JP7770883B2 - IMAGING DEVICE, CONTROL METHOD, AND PROGRAM - Google Patents

Description

The present invention relates to an imaging device that can reduce noise.

Conventionally, a process for reducing lens drive noise is known that uses a noise reference microphone installed inside the camera housing in addition to a main microphone for recording external audio. Patent Document 1 discloses a method for reducing lens drive noise by iteratively estimating the impulse response of the transfer system of the main microphone from the noise reference microphone so that the result is minimized.

Japanese Patent Application Publication No. 6-253387

However, in addition to lens drive noise, the noise reference microphone is contaminated with noise generated by factors other than lens drive, such as self-noise such as electrical noise from the microphone and leakage of external sound. Additionally, the external sound picked up by the main microphone may contain sound in the same frequency band as the lens drive noise. In this case, if subtraction processing is performed using the noise reference microphone on the external sound picked up by the main microphone without taking into account the volume of that external sound, there is a risk that the signal from the main microphone will be reduced excessively.

The purpose of this invention is to prevent excessive noise reduction.

The present invention is an imaging device comprising: an external audio microphone that acquires external audio of the imaging device; a noise reference microphone that acquires drive noise of a drive unit of the imaging device or an external device connected to the imaging device; a noise calculation means that calculates an audio signal of the drive noise from a signal acquired by the noise reference microphone; an update means that stores the audio signal related to the external audio acquired by the external audio microphone and updates the stored audio signal related to the external audio when it is determined that the audio signal related to the external audio should be updated based on the signal acquired by the noise reference microphone; and a reduction means that performs processing to reduce the drive noise from the audio signal acquired by the external audio microphone based on the audio signal related to the external audio stored in the update means and the audio signal of the drive noise calculated by the noise calculation means, wherein the update means stores an average value of the audio signal acquired by the external audio microphone as the audio signal related to the external audio, and when it is determined that the audio signal related to the external audio should be updated, updates the stored audio signal related to the external audio with the average value of the stored audio signal related to the external audio and the audio signal input from the external audio microphone.

This invention makes it possible to prevent excessive noise reduction.

FIG. 1 is a block diagram of an imaging device according to a first embodiment. FIG. 2 is a block diagram of an audio processing unit and a sound collection unit according to the first embodiment. 4 is a flowchart of an audio processing unit according to the first embodiment. FIG. 6 is a diagram showing changes in the influence of acquired external environmental sound spectra in the first embodiment.

Embodiments of the present invention will be described below with reference to the drawings. Note that the following embodiments do not limit the present invention, and not all of the combinations of features described in the present embodiments are necessarily essential to the solution of the present invention. Note that the same components will be denoted by the same reference numerals in the following descriptions.

[First embodiment]
FIG. 1 is a block diagram showing an example of the configuration of an image capturing apparatus 100 which is an example of an audio processing apparatus according to the present invention.

The imaging device 100 consists of a lens unit 101, a lens control unit 102, an imaging unit 103, an image processing unit 104, a control unit 105, an operation unit 106, a display/playback unit 107, a recording unit 108, an audio processing unit 200, and an audio pickup unit 300.

The lens unit 101 performs operations such as autofocus and zooming based on signals from the lens control unit 102. The lens unit 101 may be configured to be detachable from the image capture device 100. In this embodiment, the lens unit 101 is described as being connected to the image capture device 100. The imaging unit 103 captures an optical image of the subject using an imaging element such as a CMOS sensor, and outputs a digitized image signal to the image processing unit 104. The image processing unit 104 adjusts the image quality of the image signal input from the imaging unit 103 and outputs the result. The control unit 105 is composed of a processor or the like, and sends control signals to each block of the image capture device 100. The operation unit 106 inputs user commands to start and stop capture, or capture settings, using a touch panel, dial, or the like. The display/playback unit 107 displays captured images and videos, or plays audio signals accompanying the videos. The recording unit 108 records captured images and videos.

