JPH11259090A - Sound pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a target sound wave signal with noises suppressed even if the target sound wave signal picked up with air conductive microphones is buried in the ambient noises. SOLUTION: Sound wave signals, which are picked up with microphones 1, 2 installed at a position near a sound source of a target sound wave signal and at another position farther than the aforementioned position from the sound source of the target sound wave signal and contain ambient noises, are converted into spectra, respectively (3, 4); a predominant frequency component of the target sound wave signal contained in the microphone 1 is extracted (6) from the level differences (5) of the amplitude spectra of each frequency component; as to unextracted frequency components, a noise level is estimated (8) from the spectral intensities of the unextracted frequency components and attenuated by a noise suppression quantity determined according to the estimated noise level quantity; and such a processed spectrum is converted into a time waveform (11), and consequently, the target sound wave signal is obtained with the noises suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound pickup apparatus having a function of suppressing an ambient noise component from a sound source signal in which ambient noise is mixed and extracting a target signal.

[0002]

2. Description of the Related Art As a conventional technique for extracting a target signal from an SN ratio under noise, there is a method of extracting a frequency component in which the target signal is dominant on a frequency axis using a sound field distribution difference of the target signal. It was proposed in Japanese Patent Application No. Hei 10-39206 "Sound collection device". In the sound collection system of the proposed technique, a main input microphone is installed near a sound source of a target signal, and an auxiliary input microphone is installed at a position farther from the sound source than the main input microphone. By paying attention to the fact that the characteristic of the level difference generated between these two microphones differs between the noise and the target signal, generally, the former is smaller than the latter, thereby realizing the extraction of the frequency component in which the target signal is dominant. .

FIG. 10 shows an example of the proposed technique. The main input microphone 1 (for the near sound source) is arranged at a position close to the sound source of the target signal, and the auxiliary input microphone 2 (for the remote sound source) is arranged apart from the sound source of the target signal. The output signals of these microphones 1 and 2 are frequency components L (ω _h ), R (ω _h ), (h = 1, 2,...
Is decomposed into When the level difference between the frequency components L (ω _h ) and R (ω _h ) decomposed by the level difference calculation unit 5 is larger than a threshold value set from outside, the sound source frequency component selection unit 6 determines whether the target signal is Assuming that the frequency component is dominant, the corresponding frequency component L (ω _m ) (m = i, j,...) Is extracted from the output of the spectrum converter 3. The frequency component suppression unit 10 attenuates the corresponding frequency component L (ω _m ) (m = k, 1,...) In the output of the spectrum conversion unit 3. Sound source frequency component extraction unit 7 and noise frequency component suppression unit 10
Then, the output spectrum of the spectrum conversion unit 3 that has been subjected to such processing is converted into a time waveform by the time waveform conversion unit 11 and output. According to such processing, noise suppression that can be applied to noise that changes unsteadily with time is realized.

[0004]

However, the above technique has a problem that the quality of a processed signal is deteriorated if the attenuation of a frequency component in which a target signal is not dominant is not appropriate. In particular, under the noise of quiet surroundings, if the attenuation of the above frequency component is too large, the loss of the target signal superimposed on the frequency component in which the target signal is not dominant is conspicuous, and the sound quality is apt to be significantly deteriorated in audibility. was there.

An object of the present invention is to control the amount of noise suppression in accordance with the situation of noise so that the target signal superimposed on a frequency component in which the target signal is not dominant is not noticeably lost under quiet noise. It is an object of the present invention to provide a sound pickup device which has little sound quality deterioration, that is, improves the quality of a processed signal in the technique proposed above.

