JP3154151B2 - Microphone device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microphone device which can be used in a wide range, such as a microphone mounted on a camera-integrated VTR and a microphone for speech / singing. This is a great effect for microphone devices.

[0002]

2. Description of the Related Art A microphone converts a change in sound pressure due to sound waves into mechanical vibration of a diaphragm, and operates an electroacoustic conversion system based on the mechanical vibration to obtain an electric signal. Many. For this reason, when a desired sound is picked up by a microphone, if mechanical vibration is applied to the diaphragm due to some factor other than the desired sound, this becomes noise for the desired sound. In this case, if the above-mentioned factor is wind, noise due to wind (hereinafter referred to as wind noise)
Occurs.

[0003] Methods of reducing wind noise generated in a microphone include: (1) use of a windscreen (windshield); (2) use of an electric / acoustic high-pass filter; and (3) omnidirectionality in a low frequency range. In the past, the adoption of such a method has been widely used.

[0004]

However, in the above method (1), the wind noise generally decreases as the external dimensions of the windscreen increase and as the distance between the microphone element and the inner wall of the windscreen increases. Therefore, there is a problem that a large windscreen must be prepared in order to sufficiently reduce the wind noise. This problem greatly hinders miniaturization and portability of the device.

Further, since wind noise is mainly noise in a low frequency range, the method of using the fixed electric / acoustic high-pass filter of (2) above is effective, but if wind noise is to be reduced. At the same time, there is a disadvantage that the bass range of the desired sound source is also reduced, and the sound pickup quality is reduced.

Further, the method (3) is used because the wind noise is lower when the microphone is omnidirectional than when it is directional. However, the effect of reducing the wind noise by this method is not so large, and in addition, the wind noise does not actually reach a sufficiently low level due to the influence of the housing when configuring the microphone device.

The applicant has previously proposed, as Japanese Patent Application No. 3-349274, a method of avoiding the above problems and sufficiently reducing wind noise.
This method uses an adaptive noise canceller.

FIG. 8 is a block diagram showing the configuration of an example of the microphone device proposed earlier. In FIG.
0 is an adaptive noise canceller. First, the adaptive noise canceller will be described.

In the adaptive noise canceller 10, 1 is a main input terminal, 2 is a reference input terminal, and a main input signal input through the main input terminal 1 is supplied to a synthesis circuit 4 via a delay circuit 3. The reference input signal input through the reference input terminal 2 is applied to the adaptive filter circuit 5.
, And is subtracted from the signal from the delay circuit 3. The output of the synthesizing circuit 4 is fed back to the adaptive filter circuit 5 and is output to an output terminal 6.

In this adaptive noise canceller, a signal obtained by adding a desired signal s and an uncorrelated noise signal n0 is input as a main input signal. On the other hand, a noise signal n1 is input as a reference input signal. The noise signal n1 of the reference input is uncorrelated with the desired signal s, but is correlated with the noise signal n0.

The adaptive filter circuit 5 filters the reference input noise signal n1 and outputs a signal y approximating the noise signal n0. In this case, in the adaptive filter circuit 5, the combining circuit 4
Is updated so as to minimize the subtraction output (residual output) e of the reference input noise signal n1.

As an output signal y of the adaptive filter circuit 5, a signal having the same phase and the same amplitude as the noise signal n0 can be obtained. The delay circuit 3 compensates for a time delay required for the arithmetic processing in the adaptive filter circuit 5, a propagation time in the adaptive filter, and the like, and adjusts the time with the signal to be subjected to the subtraction processing.

The principle of the adaptive noise canceller will be described below.

Now, assuming that the desired signal s, the noise n0, the noise n1, and the output signal y are statistically stationary and the average value is 0, the residual output e is e = s + n0-y. The expected value despite the squared it, because the desired signal s is the noise n0, and the output y ^{uncorrelated, E [e 2] = E} [s 2] + E [(n0 -y) 2] + 2E [s (n0 -y)] = a ^{E [s 2] + E [} (n0 -y) 2]. Assuming that the adaptive filter circuit 5 converges,
The adaptive filter circuit 5 updates the adaptive filter coefficients so that E [e ² ] is minimized. At this time, since the E [s ^2] is not affected, and ^{Emin [e 2] = E [} s 2] + Emin [(n0 -y) 2].