The audio processing unit 200 and audio collection unit 300 will be described in detail using Figure 2.

<Description of Audio Processing Unit 200>
The audio processing unit 200 comprises an A/D conversion unit 201, a waveform extraction unit 202, a time-frequency conversion unit 203, a noise detection unit 204, a noise ratio calculation unit 205, a noise calculation unit 206, an external environmental sound update unit 207, a noise reduction unit 208, an audio correction unit 209, and a frequency-time conversion unit 210.

The A/D conversion unit 201 samples the analog signals from multiple microphones input from the sound collection unit 300 at the same time and converts them into digital signals. Although it is represented as a single block in Figure 2, it has the same number of A/D converters as the number of input channels from the sound collection unit 300. The converted digital microphone signals are output to the waveform extraction unit 202.

The waveform extraction unit 202 extracts the digital audio signal input from the A/D conversion unit 201 to a predetermined length for each channel, performs windowing processing, and outputs the extracted signal to the time-frequency conversion unit 203. The series of processes performed by the waveform extraction unit 202 is, for example, half-overlap processing used in general audio processing. In this embodiment, the waveform extraction unit 202 extracts 1024 samples while shifting the time every 512 samples, performs windowing processing using a sine window or Hann window, and outputs the audio signal. Thereafter, while filming is being performed, signal processing is performed in units of the above number of samples (hereinafter referred to as frames).

The time-frequency conversion unit 203 converts the audio signal input from the waveform extraction unit 202 from a time-domain audio signal to a frequency-domain audio spectrum using processing such as a Fourier transform. The audio spectrum generated from the audio signal input from the external audio microphone 301 is output to the external environmental sound update unit 207 and the noise reduction unit 208. Hereinafter, the audio to be picked up by the external audio microphone 301 is referred to as external audio or environmental sound. On the other hand, the noise reference sound spectrum, which is the audio spectrum generated from the audio signal input from the noise reference microphone 302, is output to the noise detection unit 204, noise ratio calculation unit 205, and noise calculation unit 206.

The noise detection unit 204 performs noise detection based on the noise reference sound spectrum input from the time-frequency conversion unit 203. Then, the noise detection unit 204 determines whether noise has been detected for each frame of the input noise reference sound spectrum. In this embodiment, the noise detection unit 204 detects long-term noise that continues for a certain period of time and is generated by the operation of a driving unit such as the lens unit 101, which is a noise source, and short-term noise that is generated by the start or end of the operation of the driving unit.

The noise detection unit 204 also detects a background noise spectrum based on the noise reference sound spectrum. In this embodiment, the background noise is constantly present noise, such as electronic noise from a microphone or white noise. Here, the background noise spectrum in this embodiment is calculated, for example, by averaging, over a certain period of time, the noise reference sound spectra of frames in which long-term noise and short-term noise are not detected.

The noise detection unit 204 may also perform other noise detection processes. For example, the noise detection unit 204 generates a frame by averaging the noise reference sound spectrum for a certain period (predetermined period) input before the frame in which noise is detected, and calculates the average value of the difference in the audio spectrum between this frame and the frame in which noise is detected. The noise detection unit 204 then detects noise based on whether the calculated average value exceeds a predetermined threshold. The noise detection unit 204 may also set multiple predetermined thresholds for each type of noise to detect the type of noise. The noise detection unit 204 may also use only the audio spectrum in a predetermined frequency band when detecting noise. The results detected by the noise detection unit 204 are output to the noise ratio calculation unit 205 and the noise calculation unit 206.

The noise ratio calculation unit 205 calculates the noise ratio using the noise reference sound spectrum of a frame in which noise was detected by the noise detection unit 204 and the background noise spectrum. In this embodiment, the noise ratio is calculated as the average value of the absolute value for each frequency band of the noise reference sound spectrum of a frame in which noise was detected by the noise detection unit 204 divided by the background noise spectrum corresponding to each frequency band. Note that the calculation of the noise ratio may be limited to using only the noise reference sound spectrum and background noise spectrum of a specified frequency band. The calculated noise ratio is output to the external environmental sound update unit 207.

The noise calculation unit 206 calculates the noise component spectrum contained in the signal from the noise reference microphone 302 by subtracting the background noise spectrum from the noise reference sound spectrum input from the noise detection unit 204. The noise component is the audio signal of noise contained in the audio signal. The noise calculation unit 206 performs correction to bring the noise component of the audio signal input from the noise reference microphone closer to the noise component contained in the audio signal input from the external audio microphone 301. Here, the noise calculation unit 206 is provided with a correction coefficient table for this correction, and obtains the corrected noise spectrum by multiplying the correction coefficient according to the noise component spectrum of the audio signal input from the noise reference microphone. The noise calculation unit 206 outputs the corrected noise spectrum to the noise reduction unit 208.

On the other hand, the external environmental sound update unit 207 has a storage unit (not shown) that stores the external environmental sound spectrum, and updates the stored external environmental sound spectrum as appropriate. The external environmental sound spectrum is obtained by converting an audio signal picked up by an external audio microphone into an audio spectrum. Since the external environmental sound spectrum becomes an audio signal that is recorded as a moving image, it is desirable that it does not contain noise such as lens driving noise. In this embodiment, in order to reduce the influence of lens driving noise on the external environmental sound spectrum, the external environmental sound spectrum is updated as shown in Equation 1 when the noise ratio calculated by the noise ratio calculation unit 205 in each processed frame is less than a predetermined threshold.
[Formula 1] S' _Senv (ω, t)=(S _Senv (ω, t)*α+|S _mic (ω, t)|)/(α+1)

Here, S _mic (ω, t) is the audio spectrum (external audio spectrum) of the audio signal input from the external audio microphone 301, and S _Senv (ω, t) is the external environmental sound spectrum. ω is the frequency, t is the processing frame, and α is a given coefficient. S' _Senv (ω, t) is the new external environmental sound spectrum after updating. In this way, the new external environmental sound spectrum after updating is a weighted average of the external environmental sound spectrum. Note that at t = 0, i.e., at the start of the noise reduction process, the initial value S _Senv (ω, 0) of the external environmental sound spectrum may be set to |S _mic (ω, 0)|. Alternatively, the initial value S _Senv (ω, 0) of the external environmental sound spectrum may use a pre-calculated average value of background noise such as background noise of the external audio microphone 301.

In Equation 1, the influence that the external audio spectrum of the previous frame has on the next frame at the current processing frame t is 1/(α+1). For example, when α=1, as shown in Figure 4, the influence of a given frame is halved with each frame. In this way, the influence of the previous frame on a given frame is stronger. This improves the ability of the recorded audio to follow changes in the external audio.

Note that if the noise ratio calculated by the noise ratio calculation unit 205 is equal to or greater than a predetermined threshold, this means that the audio signal input from the external audio microphone 301 contains a large amount of noise components, and therefore the external environmental sound update unit 207 does not update the external environmental sound spectrum.

The noise reduction unit 208 reduces noise from the external audio spectrum input from the time-frequency conversion unit 203 using the corrected noise component spectrum input from the noise calculation unit 206, generating a noise-reduced audio spectrum. The noise reduction unit 208 uses, for example, a Wiener filter as noise reduction means.

The audio correction unit 209 compares, for each frequency band, the audio spectrum input from the noise reduction unit 208 with the external environmental sound spectrum updated by the external environmental sound update unit 207. In bands where the audio spectrum input from the noise reduction unit 208 is smaller than the external environmental sound spectrum, there is a high possibility that frequency signals that should originally be included in the environmental sound have been excessively reduced. Therefore, in this embodiment, the audio correction unit 209 corrects the audio spectrum in the frequency band of the audio spectrum input from the noise reduction unit 208 using the following Equation 2.
[Formula 2] S' _S (ω, t) = (|S _S (ω, t) | + | S' _env (ω, t) |)/2*phas (S _S (ω, t))

Here, S _S (ω, t) is the audio spectrum input from the noise reduction unit 208, and S' _S (ω, t) is the audio spectrum after corrected noise reduction. phas(N) is a function for extracting the phase component of N (i.e., a function that sets the amplitude of each frequency component to 1). This process corrects (suppresses) excessive noise reduction, thereby suppressing deterioration in sound quality. Note that no correction is made to bands in which the audio spectrum input from the noise reduction unit 208 is equal to or larger than the external environmental sound spectrum.

The audio correction unit 209 outputs the audio spectrum to the frequency-time transform unit 210 regardless of whether correction processing has been performed.

The frequency-time transform unit 210 converts the audio spectrum input from the audio correction unit 209 into a time-domain waveform signal using processing such as an inverse Fourier transform. In this embodiment, the frequency-time transform unit 210 outputs the audio spectrum while adding frames using half overlap.

The output signal is recorded in the recording unit 108 together with the image signal from the image processing unit 104.

<Explanation of sound pickup unit 300>
The sound collection unit 300 comprises an external sound microphone 301 and a noise reference microphone 302 .

The external audio microphone 301 consists of two microphones and is installed to mainly capture the audio of the subject. In this embodiment, the two microphones capture audio corresponding to the audio signals of the Rch and Lch of stereo audio.

The noise reference microphone 302 is installed so that it can mainly capture driving noise inside the camera housing. For example, the noise reference microphone 302 is installed without an opening to the outside and is shielded by an exterior to prevent external sound from being input. The noise reference microphone is also installed near the external sound microphone 301 to detect noise that is closer to the noise input to the external sound microphone 301. Alternatively, the noise reference microphone may be installed near the noise source to capture noise more accurately.

The functions of each component described above reduce lens drive noise in accordance with the volume of the external audio input to the external audio microphone, preventing excessive noise reduction and minimizing deterioration in sound quality after noise reduction.

Figure 3 is a flowchart of audio processing in this embodiment. The processing of this flowchart is executed when the start of video recording is triggered. The following processing is realized by a control unit, such as a processor, included in the image capture device 100 controlling each unit of the image capture device 100, such as the audio processing unit 200 and sound collection unit 300. The control unit also realizes the processing of this flowchart by expanding software recorded in the image capture device 100 into memory and executing it.

In step S101, the waveform extraction unit 202 extracts a waveform from the digital signal output by the A/D conversion unit 201. The extracted signal is output to the time-frequency conversion unit 203.

In step S102, a fast Fourier transform (FFT) is performed on the digital signal input to the time-frequency conversion unit 203. The signal obtained by FFT processing of the signal from the external audio microphone 301 is output to the external environmental sound update unit 207 and the noise reduction unit 208, and the signal obtained by FFT processing of the signal from the noise reference microphone 302 is output to the noise detection unit 204, noise ratio calculation unit 205, and noise calculation unit 206.

In step S103, the noise detection unit 204 performs noise detection processing. Here, a background noise spectrum is calculated from frames in which noise is not detected, and is output together with the noise detection results to the noise ratio calculation unit 205 and noise calculation unit 206.

In step S104, the noise ratio calculation unit 205 performs a noise ratio calculation process. Here, the noise ratio is calculated using the noise reference sound spectrum and background noise spectrum of the frame in which noise was detected by the noise detection unit 204. Then, in step S105, it is determined whether the noise ratio is less than a predetermined threshold. If the noise ratio is less than the predetermined threshold, the process of step S106 is performed, and the external environmental sound update unit 207 updates the external environmental sound spectrum according to Equation 1. Note that, in this embodiment, the process of step S106 is performed when the noise ratio is less than the predetermined threshold, but the process of step S106 may also be performed when the noise ratio is equal to or less than the predetermined threshold.