[0006]

According to the first aspect of the present invention, the first microphone installed at a position close to the sound source of the target signal and the second microphone installed at a position farther from the sound source of the target signal than the position. First and second spectrum conversion means convert each output signal from the microphone into an amplitude spectrum and a phase spectrum, and the plurality of spectrum conversions are performed on the amplitude spectrum for each frequency component output from the plurality of spectrum conversion means. The level difference between the means is calculated by the level difference calculating means, and the level difference for each frequency component output by the level difference calculating means is compared with a preset threshold value. The sound source frequency component selection means determines whether the frequency component is present or not, and from the amplitude spectrum of the output signal of the first microphone, the sound source frequency component selection means The frequency component for which the target signal is determined to be dominant is extracted by the sound source frequency component extracting means, and from the amplitude spectrum of the output signal of the first microphone, the target signal is not determined to be dominant by the sound source frequency component selecting means. The frequency components extracted are extracted from the amplitude spectrum, and the amplitude spectrum or output level of noise other than the target signal is estimated by the noise level estimating means from the amplitude spectrum, and according to the amplitude spectrum or output level of the noise output from the noise level estimating means. The noise suppression amount is determined by the noise suppression amount calculation means, and the noise component is determined for the frequency component in which the target signal is not determined to be dominant by the sound source frequency component selection means in the amplitude spectrum of the output signal of the first microphone. The attenuation determined by the suppression amount calculation means is performed by the noise frequency component suppression means, and the sound source frequency Convert time waveform converting means to a time waveform with a phase spectrum calculated amplitude spectrum output from component extraction means and the noise frequency component suppressing means by said first orthogonal transform means.

According to a second aspect of the present invention, in the sound collecting apparatus according to the first aspect, the magnitude of the amplitude spectrum of the frequency component whose target signal is determined to be dominant by the sound source frequency component extracting means is set in advance. The sound source silent section determination means determines that the sound source of the target signal is in a silent state when the amplitude spectrum is smaller than the silent section determination threshold value. When the sound source of the target signal is determined to be in a silent state by the means, the threshold value used for the sound source frequency component selection means is set to be equal to or larger than the level difference output from the level difference calculation means. Is calculated and updated.

According to a third aspect of the present invention, in the sound pickup apparatus according to the first or second aspect, the magnitude of the amplitude spectrum of the frequency component whose target signal is determined to be dominant by the sound source frequency component extracting means is set in advance. The sound source silent section determination means determines that the sound source of the target signal is in a silent state when the amplitude spectrum is smaller than the silent section determination threshold value. When the sound source of the target signal is determined to be in a silent state by the silent section determining means, the "output of the time waveform converting means" or the "output of the sound source frequency component extracting means and the noise frequency component suppressing means" is attenuated by the sound source silent section. Attenuate by means.

According to a fourth aspect of the present invention, in the sound collection device according to the first, second or third aspect, the handset and the head are arranged such that the first microphone is closer to the mouth when used than the second microphone. Set and ear microphone set. First According to the structure of the invention acts according to claim 1, wherein, a determination is made whether the target signal is dominant frequency component by the level difference of the amplitude spectrum of the second microphone, the further object signals, and the sound source Since the positional relationship between the first and second microphones hardly changes and their distance is short, a stable level difference occurs between the two microphones. on the other hand,
Regarding noise, it may be considered that the distance between the sound source and the first and second microphones is longer than the distance between the sound source of the target signal and the first and second microphones. For this reason, it is considered that the level difference caused by the target signal is always larger than the level difference caused by the noise.

According to the present invention, the frequency component in which the target signal is dominant is extracted by focusing on the fact that the level difference between the two microphones differs between the target signal and the noise as described above. For frequency components for which the target signal is not determined to be dominant, that is, for frequency components for which noise superimposition is not negligible, the amplitude spectrum or output level of the noise is estimated from its amplitude spectrum, and the estimated amplitude spectrum of the ambient noise is obtained. Alternatively, an attenuation process according to the output level is performed. According to such processing, it is possible to realize a sound collection device having a noise suppression function, which can be applied to non-stationary noise and can control the amount of noise suppression according to the state of the noise.

According to the second aspect of the present invention, the first aspect is provided.
By calculating and updating a threshold value for determining whether the target signal is a dominant frequency component in the case where the target sound source is determined to be in a silent state in the described invention,
In the sound source frequency component selection means, the accuracy of determining the frequency component in which the target signal is dominant is improved, and the sound quality is improved. According to the third aspect of the present invention, when the sound source of the target signal is determined to be in a silent state in the first or second aspect of the present invention, the "output of the time waveform conversion means" or
By attenuating "the output of the audio frequency component extracting means and the noise frequency component suppressing means", the noise suppressing effect when the target sound source is in a silent state is improved.

