JPS63308499A - Sound collector - Google Patents

Abstract

PURPOSE:To effectively remove only a wind noise by providing a function for detecting the wind noise and controlling a noise suppressing filter according to the detected result. CONSTITUTION:The output of a microphone 1 is separated to a high frequency band signal and a low frequency band signal by a high pass filter 2 and a low pass filter 3. The signals of these two frequency bands are inputted to a high frequency amplitude calculating part 4 and a low frequency amplitude calculating part 5 to obtain the amplitude values of the respective frequency bands. The two amplitude value are inputted to a decision part 6, compared to decide a sound signal or the wind noise. Namely, in the decision part 6, when the amplitude value of the low frequency band signal is abnormally high in comparison with the amplitude value of the high frequency band signal, it is decided to be the wind noise. Thereby, a wind noise suppressor in which when the wind is weak, a wind noise removing function consisting of a noise removing filter 7 is not operated nor is a deterioration in a sound quality at the time of no wind, can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 2B The present invention relates to a sound pickup device for a video camera having a wind noise suppression function.

BACKGROUND OF THE INVENTION In recent years, video cameras have become rapidly popular. The problem with recording with this video camera is that when shooting outdoors, the recording quality deteriorates significantly due to wind noise.

Video cameras use automatic gain control, or AGC, to control the recording level to a constant level in order to record sounds from nearby and distant objects at the same level. Therefore, if wind blows and a high level of wind noise occurs when shooting outdoors, not only will the wind noise be picked up, but the gain will be automatically lowered, significantly reducing the sensitivity to the sound from the subject. .

Therefore, research and development have been carried out on methods of suppressing this wind noise. A typical example of this method is a wind noise suppression method that utilizes the difference in frequency spectra between an audio signal and wind noise.

Figure 2 shows a sound pickup device 3-2 using this conventional technology. This shows a block diagram of.

In FIG. 2, 21 is a microphone, 22 is a noise removal filter that removes the low frequency band components of the output signal of the omnidirectional microphone 21, and 23 is an external output signal, which is the output of the microphone 21 or the output of the noise removal filter 22. A switch 24 is an output terminal for selecting output.

The operation of the sound pickup device configured as described above will be described below with reference to FIG.

In FIG. 3, 31 is a microphone 21 for inputting audio.
32 shows the waveform of the output signal of the microphone 21 when wind noise is input.

From a comparison of spectrum 31 and spectrum 32 in FIG. 3, it can be seen that the wind noise spectrum is concentrated in the low frequency band. On the other hand, it is known that a band of 300 Hz to 3 kl (z) is sufficient for transmitting and recording audio signals.

That is, even if the audio signal is recorded after removing the low frequency band components below 3001 (z), the sound quality will only be perceived as deteriorating, but sufficient clarity for practical purposes can be obtained.

Therefore, a signal with low frequency band components removed by the noise removal filter 22 is prepared, and the switch 23 allows the signal to be processed by the noise removal filter 22 when the wind is weak.
When the wind is strong, the signal processed by the noise removal filter 22 is selected and output from the output terminal 24 to the outside.

Therefore, when the wind is weak, it is possible to pick up sound with good quality, and when the wind is strong, it is possible to pick up sound with excellent clarity at the expense of some sound quality.

Problems to be Solved by the Invention However, in the configuration described in section 2, it is necessary for the photographer to judge the strength of the wind and operate the switch 23. It is difficult to operate the switch 23 during shooting, so set the switch in advance regardless of the strength of the wind.
In other words, when used indoors, the noise removal filter is usually set to off, and when used outdoors, the noise removal filter is set to on. For this reason, there has been a problem in that the sound quality is always poor and the sound is picked up in poor quality outdoors.

There was still the problem that switching errors occurred frequently.

In view of the above problems, the present invention adds a function to determine the presence or absence of wind noise from a microphone output signal, and a function to automatically operate a noise removal filter based on the determination result.
The present invention provides a sound collection device that automatically takes measures against wind noise.

Means for Solving the Problems In order to achieve this object, the sound collection device of the present invention includes a microphone, a high-pass filter that extracts the high frequency band components of the output of the microphone, and a high pass filter that extracts the high frequency band components of the output of the microphone. A low-pass filter extracts the component, a high-frequency amplitude calculation section that calculates the amplitude value of the output signal of the high-pass filter, a low-frequency amplitude calculation section that calculates the amplitude value of the output signal of the low-pass filter, and a high-frequency amplitude calculation section that calculates the output of the high-frequency amplitude calculation section. It consists of a judgment section that compares the output of the frequency amplitude calculation section, and a noise removal filter inserted between the microphone and the output terminal whose frequency characteristics are controlled by the output of the judgment section. ing.

Effect: This configuration makes it possible to determine whether the signal picked up by the microphone is an audio signal or wind noise. In the case of wind noise, the noise removal filter is automatically activated to pick up the sound with high clarity. Be able to do it.

