JPH08272377A - Noise reduction device - Google Patents

Abstract

(57) [Summary] [Purpose] A large and stable noise reduction effect is obtained.
Moreover, it is possible to provide a noise reduction device that can avoid the increase in the weight and weight of the camcorder. When the sensor 7 detects a signal having a strong correlation with the noise of the main body of the camcorder, the adaptive FIR filter 11 generates a cancellation signal based on the signal and has a sound phase opposite to that of the noise and having the same sound pressure, and the adder 15 Combines the cancellation signal with the noise signal from the built-in microphone 2. The coefficient updating unit 16 sequentially calculates and updates the coefficient of the adaptive FIR filter 11 that maximizes the noise reduction amount based on the residual signal generated as a result of the synthesis by the adder 15. By using an active method as a means for reducing the noise of the camcorder, it is possible to avoid an increase in the size and weight of the main body of the camcorder and obtain a great noise reduction effect. Since a method of reducing noise by adding a noise signal and a cancellation sound signal at the stage of an electric signal is used, a stable noise reduction effect can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise reducing device for removing mechanical noise of a camcorder main body mixed in a built-in microphone of a camcorder at a stage of an electric signal before being recorded on a tape.

[0002]

2. Description of the Related Art Conventionally, a camcorder has adopted a structure in which a microphone (hereinafter, abbreviated as "microphone") is incorporated in order to meet the demand for miniaturization.

Therefore, since the microphone is inevitably arranged near the mechanism, noise due to mechanical vibration is picked up, and the sound recorded on the tape has an extremely low S / N. .

On the other hand, noise has been reduced by a passive method such as using a rubber as a holding member so as to prevent mechanical vibration from being transmitted to the microphone and devising microphone alignment.

Such a conventional passive noise reduction method will be described below with reference to FIG. FIG. 7 is a block diagram of a camcorder to which a conventional passive noise reduction method is applied.

In this camcorder, as shown in FIG. 1, a partition plate (between the camcorder main body 21 and the built-in microphone 2 is provided so that noise 6 from a noise source (various drive motors) 1 is not transmitted to the built-in microphone 2. Plastic) 2
2 and the rubber 23 for holding the microphone are arranged, and as a device for alignment, the position where the built-in microphone 2 is installed is kept as far as possible from the noise source (various drive motors) 1.

Next, the operation of the camcorder to which the conventional passive noise reduction method is applied will be described.

When the noise source (various drive motors) 1 is activated, noise 6 is generated. Part of the generated noise 6 is transmitted through the casing of the camcorder main body 21 as vibration noise, and the other is transmitted through the air and mixed into the built-in microphone 2 as acoustic noise. At this time, acoustic noise is blocked by the partition plate 22 and the microphone holding rubber 23, so that the built-in microphone 2
The noise that reaches the partition 22 and the rubber 23 for holding the microphone are
Less than without. On the other hand, vibration noise is also attenuated in the process of propagating through the partition plate 22 and the microphone holding rubber 23, and the noise reaching the built-in microphone 2 is reduced as compared with the case where the partition plate 22 and the microphone holding rubber 23 are not provided.

On the other hand, as a means for reducing the noise radiated by the equipment, a sensor detects a signal having a strong correlation with the noise, and the signal is processed by an adaptive FIR filter into a sound having a phase opposite to that of the noise and having the same sound pressure. An active method for reducing noise by outputting it from a speaker and interfering with the noise has been proposed.

Such a conventional active noise reduction device will be described below with reference to FIG. FIG. 8 is a block diagram of a conventional noise reduction device.

As shown in FIG. 1, the conventional noise reduction device includes a sensor 7 for detecting a signal having a strong correlation with the noise 6 from the noise source 1, and an amplifier 8 connected to the output side of the sensor 7.
A low-pass filter 9 and an A / D converter 10, an adaptive FIR filter 11 that generates a cancel signal that is a sound having the same sound pressure as the noise 6 based on the output value of the A / D converter 10 , A speaker 25 for generating a sound toward the microphone 25, a D / A converter 12, a low-pass filter 13, and an amplifier connected between the adaptive FIR filter 11 and the speaker 24. 14 and an FRI filter 26 having a transfer function from the speaker 24 to the microphone 25 as a coefficient.
, A coefficient updater 16 for updating the coefficient of the adaptive FIR filter 11, an amplifier 3, a low-pass filter 17 and an A / D connected between the microphone 25 and the coefficient updater 16.
And a converter 18.