That is, by minimizing E [e ² ], E [(n 0 −y) ² ] is minimized, and the output y of the adaptive filter circuit 5 becomes an estimated amount of the noise signal n 0.
The expected value of the output from the combining circuit 4 is the desired signal s
Only. That is, adjusting the adaptive filter circuit 5 to minimize the total output power is equivalent to the fact that the subtraction output e becomes the least square estimation value of the desired audio signal s.

The adaptive filter circuit 5 can be realized by either an analog signal processing circuit or a digital signal processing circuit.
A digital processing circuit using an SP (Digital Signal Processor) is used.

In the example of FIG. 8, a microphone device for reducing wind noise using the adaptive noise canceller 10 described above is realized as follows. That is, in the microphone device of FIG. 8, two microphone elements 11 and 12 are arranged close to each other. These microphone elements 11 and 12 have the same characteristics, and for example, a non-directional microphone unit is used.

The output of one of the microphone elements 11 is converted into a digital signal by the A / D converter 13, and the digital signal is supplied to the main input terminal 1 of the adaptive noise canceller 10 as a main input signal. The output of the other microphone element 12 is converted into a digital signal by the A / D converter 14, and the digital signal is supplied to the subtraction circuit 15.

In the subtraction circuit 15, the difference between the digital signal output from the microphone element 11 from the A / D converter 13 and the digital signal output from the other microphone element 12 is obtained, and the difference output is referred to. The input signal is supplied to the reference input terminal 2 of the adaptive noise canceller 10.

The signal obtained at the output terminal 6 of the adaptive noise canceller 10 is converted back to an analog signal by the D / A converter 16 and is led out to the output terminal 17 as an output signal of the microphone device.

The operation of the microphone device shown in FIG. 8 for reducing wind noise will be described. When sound is collected in an environment where wind noise is generated by the microphone device, the outputs of the microphone elements 11 and 12 include wind noise in the collected sound signal.

As described above, since the two microphone elements 11 and 12 are arranged close to each other, sound is picked up in a state where the two microphone elements 11 and 12 have a very strong correlation. You. On the other hand, wind noise generated in the microphone element 11 and the microphone element 12 due to the wind is unique to each microphone element.
There is no correlation between the wind noise of both microphone elements.

Therefore, when the subtraction circuit 15 calculates the difference between the outputs of the two microphone elements 11 and 12, the audio signal is canceled, and the subtraction circuit 15 obtains only a component of wind noise. 8, the wind noise component in the output signal of the microphone 11 supplied to the adaptive noise canceller 10 as a main input has a correlation with the wind noise component from the subtraction circuit 15, and the wind noise component from the subtraction circuit 15 has a correlation. As described above, since the noise component is the reference input of the adaptive noise canceller 10, the wind noise in the main input to the output terminal 17 is sufficiently reduced by the adaptive noise canceller 10.

As described above, according to the configuration shown in FIG. 8, the wind noise can be reduced as described above, but the distortion of the voice input remains as a problem. That is, as described above, it is assumed that the desired input signal in the adaptive noise canceller has no correlation with the unnecessary noise signal. However, actually, the wind noise of the microphone and the low frequency component of the desired sound are not completely uncorrelated, and as a result, the desired sound signal is not output without distortion.

More specifically, it appears as a phenomenon that non-linear distortion such as modulation distortion is added to the audio signal output, or the audio signal level is reduced. This is particularly remarkable when the audio signal level is relatively high, or when the number of taps is small when the adaptive filter is formed of, for example, a digital FIR filter.

There is a so-called trade-off relationship between the effect of reducing wind noise and the effect of distortion on desired sound. To sufficiently suppress wind noise, adaptive noise reduction processing is used to reduce the desired sound in the main input. To the sound, which defeats the purpose of achieving good sound pickup quality. In addition, if an attempt is made to suppress distortion to the desired sound, the effect of reducing wind noise is reduced, and it is also difficult to obtain good sound pickup quality.

An object of the present invention is to provide a microphone device which can solve the above-mentioned problems and can obtain good sound pickup quality while sufficiently reducing wind noise.

[0028]

In order to solve the above-mentioned problems, a microphone device according to the present invention basically reduces wind noise by applying an adaptive noise canceller. In view of the noise of the subject,
It is characterized in that the adaptive noise canceller is operated only in the bass range of the main input.

That is, according to the microphone device according to the present invention, the first and second microphone elements 11 and 12 arranged close to each other, and the first and second microphones A means 15 for obtaining a differential output of the outputs of the elements, an adaptive noise canceller 10 for adaptively reducing a noise component included in the main input signal based on the reference input signal, and a first microphone element 11 A first filter 21 for extracting a component in a predetermined band equal to or higher than a predetermined frequency in the output signal, and a component in a predetermined band equal to or lower than a predetermined frequency in the output signal of the first microphone element 11 are extracted and extracted. A second filter 22 for supplying a signal component as the main input signal to the adaptive noise canceller 10; and the first and second microphone elements 1 And extracting a predetermined frequency below a predetermined band component of the differential output of 12, the adaptive noise canceler 10 the extracted signal component as the reference input signal
And an adding unit 24 that adds the output signal of the first filter 21 and the output of the adaptive noise canceller 10 and outputs the result to the device.

The first to third filters 21 to 23 are:
This is to limit the adaptive operation to wind noise to some extent, and each can be configured by a band-pass filter. Further, the first filter 21 may be a high-pass filter for that purpose. Second and third filters 22 and 23
Can be configured with a low-pass filter for that purpose.

[0031]

The wind noise of the microphone is in the low frequency range, for example,
This is noise whose main component is 0 Hz or less. On the other hand, audio signals are distributed over about 100 Hz. According to the present invention having the above-described configuration, for example, Equation 1 of the audio signals collected by the first microphone element 11 by the first filter is used.
A middle-high frequency component of 00 Hz or more is extracted. Due to the nature of the wind noise, the output of the first filter hardly includes a component of the wind noise. The output of the first filter 21 is supplied to the adding means 24 as it is.

On the other hand, from the second filter 22, a low-frequency component of the audio signal collected by the first microphone element 11 and a main component of wind noise are obtained. Is done. Similarly, a low-frequency component of the difference between the outputs of the first and second microphone elements 11 and 12, that is, a main component of wind noise, is obtained from the third filter 23.
Is used as a reference input.

In this state, when the adaptive operation is performed, a low-frequency component of the collected sound in which the wind noise component is canceled is obtained as an output signal of the adaptive noise canceller 10. The adding means adds the low-frequency component and the middle and high-frequency components of the collected sound that are not affected by the adaptive processing at all. Since this addition output becomes the device output, wind noise is sufficiently reduced, and a high quality collected voice signal is obtained.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a microphone device according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of a microphone device according to the present invention, and portions corresponding to those in the example of FIG. 8 described above are denoted by the same reference numerals.

By the way, as described above, the wind noise of the microphone is a noise mainly having several hundred Hz or less. On the other hand, audio signals are distributed over about 100 Hz. FIG. 2 shows an example of wind noise and an average power spectrum of an audio signal. In FIG. 2, the solid line 31 is a wind speed of 2 m.
Power spectrum of wind noise at / sec, solid line 3
Reference numeral 2 denotes a power spectrum of wind noise when the wind speed is 4 m / sec, and a solid line 33 denotes a power spectrum of a male voice.

From FIG. 2, the wind noise can be reduced by several hundreds of hours.
It can be seen that it is sufficient to perform the processing for z or less, and it is sufficient to output the frequency components of several hundred Hz or more without being subjected to any processing.

For this reason, in the example of FIG. 1, the output of one of the pair of microphone elements 11 and 12 arranged close to each other is converted into a digital signal by the A / D converter 13. After that, it is supplied to the high-pass filter 21. This high-pass filter 21
The filter has a cut-off frequency of, for example, 700 Hz, and extracts a middle-high-frequency component containing almost no wind noise from the output signal of the microphone element 11.

The output signal of the high-pass filter 21 is connected to the output terminal 6 of the adaptive noise canceller 10 and D /
The signal is supplied to an adder circuit 24 provided between the A converter 16. Instead of the high-pass filter 21, a band-pass filter having a pass band of a frequency band equal to or higher than the required audio band may be used.

The output signal of the A / D converter 13 is also supplied to a band pass filter 22. The band-pass filter 22 has a pass band of, for example, 100 Hz to 700 Hz, and passes a low-frequency component of the microphone element 11 and a main component of wind noise. Note that the frequency above the pass band of the band-pass filter 22 does not necessarily have to match the cut-off frequency of the high-pass filter 21. The output signal of this bandpass filter 22 is
The main input is supplied to the main input terminal 1 of the adaptive noise canceller 10.

The digital signal of the difference signal between the microphone element 11 and the microphone element 12 from the subtraction circuit 15 is supplied to a band-pass filter 23 having the same characteristics as the band-pass filter 22, and only the wind noise component is extracted. This is input to the reference input terminal 2 of the adaptive noise canceller 10.

As shown in FIG. 3, the adaptive filter circuit 5 of the adaptive noise canceller 10 includes an FIR filter type adaptive linear combiner 100 and a filter coefficient operation circuit 110.
Consists of The adaptive filter circuit 5 can be configured as software by a DSP equipped with a microcomputer. In this example, an LMS (least mean square) method, which is frequently used because the amount of calculation is small and practical, is used as an algorithm for updating the filter coefficient.

The LMS method will be described with reference to FIG. As shown in FIG. 3, the adaptive linear combiner 100
The plurality of delay circuits DL1, DL2 having a delay time Z ^-1 of each unit sampling time, ...... DLm (m
Is a positive integer), input noise n1 and each delay circuit DL1,
DL2,... Weighting circuits MX0, MX1, MX for multiplying the output signal of DLm by a weighting coefficient (filter coefficient)
2,... MXm and an adder 101 for adding outputs of the weighting circuits MX0 to MXm. The output of the adding circuit 101 is the signal y described in the example of FIG.

The weighting coefficients supplied to the weighting circuits MX0 to MXm are formed in the filter coefficient calculation circuit 110 by the LMS algorithm based on the residual signal e from the synthesis circuit 4 and the reference input n1. The algorithm executed by the filter coefficient operation circuit 110 is as follows.

Now, the input vector X _k at time k is
As shown in FIG. 3, X _k = [x _0k x _1k x _2k ... X _mk ] ^T , the output is y _k , and the weighting factor is w _jk (j = 0, 1, 2,... M). Then, the relationship between the input and output is as shown in the following equation 1.

[0045]

(Equation 1) Becomes

Then, the weight vector W _{k at} time _k
Is defined as W _k = [w _{0 k} w _{1 k} w _{2 k} ... W _mk ] ^T , the input / output relationship is given by y _k = X _k ^T · W _k . Here, assuming that a desired response is d _k , the residual e _k is expressed as follows. _{e k = d k -y k =} d k -X k T · W k in the LMS method, the update of the weight _{vector, W k + 1 = W k} + 2μ · e k · X k ... (1) becomes formula (1 ). Here, μ is a gain factor (step gain) that determines the speed and stability of adaptation.

In the configuration shown in FIG. 1 as described above, the adaptive noise canceller 10 has a main input for only the low frequency range containing the main component of the wind noise among the voices collected by the microphone element 11. The adaptive processing is performed so as to cancel the wind noise in the output of the microphone element 11 which is as follows. As a result, a low-frequency component of the output of the microphone element 11 from which the wind noise has been reduced and removed is obtained at the output terminal 6 of the adaptive noise canceller 10.

The output signal of the adaptive noise canceller 10 and the middle and high frequency components of the output of the microphone element 11 containing almost no wind noise component are added in the addition circuit 24. The sound pickup sound signal of the microphone element 11 in which the noise component is reduced can be obtained.

In the case of the example of FIG. 1, distortion may occur depending on the sound level and the setting of the adaptive operation, but the middle and high frequency components of the signal of the microphone element 11 are not affected by the adaptive processing at all. And the high-pass filter 21
, So that the overall improvement in audio quality is fully achieved.

Also, in the example of FIG. 1, the components at 100 Hz or less are included in a large amount in the wind noise, but are hardly included in the audio signal.
Is not used to extract frequency components below 100 Hz. However, a low-pass filter may be used instead of the band-pass filters 22 and 23, and the adaptive noise canceller 10 may also perform noise reduction processing on frequency components of 100 Hz or less.

FIG. 4 is a block diagram showing another embodiment of the microphone device according to the present invention. In this example, since the reference input of the adaptive noise canceller 10 indicates the magnitude of the wind noise at that time, by detecting the magnitude of the reference input signal level, the adaptive noise canceller 1 is detected.
0 controls the adaptive processing operation.