In step S107, the noise component spectrum contained in the noise reference microphone signal is multiplied by a correction coefficient corresponding to the noise component spectrum of the noise reference microphone signal to calculate a corrected noise spectrum. Here, the pre-correction noise component spectrum is calculated in the noise calculation unit 206 by subtracting the background noise spectrum from the speech spectrum of the noise reference signal for the frame in which noise was detected by the noise detection unit 204. The calculated corrected noise spectrum is output to the noise reduction unit 208.

In step S108, the noise reduction unit 208 performs processing to reduce noise components contained in the audio signal input from the external audio microphone 301. Here, noise is reduced from the external audio spectrum calculated in step S102 using the corrected noise component spectrum calculated in step S107, and a noise-reduced audio spectrum is generated. In step S108, a Wiener filter, for example, is used as the noise reduction means. Note that the noise reduction means in step S108 may also be waveform subtraction in the frequency domain, for example.

In step S109, the noise-reduced audio spectrum is compared for each frequency band with the external environmental sound spectrum updated by the external environmental sound update unit 207. In frequency bands where the noise-reduced audio spectrum is smaller, the noise-reduced audio spectrum is corrected in step S110. In this embodiment, Equation 2 is used for this correction. Note that the noise-reduced audio spectrum is output to the frequency-time transform unit 210 regardless of whether it has been corrected in step S110.

In step S111, an inverse fast Fourier transform (IFFT) is performed on the audio spectrum input to the frequency-time transform unit 210. The converted signals are sequentially output to the recording unit 108 and recorded together with the image (moving image).

Then, the processing of each step from step S101 to step S111 is repeated until it is determined in step S112 that filming has ended. Filming is determined to have ended when, for example, the user performs an operation to end video recording.

By performing the processing control described above, lens drive noise is reduced in accordance with the volume of the external audio input to the external audio microphone, preventing excessive noise reduction and minimizing deterioration in sound quality after noise reduction.

The external environmental sound update unit 207 may perform the update based on the gain of the audio signal acquired by the noise reference microphone, rather than the noise ratio. This is because if the audio signal acquired by the noise reference microphone is sufficiently large, it can be determined that there is a high possibility that the audio signal contains drive noise.

In this embodiment, correction is performed by the audio correction unit 209 after noise reduction processing by the noise reduction unit 208 (steps S109 and S110), but processing may be performed using other methods. For example, in step S108, the noise reduction unit 208 may perform noise reduction processing in advance using the external environmental sound spectrum as the lower limit value for noise reduction, thereby omitting the processing by the audio correction unit 209 and steps S109 and S110.

In addition, the correction processing in the audio correction unit 209 may perform further noise reduction processing if the degree of noise reduction in the noise reduction unit 208 is low.

In this embodiment, the recording medium of the recording unit 108 is, for example, a semiconductor memory such as an SD card or a CFExpress card.

The imaging device 100 may further include a data compression unit to compress the image and video data being recorded.

In this embodiment, the drive noise is lens drive noise, but noise generated by other drive units on the image capture device body may also be reduced in a similar manner.

In this embodiment, each of the components constituting the audio processing unit 200, except for the A/D conversion unit 201, may be processed by a program using a CPU. Furthermore, each of the components constituting the audio processing unit 200, except for the A/D conversion unit 201, may be processed by hardware, such as a DSP, a dedicated LSI, or other electronic circuitry.

In this embodiment, the noise detection unit 204 performs noise detection based on a signal from the noise reference microphone 302, but it may also obtain control information from the drive unit, which is the source of the noise, and perform noise detection based on that information. For example, it may obtain a control signal for driving the lens from the lens control unit 102 and perform noise detection. The drive information may include, for example, the drive speed, drive direction, and position of the drive unit of the drive unit. The drive information may also be, for example, instruction information from the lens control unit to instruct the lens unit to start or end lens drive. Alternatively, the drive information may be internal information used by the lens control unit to determine whether to drive the lens, such as detection of an out-of-focus state or an in-focus state. A signal from the external audio microphone 301 may also be used.