In other words, without any special operation by the photographer, when the wind is weak the sound quality is automatically set to excellent sound quality, and when the wind is strong the sound quality is automatically set to a high clarity state with wind noise countermeasures taken at the expense of sound quality. be done.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of a sound pickup device according to an embodiment of the present invention.

In Fig. 1, 1 is a microphone, 2 is a high-pass filter that extracts the high-frequency band components of the output of the microphone 1, 3 is a low-pass filter 7 that extracts the low-frequency band components of the output of the microphone 1, and 4 is a A high-frequency amplitude calculation unit that calculates the amplitude value of the output signal of the high-pass filter 2, 5 a low-frequency amplitude calculation unit that calculates the amplitude value of the output signal of the low-pass filter 3, and 6 the output of the high-frequency amplitude calculation unit 4 and the low-frequency amplitude a determination unit 7 that determines whether the output signal of the microphone 1 is a voice signal or noise based on the output of the calculation unit 5;
is a noise removal filter inserted between the microphone 1 and the output terminal 8, which is controlled to lower the gain of the low frequency band when the determination unit 6 determines that it is noise; 8 is the output terminal.

The operation of the sound pickup device configured as described above will be explained below.

The output signal of the microphone in FIG. 3 used in the explanation of the conventional example is the same as the output signal of the microphone in the present embodiment, and FIG. 3 will also be used in the explanation of the present embodiment. In FIG. 3, 31 is the spectrum of the output signal of the microphone 1 when voice is input, and 32 is the same waveform as the output signal of the microphone 1 when wind noise is input.

As mentioned above, from the comparison of spectrum 31 and spectrum 32 in FIG. 3, it can be seen that the wind noise spectrum is concentrated in the low frequency band.

Therefore, to determine whether a signal is a voice signal or wind noise, it is sufficient to examine the frequency spectrum of the signal.

In this embodiment shown in FIG. 1, the output of the microphone 1 is
The high-pass filter 2 and low-pass filter 3 separate the signal into a high frequency band signal and a low frequency band signal. The signals in these two frequency bands are input to a high frequency amplitude calculation section 4 and a low frequency amplitude calculation section 6, and the amplitude values of the signals in each frequency band are determined. These two amplitude values are input to the determining section 6, where they are compared and it is determined whether the signal is an audio signal or wind noise. This determination unit 6 determines that it is wind noise when the amplitude value of the low frequency band signal is abnormally high compared to the amplitude value of the high frequency band signal. In other words, when the value obtained by dividing the amplitude value of the low frequency band signal by the amplitude value of the high frequency band signal is less than a preset threshold value, it is determined to be an audio signal, and when it is greater than the threshold value,
It is determined to be wind noise.

Next, this judgment signal is sent to the noise removal filter 7 to control the cutoff frequency of this filter. When the wind is weak, that is, when the determining section 6 determines that wind noise is generated a lot, the cutoff frequency is lowered to collect sound with the best sound quality, and when the wind is strong, that is, when the determining section 6 determines that wind noise is generated a lot, the cutoff frequency is lowered and the sound is collected with the best sound quality. When it is determined that the system is working, the cutoff frequency is raised and the sound quality is slightly sacrificed to obtain sound with excellent clarity.

As described above, according to this embodiment, the high-pass filter 2
The low-pass filter 3, the high-frequency amplitude calculation section 4, the low-frequency amplitude calculation section 5, and the determination section 6 make it possible to automatically detect wind noise. By operating the noise removal filter 7 based on the determination result of the detection unit, it becomes possible to activate the wind noise removal function of the noise removal filter 7 only when the wind is strong. Therefore, when the wind is weak, the wind noise removal function by the noise removal filter 7 does not work, and when there is no wind, the sound collection device of the present invention has a function of detecting wind noise, and responds to the result of this detection. By controlling the noise suppression filter, only wind noise can be effectively removed.

Furthermore, since all of these operations are performed automatically, it is possible to realize a sound collection device that is extremely easy to handle, free from operational errors, and highly effective in suppressing wind noise.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a sound collection device according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional sound collection device, and FIG. 3 is a frequency spectrum diagram of a microphone output signal. 1...Microphone, 2...High pass filter, 3...Low pass filter, 4...
High frequency amplitude calculation section, 6...Low frequency amplitude calculation section, 6...
. . . Determination unit, 7 . . . Noise removal filter, 8
...Output terminal.

Claims (1)

[Claims] a microphone, a high-pass filter for extracting a high-frequency band component of the output of the microphone, a low-pass filter for extracting a low-frequency band component of the output of the microphone, and a high-frequency amplitude calculation for calculating the amplitude value of the output signal of the high-pass filter. a low-frequency amplitude calculation section that calculates the amplitude value of the output signal of the low-pass filter; and an output of the high-frequency amplitude calculation section and an output of the low-frequency amplitude calculation section to determine whether the output signal of the microphone is an audio signal or noise. and a noise removal filter that is inserted between the microphone and the output terminal and that is controlled to lower the gain of the low frequency band when the determination unit determines that it is noise. A sound collection device characterized by: