JPH07177596A - Voice processing unit - Google Patents

Abstract

PURPOSE:To obtain a desired voice signal without deteriorating sound quality by amplifying a voice level of an extracted signal of a frequency desired to be eliminated up to a predetermined level and synthesizing the amplified signal with the original voice signal. CONSTITUTION:A band pass filter (BPF) 3 extracts the same component as a noise spectrum in an output voice signal from an amplifier 2, the noise component is amplified by a voltage controlled amplifier (VCA) 4 and the amplified component is outputted to a subtractor circuit 7. Furthermore, the output voice signal from the VCA 4 is amplified by an amplifier 5, a detection circuit 6 detects an output level of the noise component and the detection circuit 6 provides an output of a control signal to control a gain of the VCA 4 depending on the level of the noise component. Moreover, the output voice signal from the amplifier 2 and the noise component from the VCA 4 are subtracted by the subtractor circuit 7, a signal processing circuit 8 applies prescribed processing to the voice signal and provides an output of the voice signal to a recording circuit 9 and a monitor 10. Then the recording circuit 9 records the voice signal onto a recording medium and the monitor 10 provides an output of sound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio processing device for processing an audio signal, and more particularly to reducing noise in the audio signal.

[0002]

2. Description of the Related Art Heretofore, as a device of this kind, a tape recorder or a camera-integrated VTR which obtains an audio signal by using a microphone and records the audio signal has been known. Then, in this type of device, in order to reduce noise in the audio signal, the audio signal from the microphone is amplified and recorded after passing through a simple filter.

[0003]

However, in such a conventional voice recording apparatus, there is noise generated from the recording / reproducing mechanism section, and this noise is generated in the apparatus integrated with the microphone. I picked it up like the audio signal I wanted to record, impairing the sound quality. Also,
As described above, in a device that is trying to remove noise by using a simple filter, it affects the audio signal itself to be recorded, which also deteriorates the sound quality.

Under such circumstances, an object of the present invention is to provide an audio processing device capable of removing noise in an audio signal to be recorded without impairing sound quality.

[0005]

SUMMARY OF THE INVENTION In order to solve the problems conventionally held and to achieve the above-mentioned object, the present invention has a sound collecting means for converting a sound wave into an audio signal and a predetermined frequency in the audio signal. Extraction means for extracting a signal, amplification means for amplifying the level of the audio signal via the extraction means to the signal level of the predetermined frequency in the sound collection means, sound signal from the sound collection means and the amplification means And a synthesizing means for synthesizing the audio signal from the.

[0006]

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

FIG. 1 is a block diagram showing the configuration of an audio recording device such as a tape recorder according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 is a microphone for picking up voice, converting it into a voice signal and outputting it, 2 is an amplifier for amplifying the voice signal from the microphone 1, 3 is a voice signal from an amplifier 2 which will be described later. A band pass filter (hereinafter BPF) for extracting noise components, 4 is a voltage controlled amplifier (hereinafter VCA) controlled by the output of the detection circuit 6, and 5 is VCA.
An amplifier for amplifying the audio signal from 4; a detection circuit 6 for detecting the output level of the audio signal from the amplifier 5; a subtraction circuit 7 for subtracting the output audio signal of the VCA 4 from the output audio signal of the amplifier 2 , 8 is a signal processing circuit for performing a predetermined process on the audio signal from the subtraction circuit 7 and converting it into a signal suitable for recording or sounding by a speaker or the like, and 9 is a sound processed by the signal processing circuit 8. The recording unit 10 for recording a signal is also a monitor such as a speaker for monitoring the sound related to the sound signal from the signal processing circuit 8.

First, the operation of this embodiment will be described.

In the configuration described above, the sound wave from the sound source and the noise including the noise from the mechanical portion of this device are picked up by the microphone 1 and output to the amplifier 2 as a sound signal. The amplifier 2 amplifies the audio signal from the microphone 1 with a predetermined gain and outputs it to the BPF 3 and the subtraction circuit 7.

The BPF 3 analyzes the frequency component (hereinafter referred to as a spectrum) of the noise generated by this device in advance, and sets a pass band in the spectrum of this noise. The same components are extracted. The noise component extracted by the BPF 3 is amplified by the VCA 4 and output to the subtraction circuit 7. The output audio signal of the VCA 4 is amplified by the amplifier 5 with a predetermined gain, and the detection circuit 5 detects the output level of this noise component. Then, the detection circuit 6 outputs a control signal for controlling the gain of the VCA 4 according to the level of the noise component, and the VCA 4 is controlled by this control signal. In other words, VCA4 is BPF
When the level of the noise component passing through 3 is large, the gain of the VCA 4 is reduced, and when the level is small, the gain is increased. Note that the VCA4 is a BPF as described later.
The level of the output signal 3 is controlled so as not to exceed a predetermined level. Output audio signal of amplifier 2 and VCA
The noise component 4 is subtracted by the subtraction circuit 7 and output to the signal processing circuit 8. The signal processing circuit 8 performs a predetermined process on the audio signal, and then outputs the audio signal to the recording circuit 9 and the monitor 10. The recording circuit 9 records the audio signal on a recording medium such as a magnetic tape, and the monitor 10 outputs the audio related to the audio signal.