The noise calculation unit 206 may perform different noise estimation processes depending on the type of noise detected by the noise detection unit 204.

In this embodiment, the noise calculation unit 206 is provided with a correction coefficient table in advance, but it may also be configured to calculate the correction coefficient table sequentially. For example, it may be configured to calculate and update an appropriate correction coefficient table based on the signal from the external audio microphone 301 and the signal from the noise reference microphone 302.

In this embodiment, the external environmental sound update unit 207 compares the noise ratio calculated by the noise ratio calculation unit 205 with a threshold value, but this threshold value may be specified in advance as an appropriate value based on the results of an auditory test or the like, or may be calculated sequentially. For example, an appropriate threshold value may be calculated and updated based on the signal from the external audio microphone 301 and the signal from the noise reference microphone 302.

In this embodiment, the noise reduction unit 208 uses a Wiener filter, but other methods may also be used. For example, the noise reduction unit 208 may use spectral subtraction, or may perform waveform subtraction in the time domain. Furthermore, it may be configured to perform processing to further reduce the volume level of signals in specific frequency bins with volume levels below a predetermined threshold. Furthermore, the noise reduction unit 208 may perform different noise reduction processing depending on the type of noise detected by the noise detection unit 204, or may select a correction coefficient table depending on the noise type. Furthermore, these processes and correction coefficient tables may be switched depending on the type of lens.

In this embodiment, the external audio microphone 301 is two microphones (stereo microphones), but processing can be performed in the same way even if the number of channels is different, such as monaural, surround, or Ambisonics.

In this embodiment, the audio processing unit 200 only performs noise reduction processing for simplicity, but it may also perform other processing. For example, it may be configured to perform spectral correction processing such as equalization to make the audio easier to hear, or processing to emphasize the stereo effect of the audio being played back. It may also be configured to perform encoding using various audio codecs such as MP3 and AAC.

In this embodiment, the noise reference microphone 302 consists of one microphone, but more microphones may be provided. Furthermore, part of the noise reference microphone 302 may be configured to be attached to the lens side. Furthermore, part or all of the noise reference microphone 302 may be vibration sensors that detect vibrations of objects, rather than microphones that capture vibrations in the air.

Furthermore, although the noise reference microphone 302 is described as being installed near the external audio microphone 301 or near the noise source, the installation location does not matter as long as noise can be acquired that can be used to estimate the noise components input to the external audio microphone 301.

Claims (10)