That is, in the example of FIG. 4, the output signal of the band-pass filter 23 is supplied as a reference input to the adaptive noise canceller 10 and also to the level detection circuit 25, where the signal level is detected. . Then, the level detection output of the level detection circuit 25 is supplied to the filter coefficient calculation circuit 110 of the adaptive filter circuit 5 of the adaptive noise canceller 10 as a control signal for updating the coefficient. Others are the same as the example of FIG.

The filter coefficient calculation circuit 110 receives the output of the level detection circuit 25 and receives a reference input signal (that is,
The magnitude of the step gain μ in the above-described filter coefficient update equation (1) is controlled in accordance with the level of the wind noise. That is, when the wind noise is large, the step gain μ is set to be large in order to increase the noise reduction effect of the adaptive noise canceller 10, and when the wind noise is small, the noise reduction effect of the adaptive noise canceller 10 needs to be significantly increased. Therefore, the step gain μ is set smaller. In this way, it is possible to prevent the audio signal from being difficult to hear due to wind noise.

FIG. 5 is a block diagram showing another embodiment of the microphone device according to the present invention. In the example of FIG. 1, since the output of the high-pass filter 21 hardly includes wind noise, it can be said that this output mainly includes the middle and high frequency components of the audio signal. Therefore, this high-pass filter 2
The magnitude of the level of the output signal of No. 1 can be interpreted as indirectly representing the magnitude of the audio signal. In the example of FIG. 5, in consideration of the above points, the operation of the adaptive noise canceller is controlled according to the level of the output signal of the high-pass filter 21, as in the example of FIG.

That is, in the example of FIG. 5, the output signal of the high-pass filter 21 is supplied to the adding circuit 24 and also to the level detecting circuit 26, and the signal level is detected. Then, the level detection output of the level detection circuit 26 is supplied to the filter coefficient calculation circuit 110 of the adaptive filter circuit 5 of the adaptive noise canceller 10 as a control signal for updating the coefficient. Others are the same as the example of FIG.

The filter coefficient calculation circuit 110 receives the output of the level detection circuit 26 and updates the filter coefficient according to the output signal level of the high-pass filter 21 (that is, the audio signal level). Is controlled. That is, for example, when the audio level is high, it is not necessary to increase the noise reduction effect of the adaptive noise canceller 10 so much. Therefore, the step gain μ is set to be small, and when the audio level is low, the step gain μ is set to be large. To control. Thus, also in this example, distortion applied to the audio signal can be appropriately reduced, and good sound collection quality can be obtained.

FIG. 6 is a block diagram showing still another embodiment of the microphone device according to the present invention. This example makes use of the fact that comparing the reference input of the adaptive noise canceller 10 and the level of the output signal of the high-pass filter 21 will (indirectly) monitor the signal-to-noise ratio at that time. .

That is, if the audio signal level is relatively sufficiently higher than the wind noise level, it is not necessary to increase the noise reduction effect of the adaptive noise canceller 10 so much, but rather it is preferable to give priority to maintaining good audio quality. . Conversely, when the wind noise level is relatively large, it is better to increase the noise reduction effect of the adaptive noise canceller 10 and to improve the signal-to-noise ratio even if the sound quality is slightly sacrificed. Therefore, in the example of FIG. 6, the adaptive operation of the adaptive noise canceller 10 is controlled according to the signal-to-noise ratio at that time.

In order to realize this, in the example of FIG. 6, the output signal of the high-pass filter 21 and the output signal of the band-pass filter 23 are supplied to a level ratio detection circuit 27. , The level ratio of both signals is detected. Then, this level ratio detection circuit 2
The level ratio between the two signals detected at 7 is supplied to the filter coefficient calculation circuit 110 of the adaptive filter circuit 5 of the adaptive noise canceller 10 as a control signal for updating the coefficient. Others are the same as the example of FIG.

The filter coefficient calculation circuit 110 controls the step gain μ in the filter coefficient update equation (1) according to the level ratio. For example, when the signal-to-noise ratio is large, the step gain μ is set small, and when the signal-to-noise ratio is small, the step gain μ is increased. Thus, good sound pickup quality can be obtained.

FIG. 7 is a block diagram showing still another embodiment of the present invention. This example is an example in which a bass range where wind noise is present is divided into a plurality of ways, and processing using an adaptive noise canceller is performed for each divided band. According to this example, since wind noise is adaptively reduced for each divided band, it is possible to reduce wind noise more effectively.

In the example of FIG. 7, the bass range where wind noise exists
This is an example in the case of division. That is, instead of the band-pass filters 22 and 23 in the example of FIG.
Band-pass filters 221 and 231 that divide the 00 Hz band into two bands and use the upper divided band as a pass band;
Band-pass filters 222 and 232 that use the lower divided band as a pass band are provided. Then, the output signal of the A / D converter 13 is connected to the band-pass filters 221 and 2.
22 and the output signal of the subtraction circuit 15 to bandpass filters 231 and 232.

Further, adaptive noise cancellers 51 and 52 are provided according to the number of divided bands. The outputs of the bandpass filters 221 and 222 are supplied to the main input terminals 1 of the adaptive noise cancellers 51 and 52, respectively, and the outputs of the bandpass filters 231 and 232 are supplied to the reference input terminals 2 of the adaptive noise cancellers 51 and 52, respectively. To supply.

In the case of this example, the magnitude of the step gain μ in updating the filter coefficient in the adaptive filter circuit 5 of the adaptive noise cancellers 51 and 52 for each band is set to an appropriate value for each band. However, as in the above-described examples of FIGS. 4 to 6, a configuration may be employed in which the step gain is adaptively controlled according to the level of the reference input or the level of the main input, and furthermore, the level ratio between the two.

The output signals of the adaptive noise cancellers 51 and 52 are supplied to the addition circuit 24,
The signal is added to the middle and high frequency components of the picked-up output signal of the microphone element 11 from 1, supplied to the D / A converter 16, returned to an analog signal, and led to the output terminal 17.

The example shown in FIG. 7 is an example in which the bass range is divided into two parts, but may be divided into three or more parts.

According to the microphone device described above,
Even if a special sensor or the like is not prepared, wind noise can be reduced by preparing two ordinary microphone elements. In this case, the two microphone elements are
Since they are arranged close to each other, it is possible to contribute to miniaturization of equipment.

Further, since two microphone elements can be respectively allocated to the left and right channels, even when a stereo microphone is configured, it can be realized without increasing the number of microphone elements.

According to the examples shown in FIGS. 4 to 6, the wind noise reduction effect of the adaptive noise canceller can be appropriately controlled depending on the magnitude of the wind noise level and the audio signal level, so that good sound pickup quality and wind noise suppression effect can be obtained. Can be obtained at the same time.

Furthermore, since the wind noise reduction operation is automatic, the user can concentrate on other tasks, for example, monitoring a monitor image while shooting with a camera-integrated VTR.

In the above-described example, non-directional microphones are used as the two microphone elements 11 and 12, but these microphone elements may have any directivity. However, if an omnidirectional microphone is used, it is easy to handle and inexpensive, so that the practical effect is great.

It is also easy to obtain another directivity by combining two microphone elements. Moreover,
It is also easy to make it almost omnidirectional in the low frequency range and unidirectional in the middle and high frequency ranges. Of course, it is also possible to obtain a signal according to the gist of the present invention by using three or more microphone elements.

In the above example, the high-pass filter 21, the band-pass filters 22, 23, 221, 2
Cut-off frequency of 22,231,232 has been fixed, as shown in FIG. 2, power scan Puku tram wind noise, considering that frequency changes according to the wind speed, roll-off frequency of these filters As a variable configuration, it can be configured to control to an appropriate cutoff frequency according to the wind speed. The variable cutoff frequency filter
For example, it can be realized by using an IIR digital filter and changing the weighting coefficient.

The change of the cutoff frequency may be performed manually, or may be performed automatically by providing a means for measuring the wind speed.

The A / D converters 13 and 14 may be connected to the output sides of the band-pass filters 22 and 23 without being directly connected to the microphone elements 11 and 12. In that case, the high-pass filter 21 and the band-pass filters 22 and 23 are constituted by analog circuits. Also, D / A
The converter 16 will be inserted at the output of the adaptive noise canceller 10.

A band-pass filter having the same frequency characteristics as the band-pass filters 22 and 23 may be inserted into the output of the adaptive noise canceller.

