up at telephoto, and suppressing the background noise contained in the collected sound waves to a greater degree than at wide angle, the zoom position can be changed from wide angle. When changing to telephoto, the target sound can be emphasized and collected without changing the sound quality. Also, by raising the volume especially at telephoto,
The target sound can be picked up as if it were picked up near the target sound. In addition, since background noise is suppressed to a greater degree during telephoto than at wide-angle, it is possible to prevent an increase in the volume of background noise due to zoom-up.

(Second Embodiment) As described above, in the first embodiment, noise suppression is individually performed for each audio channel. However, in the second embodiment to be described below, the first embodiment will be described. , The configuration and processing are simplified by sharing a part of the configuration of the noise suppression unit provided for each audio channel with each channel. Hereinafter, the second embodiment will be described.

FIG. 16 shows a configuration of a zoom microphone device according to the second embodiment of the present invention. The zoom microphone device includes a sound pickup unit 11, a zoom control unit 12, a directivity control unit 13, and a noise suppression unit 59. The noise suppression unit 59 includes an estimation unit 60 and suppression units 61a and 61b. In FIG. 16, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The directivity control unit 13 changes the directivity of the zoom microphone device according to the zoom position signal from the zoom control unit 12, and outputs an R channel audio signal and an L channel audio signal. The R channel audio signal output from the directivity control unit 13 is supplied to the estimation unit 60 and the suppression unit 61a, and the L channel audio signal output from the directivity control unit 13 is also supplied to the estimation unit 60 and the suppression unit 61b. You.

FIG. 17 shows a configuration example of the estimating unit 60. The estimation unit 60 includes an averaging unit 62, an FFT 22, a power spectrum conversion unit 23, a noise spectrum learning unit 24,
Suppression amount estimator 25 and Wiener filter estimator 26
And a filter coefficient deriving unit 27. In FIG. 17, the same components as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. Averaging section 62 averages the R-channel audio signal and the L-channel audio signal output from directivity control section 13 to generate one audio signal. Thereafter, in each component of the estimation unit 60, processing based on this audio signal is executed, and finally the filter coefficient derivation unit 27
In, an impulse response for suppressing background noise is obtained at a degree corresponding to the zoom position signal.

In FIG. 16, the suppression units 61a and 61b
As an example, it has the same configuration as the filtering operation unit 28 shown in FIG. 4, and based on the impulse response obtained in the filter coefficient derivation unit 27, removes background noise included in the R channel audio signal and the L channel audio signal, respectively. Oppress.

As described above, according to the second embodiment,
Rather than individually performing noise suppression for each channel audio signal, the amount of noise suppression for each channel audio signal is determined based on one channel audio signal obtained by averaging a plurality of channel audio signals. It is possible to simplify the processing and reduce the processing load for noise suppression.

In the present embodiment, the estimation unit 60 determines the amount of noise suppression based on an audio signal obtained by averaging two channel audio signals of an R channel audio signal and an L channel audio signal. Not exclusively. For example, the noise suppression amount may be determined based on an audio signal obtained by mixing these two channel audio signals at an appropriate ratio, or the noise suppression amount may be determined based on only one of the two channel audio signals. The amount may be determined. However,
In consideration of the case where the amounts of noise suppression determined from the R-channel audio signal and the L-channel audio signal are significantly different, it is more optimal to suppress the noise based on the averaged audio signal of each channel audio signal. This is preferable because noise can be suppressed.

In the present embodiment, the configuration and processing are simplified by sharing a part of the configuration of the noise suppression unit provided for each audio channel in the first embodiment with each channel. , The estimating unit 60 and the suppressing units 61 a and 62 depending on which configuration is shared.
The configuration of a changes. For example, the suppression units 61a and 61b may each include the filter coefficient derivation unit 27 in FIG. In the present embodiment, the zoom position signal from the zoom control unit 12 is used for controlling the suppression amount estimation unit 25, but is not limited to this. In other words, it is only necessary to control based on the zoom position signal so that the degree of noise suppression at the time of telephoto is greater than at the time of wide angle. Therefore,
Depending on the configurations of the estimation unit and the suppression unit, the zoom control unit 1
There may be a configuration in which the zoom position signal from the second unit 2 is supplied to each suppression unit.

As in the first embodiment, as long as the degree of suppression of the background noise can be changed as shown in FIG. 2 according to the zoom position signal, the estimation unit 60 and the suppression units 61a and 61b Anything is fine. For example, a spectral subtraction method or a frequency subband noise suppression method using a filter bank may be used instead of the above-described noise suppression method using a Wiener filter.

As in the first embodiment, the sound pickup unit 11
Various modifications can be considered for the configuration of the directivity control unit 13. FIG. 18 shows a more general configuration according to the second embodiment. The zoom microphone device illustrated in FIG. 18 includes a sound pickup unit 55 that converts sound waves into sound signals and outputs M sound signals, a zoom control unit 12 that outputs a zoom position signal, and a zoom according to the zoom position signal. Directivity control unit 56 that changes the directional characteristics of the microphone device and outputs N channel audio signals, and estimates that estimates a noise spectrum based on at least one channel audio signal of the N channel audio signals. And an N suppression unit for suppressing background noise included in each channel audio signal based on an output of the estimation unit 64. A feature of the second embodiment is that a part of the configuration of the noise suppression unit is shared by each channel. As shown in FIG.
Also, the number N of channel audio signals output from the directivity control unit 56 is arbitrary.

(Third Embodiment) As described above, in the first and second embodiments, the background noise of the channel audio signal is reduced by the noise suppression unit, the estimation unit, and the suppression unit to a degree corresponding to the zoom position signal. In the third embodiment described below, background noise included in a target sound signal, which will be described later, is suppressed to a certain degree, and the target sound signal after the background noise is suppressed and another audio signal. By mixing according to the zoom position signal, as a result, background noise of the channel audio signal is suppressed to a degree corresponding to the zoom position signal.
In the third embodiment, this simplifies the configuration and processing. Hereinafter, the third embodiment will be described.

FIG. 19 shows a configuration of a zoom microphone device according to the third embodiment of the present invention. The zoom microphone device includes a sound pickup unit 11, a zoom control unit 12, and a directivity control unit 66. The directivity control unit 66 includes an adder 17, an amplifier 18, a noise suppression unit 67, and a mixing unit 68. The mixing unit 68 includes the amplifiers 19a and 19
b, 19c and adders 20a, 20b. In FIG. 19, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The sound pickup unit 11 converts sound waves into sound signals and outputs two sound signals. One of these two audio signals is supplied to an adder 17 and an amplifier 19a,
The other is supplied to the adder 17 and the amplifier 19b. The adder 17 adds the two audio signals from the sound pickup unit 11 and outputs an audio signal mainly including sound waves from the arrival direction of the target sound at the time of telephoto (hereinafter, referred to as a target sound signal).
The amplifier 18 multiplies the amplitude of the target sound signal by 0.5. The target sound signal output from the amplifier 18 is supplied to the noise suppression unit 67. The noise suppression unit 67 suppresses background noise included in the target sound signal to a certain degree. Two sound signals from the sound pickup unit 11 and the noise suppression unit 67
Are supplied to the mixing section 68 together. The mixing unit 68 mixes these three signals at a ratio according to the zoom position signal from the zoom control unit 12 to calculate R
A channel audio signal and an L channel audio signal are generated and output.

A description will be given of how the background noise of the channel audio signal is suppressed by the above operation to a degree corresponding to the zoom position signal. At wide angle, the amplifier 19
a, 19b, and 19c each have, for example, 1,
1, 0. That is, the R-channel audio signal and the L-channel audio signal output from the directivity control unit 66 at the time of wide angle are two audio signals output from the sound pickup unit 11, respectively. No suppression has taken place. On the other hand, during telephoto, the amplifier 19
a, 19b, and 19c are 0, respectively.
0 and 1. That is, the R-channel audio signal and the L-channel audio signal output from the directivity control unit 66 during telephoto are both target sound signals output from the noise suppression unit 67, and the noise suppression is performed on the target sound signal. The unit 67 performs noise suppression to a certain degree. When the zoom position is between the wide-angle position and the telephoto position, the R-channel audio signal and the L-channel audio signal output from the directivity control unit 66 include two audio signals output from the sound collection unit 11 and a noise suppression unit. The target sound signal output from the output signal 67 is mixed at a predetermined ratio. Therefore, 2 output from the directivity control unit 66
The relationship between the zoom position and the degree of noise suppression in one channel audio signal results in the relationship shown in FIG.

As described above, according to the third embodiment,
The degree of suppression of background noise at telephoto can be made larger than at wide-angle without providing a plurality of noise suppression units 67 and without directly controlling the degree of noise suppression in the noise suppression unit 67 by the zoom position signal. Therefore, the configuration of the device can be further simplified, and the processing load for noise suppression can be further reduced.

As the noise suppression unit 67, for example, the above-described noise suppression method using a Wiener filter, a spectral subtraction method, or a noise suppression method for a frequency sub-band using a filter bank can be used.

As in the first embodiment, the sound pickup unit 11
Various modifications of the configuration of the directivity control unit 66 are possible. FIG. 20 shows a more general configuration according to the third embodiment. The zoom microphone device illustrated in FIG. 20 includes a sound pickup unit 55 that converts sound waves into sound signals and outputs M sound signals, a zoom control unit 12 that outputs a zoom position signal, and a zoom according to the zoom position signal. A directivity control unit 69 that changes the directivity of the microphone device and outputs N channel audio signals. The directivity control unit 69 includes a noise suppression unit 67 that suppresses background noise included in the target sound signal to a certain degree, and a target sound signal and other (L−1) voices at a ratio corresponding to the zoom position signal. Mixing unit 70 that mixes the signals with each other and outputs audio signals for each channel
And The feature of the third embodiment is that the background noise of the target sound signal mainly including sound waves from the arrival direction of the target sound at the time of telephoto is suppressed to a certain degree, and the target sound signal is changed according to the zoom position signal. As shown in FIG. 20, the number of audio signals output from the sound collection unit 55, the number L of audio signals mixed in the mixing unit 70, The number N of channel audio signals output from the sex control section 56 is arbitrary. In the directivity control unit 69 shown in FIG. 20, the L audio signals including the target audio signal supplied to the mixing unit 70 may include the audio signal itself output from the sound collection unit or 55, An audio signal synthesized based on the audio signal output from the sound collection unit 55 may be included.

In the second embodiment or the third embodiment, the sound volume control section 15 shown in FIG. 1 and / or the frequency characteristic correction section 29 shown in FIG. In addition, it is possible to prevent a change in the frequency characteristic of the audio signal due to the subtraction processing of the audio signal.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a zoom microphone device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining an operation of the noise suppression unit.

FIG. 3 is a block diagram illustrating a configuration example of a noise suppression unit.

FIG. 4 is a block diagram illustrating a configuration example of a noise suppression unit.

FIG. 5 is a block diagram illustrating a configuration example of a noise suppression unit.

FIG. 6 is a diagram for explaining an operation of a Wiener filter estimating unit;

FIG. 7 is a block diagram illustrating a configuration example of a noise suppression unit.

FIG. 8 is a diagram for explaining a variable γ representing a rate of change of a filter coefficient.

FIG. 9 is a block diagram illustrating a configuration of a modification of the first embodiment;

FIG. 10 is a block diagram showing a part of the configuration of a zoom microphone device according to a first modification;

FIG. 11 is a diagram illustrating a directional characteristic of the zoom microphone device according to the first embodiment at a telephoto position.

FIG. 12 is a diagram illustrating a directional characteristic at a telephoto time of a zoom microphone device according to a first modified example.

FIG. 13 is a block diagram showing a part of the configuration of a zoom microphone device according to a second modification.

FIG. 14 is a block diagram showing a part of the configuration of a zoom microphone device according to a second modification.

FIG. 15 is a block diagram showing a more general configuration of the zoom microphone device according to the first embodiment.

FIG. 16 is a block diagram illustrating a configuration of a zoom microphone device according to a second embodiment of the present invention.

FIG. 17 is a block diagram illustrating a configuration of an estimation unit.

FIG. 18 is a block diagram illustrating a more general configuration of a zoom microphone device according to a second embodiment.

FIG. 19 is a block diagram illustrating a configuration of a zoom microphone device according to a third embodiment of the present invention.

FIG. 20 is a block diagram illustrating a more general configuration of a zoom microphone device according to a third embodiment.

FIG. 21 is a block diagram showing a configuration of a zoom microphone device according to a first conventional example.

FIG. 22 is a block diagram showing a configuration of a zoom microphone device according to a second conventional example.

[Explanation of symbols]

Reference Signs List 11 sound pickup unit 12 zoom control unit 13 directivity control unit 14 noise suppression unit 15 volume control unit 16a, 16b microphone unit 17 adder 18 amplifier 19a, 19b, 19c amplifier 20a, 20b adder 21a, 21b noise suppression unit 22 FFT 23 Power spectrum conversion unit 24 Noise spectrum learning unit 25 Suppression amount estimation unit 26 Wiener filter estimation unit 27 Filter coefficient derivation unit 28 Filtering calculation unit 29 Frequency characteristic correction unit 30 Sound collection unit 31 Directivity control unit 32a, 32b, 32c Microphone unit 33a, 33b Adder 34 Adder 35 Delayer 36 Delayer 37 Adder 38a, 38b, 38c Equalizer 39a, 39b, 39c Amplifier 40a, 40b Adder 41 Sound collection unit 42 Directivity control unit 43 Noise suppression unit 4 a, 44b, 44c, 44d Microphone unit 45c, 45d Delay device 46c, 46d Adder 47c, 47d Delay device 48a, 48b Adder 49a, 49b, 49c, 49d Equalizer 50 Adder 51a, 51b, 51c, 51d Amplifier 52 Amplifier 53a, 53b Adders 54a, 54b, 54c, 54d Noise suppression unit 55 Sound collection unit 56 Directivity control unit 57 Noise suppression unit 58a, 58b, 58n Noise suppression unit 59 Noise suppression unit 60 Estimation unit 61a, 61b Suppression unit 62 Average Conversion unit 63 noise suppression unit 64 estimation unit 65a, 65b, 65n suppression unit 66 directivity control unit 67 noise suppression unit 68 mixing unit 69 directivity control unit 70 mixing unit

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshihide Ishimoto 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 5D015 DD02 EE05 5D020 BB04 BB07

Claims (7)

[Claims] 1. A zoom microphone device having an audio zoom function for effectively emphasizing a target sound in accordance with a zoom position, comprising: a sound collecting means for converting a sound wave into an audio signal; and a zoom corresponding to the zoom position. Zoom control means for outputting a position signal; directional control means for changing the directional characteristics of the zoom microphone device itself based on the zoom position signal; and suppressing background noise included in the audio signal converted by the sound collection means. And a directional control unit that changes the directional characteristics so as to emphasize the target sound at the time of telephoto, and that the background noise included in the audio signal finally has a greater degree than at the time of wide angle. A zoom microphone device characterized by being suppressed by: 2. The zoom microphone device according to claim 1, further comprising volume control means for increasing a power level of the audio signal at a telephoto time as compared with a wide angle. 3. The directivity control unit generates a plurality of channel audio signals based on the audio signal converted by the sound collection unit; the noise suppression unit includes a plurality of noise suppression units; 2. The noise suppression unit according to claim 1, wherein based on the zoom position signal, during telephoto, background noise included in the plurality of channel audio signals is suppressed to a greater degree than at wide angle. 3. Zoom microphone device. 4. The directivity control unit generates a plurality of channel audio signals based on the audio signal converted by the sound collection unit, and the noise suppressing unit generates at least one of the plurality of channel audio signals. Estimating means for estimating the amount of background noise included in the plurality of channel audio signals based on one channel audio signal; and a plurality of estimating means for suppressing background noise included in each audio signal based on an estimation result by the estimating means. The zoom microphone device according to claim 1, further comprising a suppression unit. 5. The estimating means includes averaging means for averaging the plurality of channel audio signals to generate one audio signal, and based on the audio signals generated by the averaging means, The zoom microphone device according to claim 4, wherein the amount of background noise included in the channel audio signal is estimated. 6. The directivity control unit generates a target sound signal for emphasizing a sound wave from an arrival direction of the target sound and a plurality of channel signals based on the sound signal converted by the sound collecting unit, The directivity control unit includes a mixing unit that mixes a target sound signal for emphasizing a sound wave from the arrival direction of the target sound and another audio signal at a ratio according to the zoom position signal, and the noise suppressing unit includes: Only applies to the target sound signal,
2. The zoom microphone device according to claim 1, wherein background noise included in the target sound signal is suppressed to a certain degree. 7. The zoom microphone device according to claim 1, wherein said noise suppression means includes a Wiener filter.