According to a fourth aspect of the present invention, in the first, second or third aspect of the present invention, the handset and the head are arranged such that the first microphone is closer to the mouth than the second microphone. By incorporating a set and an ear microphone set, it becomes possible to improve the noise resistance of the transmission signal in each handset.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block diagram showing an embodiment of the present invention. A noise level estimating unit 8 and a noise suppression amount calculating unit 9 are added to those shown in FIG. The processing procedure of the first embodiment will be described with reference to the flowchart of FIG. First, target signals in which noise is superimposed on the microphones 1 and 2 are fetched, and read as digital signals (S02). Hereinafter, the read signals of the microphones 1 and 2 are referred to as L and R, respectively.

The spectrum converters 3 and 4 convert the captured signals L and R into spectra L (ω _h ) and R (ω _h ) (h =
1, 2,..., N) (S03). This conversion is
For example, this is performed by a discrete Fourier transform. The level difference calculator 5 calculates a level difference ΔLR (ω given by the following equation for each frequency component of L (ω _h ) and R (ω _h ).
_h ) is calculated (S04).

ΔLR (ω _h ) = 20 log 10 (| L
_{(Ω h) | / | R} (ω h) |) ω h in the above formula is the frequency (h = 1,2, ..., n ), | L
(Ω _h ) | and | R (ω _h ) | represent the amplitude spectrum components of the L and R signals, respectively. The sound source frequency component selection unit 6 selects a frequency component in which the target signal is dominant based on the magnitude relationship between ΔLR (ω _h ) and a preset threshold value Th (ω _h ) for each frequency component. The condition for determining whether or not the target signal is a dominant frequency component is determined by, for example, the following equation (S05).

[0016] ΔLR (ω _h)> Th in (ω _h) → target signal is dominant _{ΔLR (ω h) ≦ Th (} ω h) → sound source frequency component extraction unit 7 target signal is not dominant, L (ω _h ), The frequency component L (ω _m ) (m = i, j,
Spectral component storage unit a ...) (not shown) to S (omega _m)
(S06).

S (ω _m ) = L (ω _m ) (m = i, j,...) In the audio frequency component selection unit 6, the frequency ω _m (m = k, l) at which the target signal is determined not to be dominant ,...) Perform the following noise suppression processing (S07) to (S10). First, the noise level estimating unit 8 calculates L (ω _h ) (h =
The frequency component L (ω _m ) (m = k, l,...) In which the target signal is not dominant is extracted from 1, 2,.
7). From this L (ω _m ) (m = k, 1,...), An output level Lv over the entire noise band is estimated (S08). As an estimation method, for example, the following equation can be considered.

Lv = 20 log 10 ((n / q) × Σ | L (ω _m ) |) Here, q is the number of frequency components determined that the target signal is not dominant, and the sum Σ is the target signal. Untargeted frequency ω
_m (m = k, 1,...). The noise suppression amount calculation unit 9 calculates a weight coefficient w (ω _m ) (m = k, l,...) By which the frequency component in which the target signal is not dominant is multiplied (S09). For example, the following equation is used to calculate w (ω _m ).

W (ω _m ) = C (Lv <Lv1) C ((Lvh−Lv) / (Lvh−Lv1)) ^npw (Lv1 ≦ Lv ≦ Lvh) 0 (Lv> Lvh) where C is 0 ≦ A constant that satisfies C ≦ 1, Lvh is a measure of a large noise level that requires sufficient noise suppression, Lv1 is a measure of a small noise level that does not need to perform noise suppression so much, and C and npw are w ( ω _m ).

FIG. 6 shows w in the above equation when C = 1.
(Ω _m ) -Lv characteristics are shown. As shown in this figure, when the noise is low, the weight coefficient w (ω _m ) approaches 1. In this case, since the amount of noise suppression is reduced, the problems of signal degradation after processing and residual noise are overcome. Further, under high noise, the weight coefficient w (ω _m ) approaches 0, so that the noise suppression amount increases, and the clarity of the processed signal can be improved.

The noise frequency component suppression unit 10 multiplies the weight coefficient calculated by the noise suppression amount calculation unit 9 by a frequency component L (ω _m ) (m = k, 1,...) Where the target signal is not dominant. Is stored as S (ω _m ) (m = k, 1,...) In a spectrum component storage unit (not shown) after the noise suppression processing (S10). S (ω _m ) = w (ω _m ) × L (ω _m ) Then, S (ω _h ) (h = 1, 2,...) Obtained by synthesizing the output of (S10) and the output of (S06) is a time waveform. The conversion unit 11 converts the signal L into a time waveform using the phase spectrum Φ (ω _h ) and outputs a time waveform signal (S1).
1).

The above processing is based on frame processing.
This is performed by a method in which the time lengths of the signals read in (S02) are shifted and superimposed. For example, if the shift width is halved when the time length is 40 ms, the processes of (S02) to (S12) are repeated at a frame period of 20 ms. Note that the weighting factor calculated in (S09) is calculated according to the output level of the noise in all the bands, and these values are obtained by dividing the noise into a plurality of sub-bands, so that It can be obtained as a value corresponding to the noise output level. Also, instead of noise suppression using a weighting coefficient as in (S09), a noise spectrum is estimated from the amplitude spectrum envelope formed by the output of (S07), and a spectral subtraction process of subtracting from the amplitude spectrum of the signal L is applied. It is also possible. Second Embodiment In the invention according to the first embodiment, the sound source frequency component selection unit 6 externally sets a threshold value Th (ω _h ) for determining whether or not a certain frequency component is dominant in a target signal. . According to the second aspect of the present invention, the threshold value Th (ω _h ) is determined by utilizing the level difference between the frequency components of the microphones 1 and 2 generated in the ambient noise when the sound source of the target signal is in a silent state. By calculating and correcting, the sound source frequency component selection unit 6 improves the accuracy of determining whether or not the target signal is dominant, thereby improving the sound quality.

FIG. 2 shows a second embodiment of the present invention. In this embodiment, a sound source silent section determination unit 12 and a threshold value calculation unit 13 are added to FIG. is there. Hereinafter, the processing in the sound source silent section determination unit 12 and the threshold value calculation unit 13 will be described with reference to FIG. First, the sound source silence section determination unit 12 calculates the sum P of the amplitude spectrum in which the target signal is dominant (S07), and determines the silence of the sound source of the target signal based on the magnitude relationship between P and a threshold value PTh set from outside. The state is detected (S12).

P> PTh → the sound source of the target signal is in a sound state P ≦ PTh → the sound source of the target signal is in a silent state When the sound source silent section determination unit 12 determines that the sound source of the target signal is in a silent state, The threshold value calculation unit 13 calculates a threshold value Th (ω _h ) (h = 1, 2,..., N). For example, a new threshold is calculated by the following equation (S13, S14).

[0025] _{Th (ω h) = ΔLR (} ω h) the invention of Example 3 according to claim 3, wherein _{(ΔLR (ω h)> Th} (ω h) when only) is as claimed in claim 1 or claim 2, wherein In the present invention, when the sound source of the target signal is determined to be in a silent state by the sound source silent section determination unit 12, the “output of the time waveform conversion unit 11” or the “output of the sound source frequency component extraction unit 7 and the noise frequency component suppression unit 10” Is attenuated to improve the noise suppression effect.

As shown by a broken line in FIG. 2, the third embodiment has a sound source silent section attenuating section 14 added to the second embodiment. Except for the operation of the sound source silent section attenuator 14, the operation of the third embodiment is the same as that of the second embodiment. explain.