An imaging device,
an external sound microphone for acquiring external sound from the imaging device;
a noise reference microphone for acquiring driving noise from a driving unit of the imaging device or an external device connected to the imaging device;
a noise calculation means for calculating an audio signal of the driving noise from a signal acquired by the noise reference microphone;
an updating means for storing an audio signal relating to the external audio acquired by the external audio microphone, and updating the stored audio signal relating to the external audio when it is determined to update the audio signal relating to the external audio based on the signal acquired by the noise reference microphone;
a reduction unit that performs processing to reduce the drive noise from the audio signal acquired by the external audio microphone based on the audio signal related to the external audio stored in the update unit and the audio signal of the drive noise calculated by the noise calculation unit ,
The updating means stores an average value of the audio signal acquired by the external audio microphone as the audio signal related to the external audio, and when it determines to update the audio signal related to the external audio, updates the stored audio signal related to the external audio with the average value of the stored audio signal related to the external audio and the audio signal input from the external audio microphone . The imaging device described in claim 1, characterized in that the reduction means includes a noise reduction unit that reduces the drive noise from the audio signal acquired by the external audio microphone based on the audio signal of the drive noise calculated by the noise calculation means, and a correction unit that corrects the audio signal output from the noise reduction unit based on the stored audio signal related to the external audio. The imaging device described in claim 2, characterized in that the correction unit performs correction so as to increase the volume of frequency bands of the audio signal output from the noise reduction unit that are quieter than the stored audio signal related to the external audio. The imaging device described in claim 3, characterized in that the correction unit does not correct frequency bands of the audio signal output from the noise reduction unit that have the same volume as the stored audio signal related to the external audio or that have a volume higher than the stored audio signal related to the external audio. a noise detection means for detecting the driving noise and background noise from the signal acquired by the noise reference microphone;
a noise ratio calculation means for calculating a ratio between the value of the driving noise detected by the noise detection means and the value of the background noise;
and
The photographing device according to any one of claims 1 to 4 , characterized in that the update means updates the stored audio signal related to the external audio when the ratio calculated by the noise ratio calculation means is less than a threshold value. 6. The imaging apparatus according to claim 5 , wherein the noise ratio calculation means calculates a ratio between a predetermined frequency band of the driving noise and the predetermined frequency band of the background noise. The photographing device according to any one of claims 1 to 4, characterized in that the update means determines whether to update the stored audio signal related to the external audio based on a gain of the signal acquired by the noise reference microphone. a conversion means for converting the signal from the external audio microphone from a time domain signal to a frequency domain signal to output an external environmental sound spectrum, and for converting the signal from the noise reference microphone from a time domain signal to a frequency domain signal to output a noise reference sound spectrum,
the noise calculation means calculates a noise component spectrum of the driving noise from the noise reference sound spectrum from the conversion means;
8. The imaging device according to claim 1, wherein the reduction means reduces the drive noise from the external environmental sound spectrum from the conversion means based on the noise component spectrum, and outputs an audio spectrum in which the drive noise has been reduced. an external audio microphone for picking up external audio from the imaging device;
a noise reference microphone that acquires driving noise from a driving unit of the image capturing device or from an external device connected to the image capturing device,
a noise calculation step of calculating an audio signal of the driving noise from the signal acquired by the noise reference microphone;
an updating step of storing an audio signal related to the external audio acquired by the external audio microphone, and updating the stored audio signal related to the external audio when it is determined to update the audio signal related to the external audio based on the signal acquired by the noise reference microphone;
a reduction step of reducing the drive noise from the audio signal acquired by the external audio microphone based on the audio signal related to the external audio stored in the update step and the audio signal of the drive noise calculated in the noise calculation step ,
The update step is a control method characterized in that the average value of the audio signal acquired by the external audio microphone is stored as the audio signal related to the external audio, and when it is determined that the audio signal related to the external audio should be updated, the stored audio signal related to the external audio is updated with the average value of the stored audio signal related to the external audio and the audio signal input from the external audio microphone . an external audio microphone for picking up external audio from the imaging device;
a noise reference microphone that acquires driving noise from a driving unit of the imaging device or from an external device connected to the imaging device, the computer of the imaging device executing a control method, the control method comprising:
a noise calculation step of calculating an audio signal of the driving noise from the signal acquired by the noise reference microphone;
an updating step of storing an audio signal related to the external audio acquired by the external audio microphone, and updating the stored audio signal related to the external audio when it is determined to update the audio signal related to the external audio based on the signal acquired by the noise reference microphone;
a reduction step of reducing the drive noise from the audio signal acquired by the external audio microphone based on the audio signal related to the external audio stored in the update step and the audio signal of the drive noise calculated in the noise calculation step ,
The update step is a program characterized in that it stores an average value of the audio signal acquired by the external audio microphone as an audio signal related to the external audio, and when it is determined that the audio signal related to the external audio should be updated, it updates the stored audio signal related to the external audio with the average value of the stored audio signal related to the external audio and the audio signal input from the external audio microphone .