Next, the operation of the above-mentioned conventional active noise reduction device will be described.

A signal having a strong correlation with the noise 6 is detected by a sensor 7 arranged in the vicinity of the noise source 1, an amplifier 8 amplifies the signal, and a low pass filter 9 attenuates a frequency higher than a cut-off frequency. The converter 10 converts the digital signal. The converted signal is converted by the adaptive FIR filter 11 into a cancel signal having the same sound pressure and a phase opposite to that of the noise at the position where the noise is to be silenced, and then the D / A converter 1
It is converted into an analog signal by 2, attenuated by the low pass filter 13 at a frequency equal to or higher than the cutoff frequency, and amplified by the amplifier 14. The amplified cancel signal is output to the room by the speaker 24 and interferes with the noise 6. Further, the residual noise generated as a result of the interference of the noise canceling signal is input to the microphone 25 installed near the position where the noise canceling signal is to be silenced, and the amplifier 3
Is amplified by the low pass filter 17 and is attenuated by the low pass filter 17 at a frequency higher than the cutoff frequency.
8 is converted into a digital signal, and the coefficient updater 16
One of the inputs. On the other hand, the digital signal converted by the A / D converter 10 passes through the FIR filter 26 having a transfer function from the speaker 24 to the microphone 25 as a coefficient, and becomes the other input of the coefficient updater 16. The coefficient updater 16 sequentially calculates and updates the coefficient of the adaptive FIR filter 11 so that the sound pressure is minimized at the position where the sound is to be silenced. As a result, the residual signal in the microphone 25 is reduced and the noise at the position where the noise is about to be reduced is reduced.

[0014]

However, in order to further reduce the size of the camcorder, the alignment and holding structure of the built-in microphone 2 is significantly limited. It was difficult to realize the noise reduction effect. Also, sound absorbing material
When using a sound insulation material, the increase in weight has been a serious problem.

Further, in the conventional active method, since it is necessary to control the interference phenomenon in the space, if the characteristics of the speaker 24 change due to the change of the usage environment, the interference between the noise and the cancel sound is generated. Since the condition also changes, there is a problem that the noise reduction effect becomes unstable. For this reason, no example has been reported so far applied to a camcorder whose usage is not limited.

Therefore, the present invention has been made in view of the above circumstances, and provides a noise reducing device which is capable of obtaining a large and stable noise reducing effect and which can avoid an increase in size and weight of a camcorder. It is intended to be provided.

[0017]

Means for Solving the Problems The means of the present invention for achieving the above object will be described.

The noise reducing device according to the first aspect of the present invention is a noise reducing device for removing noise of the main body of a camcorder, which is mixed in a built-in microphone of the camcorder, at a stage of an electric signal before being recorded on a tape. A sensor that is installed inside the camcorder and that detects a signal that is deeply correlated with the noise, and an adaptive F that generates a cancel signal that is a sound having an opposite phase and the same sound pressure as the noise based on the detected signal.
An IR filter, an adder for synthesizing the generated cancellation signal and the noise signal from the built-in microphone, and a maximum amount of noise reduction based on a residual signal generated as a result of the synthesis by the adder. Coefficient updating means for sequentially calculating and updating the coefficients of the adaptive FIR filter is provided.

According to a second aspect of the present invention, the noise reduction device is characterized in that the sensor is an acceleration sensor for detecting motor vibration.

According to a third aspect of the present invention, there is provided the noise reduction device, wherein the sensor is a microphone for detecting motor noise.

[0021]

The operation of the present invention having the above construction will be described.

According to the noise reducing device of the first aspect of the invention, when the sensor detects a signal having a close correlation with the noise of the main body of the camcorder, the adaptive FIR filter has a phase opposite to the noise based on the detected signal. It also generates a cancellation signal that produces the same sound pressure. The adder combines the generated cancel signal and the noise signal from the built-in microphone. The coefficient updating means sequentially calculates and updates the coefficient of the adaptive FIR filter that maximizes the noise reduction amount based on the residual signal generated as a result of the synthesis by the adder. By using an active method as a means for reducing the noise of the camcorder, it is possible to avoid an increase in the size and weight of the main body of the camcorder and obtain a great noise reduction effect. Further, since it is only necessary to reduce the noise recorded on the tape, it is not necessary to reduce the noise by the interference phenomenon in the space, and the noise is reduced by adding the noise signal and the cancel sound signal at the electric signal stage. The method can be used, and thereby a stable noise reduction effect can be obtained.

According to the noise reducing device of the second aspect of the invention, the acceleration sensor detects the motor vibration that is closely related to the noise.

According to the noise reduction device of the third aspect of the invention, the microphone detects motor noise that is closely correlated with noise.

[0025]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a noise reduction device according to a first embodiment of the present invention.

As shown in the figure, the noise reduction device 100A of the present embodiment is such that a noise 6 from a noise source (various drive motors) 1 of the camcorder main body mixed in a built-in microphone 2 of the camcorder, an amplifier 3, a recording device. The sensor 7 is to be removed at a stage of an electric signal before being recorded on the tape 5 via the sensor 7, which is mounted inside the camcorder and detects a signal deeply correlated with the noise 6 from the noise source 1; An amplifier 8 for amplifying the detection signal of, a low pass filter 9 for attenuating a frequency equal to or higher than a cutoff frequency from the amplified sensor signal, an A / D converter 10 for converting a signal passed through the low pass filter into a digital signal, Adaptive FIR filter 11 that generates a cancellation signal that has a phase opposite to that of noise mixed in the built-in microphone 2 and has the same sound pressure.
A D / A converter 12 for converting the output signal of the adaptive FIR filter 11 into an analog signal; and an adaptive FIR filter 1
A low-pass filter 13 for attenuating frequencies above the cut-off frequency from the analog signal 1; an amplifier 14 for amplifying a signal passing through the low-pass filter 13; and an adaptive FI
The adder 15 for synthesizing the cancel signal from the R filter 11 and the noise signal from the built-in microphone 2, and the sensor 7
A coefficient updater 16 that updates the coefficient of the adaptive FIR filter 11 based on the signal obtained from the adder 15 and the signal obtained from the adder 15, and a low-pass filter 17 that attenuates the output signal of the adder 15 above the cutoff frequency. , And an A / D converter 18 for converting the signal that has passed through the low-pass filter 17 into a digital signal and inputting it to the coefficient updater 16.

Next, the operation of this embodiment will be described.

When the noise source (various drive motors) 1 is activated, noise 6 is generated. Part of the generated noise 6 is transmitted through the casing of the camcorder as vibration noise, and the other is transmitted in the air and mixed into the built-in microphone 2.
On the other hand, a signal having a strong correlation with the noise 6 is detected by the sensor 7 arranged in the vicinity of the noise source 1, the signal is amplified by the amplifier 8, the frequency above the cutoff frequency is attenuated by the low pass filter 9, and the A / D The converter 10 converts the digital signal. The converted signal is converted by the adaptive FIR filter 11 into a cancellation signal that has a sound of the same sound pressure and a phase opposite to that of the noise signal mixed in the built-in microphone 2, and then converted into an analog signal by the D / A converter 12. The low-pass filter 13 attenuates the cut-off frequency or more, and the amplifier 14 amplifies the cut-off frequency. The amplified signal is combined with the output signal of the built-in microphone 2 amplified by the amplifier 3 by the adder 15. Further, the residual signal generated as a result of combining the output signal of the built-in microphone 2 and the cancel signal in the adder 15 is attenuated by the low-pass filter 17 at a frequency equal to or higher than the cutoff frequency, and converted into a digital signal by the A / D converter 18. And becomes one input of the coefficient updater 16. Further, the noise signal from the sensor 7 converted by the A / D converter 10 becomes the other input of the coefficient updater 16. The coefficient updater 16 correlates the residual signal and the noise signal, and sequentially calculates and updates the coefficient of the adaptive FIR filter 11 so that the signal component having the correlation with the noise signal in the residual signal is minimized. As a result, the noise component in the residual signal is reduced, and the noise recorded on the tape 5 via the recording device 4 is reduced.

FIG. 2 is a block diagram showing a noise reducing device according to the second embodiment of the present invention.

The noise reduction device 100B of this embodiment is the first
In addition to the configuration of the embodiment of FIG. 3, the adder 15 connected between the amplifier 14 and the recording device 4 is replaced by the adaptive FIR filter 11
Connected to the D / A converter 12 and connected to the input side of the adder 15 by connecting the low-pass filter 17 and the A / D converter 18, which were connected to the output side of the adder 15, to the output of the amplifier 3. The signal is input to the adder 15 via the low-pass filter 17 and the A / D converter 18.

Next, the operation of this embodiment will be described.

When the noise source (various drive motors) 1 is activated, noise 6 is generated. Part of the generated noise 6 is transmitted through the casing of the camcorder as vibration noise, and is transmitted in the other air and mixed into the built-in microphone 2 as acoustic noise.
On the other hand, a signal having a strong correlation with the noise 6 is detected by the sensor 7 arranged in the vicinity of the noise source 1, the signal is amplified by the amplifier 8, the frequency above the cutoff frequency is attenuated by the low pass filter 9, and the A / D The converter 10 converts the digital signal. The converted signal is converted by the adaptive FIR filter 11 into a cancel signal which has a phase opposite to that of the noise signal mixed in the built-in microphone 2 and has the same sound pressure, and is input to the adder 15. On the other hand, the output of the built-in microphone 2 is amplified by the amplifier 3, attenuated by the low-pass filter 17 at a frequency equal to or higher than the cutoff frequency, and then the A / D converter 1
It is converted into a digital signal at 8, becomes the other input of the adder 15, and is combined with the cancel signal. further,
The residual signal generated as a result of combining the output signal of the built-in microphone 2 and the cancel signal is one input of the coefficient updater 16. Further, the digital signal from the sensor 7 converted by the A / D converter 10 becomes the other input of the coefficient updater 16. The coefficient updater 16 correlates the residual signal and the noise signal, and sequentially calculates and updates the coefficient of the adaptive FIR filter 11 so that the signal component having the correlation with the noise signal in the residual signal is minimized. As a result, the noise component in the residual signal is reduced, the residual signal is converted into an analog signal by the D / A converter 12, attenuated at a frequency higher than the cutoff frequency by the low-pass filter 13, amplified by the amplifier 14, and recorded. Noise is removed from the signal recorded on the tape 5 via the device 4, and the same effect as in the first embodiment is obtained.

FIG. 3 is a block diagram showing a noise reducing device according to a third embodiment of the present invention.

The noise reduction device 100C of this embodiment is the first
The configuration is the same as that of the first embodiment except that the acceleration sensor 19 is used instead of the sensor 7 of the first embodiment. In the noise reduction operation of the present embodiment, the acceleration sensor 19 causes the motor vibration 2 which has a strong correlation with the noise from the noise source 1.
7 is detected. Thereby, when the noise source 1 is mainly vibration of the motor, the noise can be effectively reduced.

FIG. 4 is a block diagram of a noise reduction device according to the fourth embodiment of the present invention.

The noise reduction device 100D of this embodiment has the first
The configuration is similar to that of the first embodiment except that the microphone 20 is used instead of the sensor 7 of the above embodiment. In the noise reduction operation of this embodiment, the microphone 2
0 is a motor noise 28 that is closely correlated with the noise from the noise source 1.
To detect. This makes it possible to effectively reduce noise when the noise source 1 is mainly motor noise.

FIG. 5 is a block diagram of a noise reduction device according to the fifth embodiment of the present invention.