[0027] In the sound source silent interval damping unit 14, when the sound source object signal is determined to silence the sound source silent section determining unit 12 (S16), the output signal S of the time waveform conversion section 11 (t _h) It is attenuated (S17). The processing of the sound source silent section attenuating unit 14 is performed by the output of the sound source frequency component extracting unit 7 and the noise frequency component suppressing unit 10 as S (ω _h ) (h
= 1, 2,..., N), and the effect is the same as the effect of the processing of (S17). Fourth Embodiment FIG. 3 shows a fourth embodiment. FIG. 3A shows a case where the microphone 1 and the microphone 2 are attached to the handset 21. When the handset 21 is in use, the microphone 1 is positioned near the user's mouth 22, that is, near the sound source of the target signal, and the microphone 2 is positioned near the handset 21 of the handset 21, that is, near the ear 23.

FIG. 3B shows a case where the microphones 1 and 2 are attached to the headset 25 and the microphone 27 is attached to a part of the receiver 27 which is in contact with the ear 23 when the headset 25 is mounted on the head 26 of the user. 2, a support arm 28 is extended from the receiver 27, and the free end of the support arm 28 is located near the mouth 22, where the microphone 1 is mounted.

FIG. 3C shows a case where the ear microphone set 31 is attached to the ear 23 and the arm 32 is extended toward the mouth 22 with the ear microphone set 31 attached to the ear 23.
The microphone 1 is attached thereto, the arm 33 is extended opposite to the arm 32, and the microphone 2 is attached thereto. As shown in FIG.
By incorporating a handset, a headset, and an ear microphone set into the apparatus 2 and configuring an apparatus that realizes the processing of the first to third embodiments, it is possible to improve the noise resistance of the transmission signal in each handset. . Experimental Example An experimental example to which the invention of claim 1 is applied is shown below. The target signal uses voice and the noise signal uses the ambient noise at the platform of the station. The input signals of the microphone 1 and the microphone 2 are input directly from the sound source 41 of the target signal to the microphone 1 as shown in FIG. The microphone 2 was attenuated by 6 dB (halved by electric power) by the resistance element 42 and input, and the noise from the noise source 43 was created on the computer so that it was input to the microphones 1 and 2 at the same level. S
The / N ratio is defined as the ratio of the average power of the target signal to the average power of the noise signal, and the value of the microphone 1 is 5 dB, −
The processing was performed for each of 5 dB. The frequency resolution in the spectral decomposition of the signal was 22 Hz, the time length of the analysis frame was 46 ms, and the frame period was 23 ms.

FIGS. 8A and 8B and FIGS. 9A and 9B show S /
The target signal and the noise signal before the processing of the microphone 1 when N is 5 dB and -5 dB, S / N = 5 in FIGS. 8C and 9C.
dB, S / N = −5 dB, each noise signal + target signal, FIGS. 8D and 9D show S / N = 5 dB, S
This is the processed signal when / N = -5 dB. From these figures, it can be seen that the signal after processing (FIGS. 8D and 9D) well restores the target signal before processing to FIG. 8A and FIG. 9A under the condition that the SN ratio is 5 dB and −5 dB. You can check.

Also, by listening to the headphones, the SN ratio is 5d.
A sound without distortion is obtained with the processed signal of B, and the SN ratio is -5.
It was confirmed that a sufficient noise suppression effect was obtained with the dB processed signal. This indicates that the control of the noise suppression amount is operating well.

[0032]

As described above, according to the first aspect of the present invention, the first signal generator installed at a position close to the sound source of the target signal is used.
The output signals of the microphone and the second microphone installed at a position distant from the sound source of the target signal from the position are converted into an amplitude spectrum and a phase spectrum by first and second spectrum conversion means. A level difference calculator calculates a level difference between the first and second spectrum converters for an amplitude spectrum of each frequency component being output, and calculates a level difference between each frequency component output by the level difference calculator. The sound source frequency component selection means compares the predetermined frequency with a preset threshold value to determine whether or not the target signal is a dominant frequency component. From the amplitude spectrum of the output signal of the first microphone, the sound source frequency component The frequency component for which the target signal is determined to be dominant by the selection means is extracted by the sound source frequency component extraction means, and the output signal of the first microphone is extracted. From the amplitude spectrum, frequency components for which the target signal is not determined to be dominant by the sound source frequency component selection means are extracted, and the amplitude spectrum or output level of noise other than the target signal is estimated from the amplitude spectrum by the noise level estimation means. The noise suppression amount is determined by the noise suppression amount calculation means in accordance with the amplitude spectrum or the output level of the noise output from the noise level estimation means, and the sound source in the amplitude spectrum of the output signal of the first microphone is determined. The frequency components for which the target signal is not determined to be dominant by the frequency component selection means are subjected to attenuation determined by the noise suppression amount calculation means by the noise frequency component suppression means, and the sound source frequency component extraction means and the noise frequency component The amplitude spectrum output from the suppression means is transmitted to the first microphone of the first microphone. By using the phase spectrum calculated by the vector conversion means to convert it to a time waveform by the time waveform conversion means, it operates effectively even for unsteady noise and controls the amount of noise suppression according to the noise situation It is possible to provide a sound collection device having a new noise suppression processing function.

According to a second aspect of the present invention, in the sound pickup apparatus of the first aspect, the magnitude of the amplitude spectrum of the frequency component determined as the dominant signal of the target signal by the sound source frequency component extracting means is set in advance. The amplitude spectrum is smaller than the silent section determination threshold, and the sound source silent section determining section determines that the sound source of the target signal is in a silent state when the amplitude spectrum is smaller than the silent section determination threshold. When the sound source of the target signal is determined to be in the silent state, the threshold value used by the sound source frequency component selection means is updated by the threshold value calculation means so that the threshold value becomes equal to or more than the level difference output from the level difference calculation means. By doing so, it is possible to provide a sound pickup device capable of improving the frequency component extraction accuracy in which the target signal is dominant in the sound source frequency component selection means and improving the quality of the processed signal.

According to a third aspect of the present invention, in the sound collection device of the first aspect, the magnitude of the amplitude spectrum of the frequency component for which the target signal is determined to be dominant by the sound source frequency component extracting means, and the preset silence. Comparing with a section determination threshold, when the amplitude spectrum is smaller than the silent section determination threshold, the sound source silent section determining means determines that the sound source of the target signal is in a silent state, and the sound source silent section determining means When the sound source of the target signal is determined to be in a silent state, the "output of the time waveform converting means" or the "output of the sound source frequency component extracting means and the noise frequency component suppressing means" is attenuated by the sound source silent section attenuating means. By doing so, when the sound source of the target signal is in a silent state, the signal is attenuated, whereby the noise is suppressed, and a sound pickup device with less noise is provided.

According to a fourth aspect of the present invention, in the sound collection device according to the first, second, or third aspect, the first microphone installed at a position close to the sound source of the target signal is separated from the sound source of the target signal. A handset such that, of the second microphones installed at the positions, the former microphone is closer to the mouth when used than the latter microphone,
By being incorporated in the headset and the ear microphone set, it becomes possible to improve the noise resistance of the transmission signal in the conventional handset, headset and ear microphone set. 2. Description of the Related Art Conventionally, as an ear microphone set for obtaining a transmission signal excellent in noise resistance, there is an ear microphone set in which a bone conduction microphone and a receiver are integrated. However, the sound picked up by the bone conduction microphone has a low frequency component and a low frequency component, so that the sound quality is poor. There is also a problem of acoustic coupling between the bone conduction microphone and the receiver. In the present invention, the sound is collected based on the air conduction sound,
Since the distance between the receiver and the microphone can be ensured, an ear microphone set that does not have the above-described problem can be provided.

The microphone used in the above description is not limited to a non-directional microphone.
For example, the microphone 1 uses a microphone having directivity in the direction of the sound source of the target signal, and the microphone 2
May use a microphone having directivity in the direction opposite to the sound source of the target signal. In this case, it can be used as a super-directional microphone having sharp directivity only in the direction of the sound source of the target signal.

The present invention can be used not only for various sound collection devices that require noise suppression, but also for telephone devices for speech communication and voice recognition input devices.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a functional configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a functional configuration of an embodiment of each of the second and third aspects of the present invention.