Next, regarding the specific operation of this embodiment,
This will be described with reference to FIG. First, consider the silent state.
In this case, only the noise component is output from the microphone 1. In this state, the spectrum of the output signal of the amplifier 2 is observed. Here, for simplification of description, noise is A
It is assumed that the amplitude (hereinafter level) is a at a frequency of Hz. This is shown in FIG. At this time, the pass band of the BPF3 is set to AHz, and the level of the output signal of the BPF3 is a when the loss accompanying the passage of the BPF3 is l (l ≦ 1).
-L. Then, by amplifying the output signal of VCA4 by the amplifier 5, the level of the output signal of VCA4 becomes a.
The VCA 4 is controlled so that Then, the level of the output signal of the amplifier 2 becomes a and the level of the output signal of the VCA 4 becomes a, the level of the output signal of the subtraction circuit 7 becomes zero, and the noise disappears.

Next, consider the case where there is a sound source and its spectrum is BHz and its level is b. This state is shown in FIG. Even in this case, the same operation is performed except that the BHz component is present in addition to the AHz signal. Therefore, in the output signal of the amplifier 2, the signal of AHz and the level of a and the signal of BHz and the level of b are There is a signal.

On the other hand, the component of the output signal of the BPF 3, that is, the BHz signal is attenuated to a-1, and is amplified to the original level a by the VCA 4 and output. When this signal is subtracted from the output signal of the amplifier 2 shown in FIG. 2 (b) by the subtraction circuit 7, (a + b) -a = b, AHz of the noise component disappears, and only the target BHz signal is output. It

Next, the case where the present invention is most effective will be described. That is, a case will be described in which, in addition to the above-described signal shown in FIG. 2B, a signal having a spectrum AHz that is the same as the noise component AHz and a signal level of a ′ exists in the sound source. This state is shown in FIG.

In this case, in the output signal of the amplifier 2, there are signals of AHz which is a noise component, level a, AHz of the sound source, levels a'and BHz, and level b. Then, only the AHz component is extracted by BPF3, and the BPF is extracted.
In the output signal of No. 3, the signal of level a and the signal of level a ′ are mixed. In this case, the signal levels are a + a 'if the phases are the same. If the loss amount 1 of BPF3 is included in this, the signal level a + a 'is included in VCA4.
-L signal is input. Here, in the present embodiment, the VCA 4 to the amplifier 5 to the detection circuit 6 block V
When the input signal level of CA6 exceeds a certain level, VC
Since the output signal level of A4 is controlled to be constant, the VCA4 output signal should be set to a.
4, if the amplifier 5 and the detection circuit 6 are adjusted, no matter what level (including zero) the AHz component in the sound source is, V
The output signal level of CA4 becomes a.

That is, the subtracting circuit 7 always subtracts only the level a in the noise originally generated by the apparatus itself. Therefore, the level of the AHz component in the sound source becomes (a + a ')-a = a', the level of the BHz component becomes b, and the noise component disappears, and the level of the AHz component in the original sound source does not change at a '. .

As described above, according to this embodiment, when the spectrum corresponding to the noise component in the sound signal from the sound source is subtracted from the sound signal from the microphone, only the level corresponding to the level of the noise component is subtracted. Therefore, the spectrum component corresponding to the noise component in the audio signal is not attenuated. Therefore, the audio signal obtained from the microphone can be recorded and monitored without impairing the sound quality.

The difference from the conventional filter construction will be explained. In the case of attenuating only a target frequency by using a notch filter, for example, the transfer circuit has a multiplication construction, and AHz in noise is used. The transmission system is, for example, 0.01 for the components. If the level of the AHz component mixed with the AHz component existing in the sound source is a + a ', the level of the AHz component after passing through the filter is (a +
It becomes a ') × 0.01, and the AHz component in the sound source will change significantly. This is the difference in effect between the conventional configuration and the configuration of this embodiment.

Further, in the present embodiment, only the noise component of AHz was considered, but when a plurality of frequency components are obtained as noise components at the time of silence, BPF3 to detection circuit 6 in FIG. It is also possible to remove a plurality of noise components by providing a plurality of configurations and setting respective characteristics as in the above-described embodiment.

[0021]

As is apparent from the above description, according to the present invention, an audio signal having a frequency to be removed is extracted from a captured audio signal, and the level of the extracted audio signal is amplified to a predetermined level and then the original signal is extracted. Since this voice signal and the extracted voice signal are synthesized, by setting this predetermined frequency as the frequency of noise, and by setting the amplification factor of the amplifying means to amplify to the signal level of noise, ,
It is possible to obtain the desired audio signal without degrading the sound quality.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an audio recording device as an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the apparatus of FIG.

[Explanation of symbols]

 1 Microphone 3 Bandpass filter 4 Voltage control amplifier 6 Detection circuit 7 Subtraction circuit

Claims (1)

[Claims] 1. A sound collecting means for converting a sound wave into an audio signal, an extracting means for extracting a signal of a predetermined frequency in the audio signal, and a level of the audio signal passed through the extracting means, the sound collecting means. And an amplifier that amplifies to a predetermined level based on the signal level of the predetermined frequency, and a synthesizer that synthesizes the audio signal from the sound collecting unit and the audio signal from the amplifier. Audio processor.