[0077]

As described above, according to the present invention, in consideration of the fact that wind noise mainly exists in the low-frequency range, the sound collected by the microphone has almost no low-frequency component and almost no wind noise component. Applying an adaptive noise canceller to reduce and remove wind noise only for the low-frequency component, and adding the low-frequency component and the high-frequency component from which the wind noise has been removed to produce an output signal only for the low-frequency component As a result, the middle and high frequency components of the collected voice are not affected by the adaptive noise canceller at all, and a high-quality collected voice output voice signal in which wind noise is sufficiently suppressed can be obtained.

Further, in the present invention, the wind noise reduction effect of the adaptive noise canceller is appropriately controlled according to the magnitude of the wind noise level and the audio signal level, so that a good sound pickup quality and a sufficient wind noise suppression effect are obtained. Can be obtained at the same time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a microphone device according to the present invention.

FIG. 2 is a diagram illustrating an example of an average power spectrum of wind noise and an audio signal.

FIG. 3 is a block diagram illustrating a configuration example of an adaptive filter circuit.

FIG. 4 is a block diagram showing another embodiment of the microphone device according to the present invention.

FIG. 5 is a block diagram showing another embodiment of the microphone device according to the present invention.

FIG. 6 is a block diagram showing another embodiment of the microphone device according to the present invention.

FIG. 7 is a block diagram showing another embodiment of the microphone device according to the present invention.

FIG. 8 is a block diagram showing an embodiment of the microphone device of the prior application.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Adaptive noise canceller 1 Main input terminal 2 Reference input terminal 4 Synthesis circuit 5 Adaptive filter circuit 11, 12 Microphone element 13, 14 A / D converter 15 Subtraction circuit 16 D / A converter 17 Device output terminal 21 High-pass filter 22, 23 Band Pass filter 24 Addition circuit 25, 26 Level detection circuit 27 Level ratio detection circuit

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁷ Identification symbol FI H04R 1/40 320 (72) Inventor Kaoru Gyokutoku 7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (56) References JP-A-4-178100 (JP, A) JP-A-3-292098 (JP, A) JP-A-61-150497 (JP, A) JP-A-3-69996 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) H04R 3/00 320 G10L 15/20 G10L 21/02 H03H 17/04 611 H03H 21/00 H04R 1/40 320

Claims (6)

(57) [Claims] 1. Reference is made to first and second microphone elements arranged close to each other, means for obtaining a differential output between outputs of the first and second microphone elements, and a noise component included in a main input signal. An adaptive noise canceller adapted to adaptively reduce based on an input signal; a first filter for extracting a component in a predetermined band equal to or higher than a predetermined frequency from an output signal of the first microphone element; A second filter that extracts a component in a predetermined band equal to or lower than a predetermined frequency from the output signals of the microphone elements of the above, and supplies the extracted signal component to the adaptive noise canceller as the main input signal; A component of a predetermined band equal to or lower than a predetermined frequency among the differential outputs of the microphone elements is extracted, and the extracted signal component is sent to the adaptive noise canceller as the reference input signal. Kyusuru a third filter, the output signal of the first filter, by adding the output of said adaptive noise canceller, a microphone device and a summing means to supply output. 2. A microphone apparatus according to claim 1, according to the level of the output signal of said third filter, a microphone device and controls the adaptive operation of the adaptive noise canceler. 3. The microphone device according to claim 1, wherein an adaptive operation of the adaptive noise canceller is controlled in accordance with a level of an output signal of the first filter. 4. The microphone according to claim 1, the level of the output signal of the third filter, in accordance with the ratio between the level of said first output signal of the filter, the adaptation of the adaptive noise canceler A microphone device for controlling operation. 5. The microphone device according to claim 1, wherein the second filter divides a band of a predetermined frequency or less in an output signal of the first microphone element into a plurality of bands, and The signal component of each divided band extracted by the second filter is supplied as a main input signal to a plurality of adaptive noise cancellers provided corresponding to each divided band. The third filter divides a band having a frequency equal to or lower than a predetermined frequency out of the differential output of the first and second microphone elements into the plurality of bands, and extracts a component for each divided band. The signal components of the respective divided bands extracted by the third filter are supplied to the plurality of adaptive noise cancellers as reference input signals, respectively, and are output from the first filter. Signal and microphone device being characterized in that the plurality of outputs of said plurality of adaptive noise canceller to be added in the adding means. 6. The microphone device according to claim 1, wherein a cutoff frequency of said first filter and a cutoff frequency of at least one of said second and third filters. A microphone device wherein an off-frequency can be changed.