FIG. 3 is a side view showing various embodiments of the invention of claim 4;

FIG. 4 is a flowchart showing an operation procedure of the embodiment shown in FIG. 1;

FIG. 5 is a flowchart showing an operation procedure of the embodiment shown in FIG. 2;

FIG. 6 shows Lv of w (ω _m ) in the embodiment shown in FIG.
The figure which shows the characteristic example with respect to FIG.

FIG. 7 is a diagram showing a generation example of a microphone input signal used in an experimental example of the present invention.

FIG. 8 is a diagram showing a target signal before processing, a noise signal, a noise + target signal (SN ratio = 5 dB), and a signal after processing applied to the experimental example of the present invention.

FIG. 9 shows a target signal, a noise signal, a noise + target signal (SN ratio = −5 dB) before processing applied to an experimental example of the present invention,
FIG. 3 is a diagram showing signals after processing.

FIG. 10 is a block diagram illustrating an example of a functional configuration of the technology proposed earlier.

Claims (4)

[Claims] A first microphone installed at a position close to a sound source of a target signal; a second microphone installed at a position farther from the sound source of the target signal than the position; and each of the first and second microphones A first and a second spectrum converting means for converting the output signal of FIG. 1 into an amplitude spectrum and a phase spectrum; and calculating a level difference between the amplitude spectrums of the respective frequency components output from the first and the second spectrum converting means. Level difference calculation means, and the level difference for each frequency component output by the level difference calculation means, and compares a predetermined threshold value,
Sound source frequency component selecting means for determining whether or not the target signal is a dominant frequency component; and a frequency at which the target signal is determined to be dominant by the sound source frequency component selecting means from an amplitude spectrum of an output signal of the first microphone. Sound source frequency component extracting means for extracting a component; and extracting, from the amplitude spectrum of the output signal of the first microphone, a frequency component in which the target signal is not determined to be dominant by the sound source frequency component selecting means, and from the amplitude spectrum. Noise level estimation means for estimating the amplitude spectrum or output level of noise other than the target signal; and noise suppression amount calculation for determining the noise suppression amount according to the amplitude spectrum or output level of the noise output from the noise level estimation means. Means, in the amplitude spectrum of the output signal of the first microphone, A noise frequency component suppressing unit that performs attenuation determined by the noise suppression amount calculating unit on frequency components for which the target signal is not determined to be dominant by the wave number component selecting unit; the sound source frequency component extracting unit and the noise frequency And a time waveform converting means for converting the amplitude spectrum output from the component suppressing means into a time waveform using the phase spectrum calculated by the first spectrum converting means. 2. The sound collection apparatus according to claim 1, wherein the magnitude of the amplitude spectrum of the frequency component for which the target signal is determined to be dominant by the sound source frequency component extracting means, and a preset silent section determination threshold value. When the amplitude spectrum is smaller than the silent section determination threshold, the sound source silent section determining means for determining that the sound source of the target signal is in a silent state; and A threshold calculator for calculating and updating a threshold used for the sound source frequency component selector so as to be equal to or more than the level difference output from the level difference calculator when the sound source is determined to be in a silent state; A sound pickup device. 3. The sound pickup device according to claim 1, wherein said sound source frequency component extracting means has a magnitude of an amplitude spectrum of a frequency component whose target signal is determined to be dominant;
Sound source silent section determining means for comparing with a preset silent section determination threshold value, and determining that the sound source of the target signal is in a silent state when the amplitude spectrum is smaller than the silent section determination threshold value; When the sound source of the target signal is determined to be in a silent state by the sound source silent section determining means, the output of the time waveform converting means, or the sound source silent section in which both outputs of the sound source frequency component extracting means and the noise frequency component suppressing means are attenuated. A sound pickup device comprising a damping means. 4. The sound pickup device according to claim 1, wherein the first microphone and the second microphone are selected from the group consisting of the first microphone and the second microphone.
A sound pickup device, wherein the first microphone is incorporated in a handset, a headset, and an ear microphone set such that the first microphone is closer to a mouth when used than the second microphone.