The noise reduction device 100E of this embodiment is the second
The configuration is the same as that of the second embodiment except that the acceleration sensor 19 is used instead of the sensor 7 of the second embodiment. In the noise reduction operation of the present embodiment, the acceleration sensor 19 causes the motor vibration 2 which has a strong correlation with the noise from the noise source 1.
7 is detected. This makes it possible to effectively reduce noise when the noise source is mainly motor vibration.

FIG. 6 is a block diagram of a noise reduction device according to the sixth embodiment of the present invention.

The noise reduction device 100F of this embodiment is the second
The configuration is the same as that of the second embodiment except that the microphone 20 is used instead of the sensor 7 of the above embodiment. In the noise reduction operation of the present embodiment, the microphone 20 causes the motor noise 2 which has a strong correlation with the noise from the noise source 1.
8 is detected. This makes it possible to effectively reduce noise when the noise source is mainly motor noise.

According to each of the above-mentioned embodiments, the following many excellent effects can be obtained. (1) Since the active method is used to reduce the noise of the camcorder, the noise reducing effect can be achieved regardless of the alignment of the built-in microphone 2 and the restriction of the holding structure, and the further miniaturization of the camcorder body can be achieved. We can adapt to your request. Furthermore, since no sound absorbing material or sound insulating material is used, an increase in weight can be prevented. (2) Since the noise of the camcorder can be actively reduced at the signal stage, a speaker as an actuator and an FIR filter, which are required when actively trying to reduce the noise in space, are not required, and the system Can be further miniaturized. Further, since the speaker as the actuator is not used, the problem of the characteristic change of the speaker due to the change of use environment can be avoided, and a more stable noise reduction effect can be realized.

[0043]

According to the present invention described in detail above, the following effects can be obtained.

According to the first aspect of the present invention, the active method for removing the noise of the main body of the camcorder at the stage of the electric signal before being recorded on the tape is used to reduce the noise of the camcorder. Further, it is possible to provide a noise reduction device which can obtain a stable noise reduction effect and can avoid the increase in size and weight of the camcorder.

According to the second aspect of the present invention, the acceleration sensor for detecting the motor vibration is used as the sensor for detecting the signal having a strong correlation with the noise. Therefore, when the noise source is mainly the motor vibration, the noise is effectively generated. Can be reduced.

According to the third aspect of the present invention, by using the microphone for detecting the motor noise as the sensor for detecting the signal having a strong correlation with the noise, the noise is effectively reduced when the noise source is mainly the motor noise. It can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram showing a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram showing a sixth embodiment of the present invention.

FIG. 7 is a configuration diagram of a camcorder for explaining a conventional passive noise reduction method.

FIG. 8 is a configuration diagram of a noise reduction device for explaining a conventional active noise reduction method.

[Explanation of symbols]

 1 Noise Source (Various Driving Motors) 2 Built-in Microphone 4 Recording Device 5 Tape 6 Noise 7 Sensor 11 Adaptive FIR Filter 15 Adder 16 Coefficient Updater 19 Acceleration Sensor 20 Microphone 27 Motor Vibration 28 Motor Noise 100A to 100F Noise Reduction Device

Claims (3)

[Claims] 1. A noise reducing device for removing noise of a camcorder main body mixed in a built-in microphone of the camcorder at a stage of an electric signal before being recorded on a tape, the noise reducing device being installed inside the camcorder and correlating with the noise. Sensor for detecting a deep signal of the noise, an adaptive FIR filter for generating a cancel signal which becomes a sound having an anti-phase and the same sound pressure as the noise based on the detected signal, the generated cancel signal and the built-in microphone. An adder that combines a noise signal and the adaptive FI that maximizes the noise reduction amount based on the residual signal generated as a result of the combination by the adder.
A noise reducing device comprising: a coefficient updating unit that sequentially calculates and updates the coefficient of the R filter. 2. The noise reduction device according to claim 1, wherein the sensor is an acceleration sensor that detects motor vibration. 3. The noise reduction device according to claim 1, wherein the sensor is a microphone that detects motor noise.