JPH04363996A - Audio processing unit - Google Patents

Abstract

PURPOSE:To process an audio signal easily without being affected with noise such as wind with simple constitution by providing a low frequency attenuation means and a control means to the processing unit. CONSTITUTION:The processing unit is provided with a low frequency attenuation means 13 attenuating a low frequency signal of an inputted audio signal and outputting the attenuated signal and a control means controlling the attenuation characteristic of the low frequency attenuation means 13 in response to the level of the low frequency signal of the inputted audio signal and the level of an intermediate frequency signal. Thus, the audio signal is easily processed without the effect of noise having a low frequency band such as wind with simple constitution without increasing the size of the unit.

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 audio.

0002

[Background Art] Conventionally, audio processing devices have been used to form audio signals by converting audio into electrical signals using a microphone or the like, and record the formed audio signals on a recording medium using a tape recorder or the like. There is a device.

In the above-mentioned audio recording device, the frequency characteristics of the audio signal amplification circuit that amplifies the audio signal generated by the microphone are often almost constant, and in this case, when the microphone is hit by wind, recording Wind noise mixes into the audio you are trying to hear, degrading the audio signal, so the microphone was equipped with a windscreen to prevent the effects of the wind.

Furthermore, since the noise generated by the wind noise described above is a low-frequency signal in terms of frequency, in recent years, frequency characteristics have been added to audio signal amplification circuits so that low frequency components can be removed from audio signals. A changeover switch is provided, and the operator operates the changeover switch when there is wind to operate the audio signal amplification circuit to remove the low frequency components of the audio signal, thereby preventing the influence of the wind. .

[0005]

However, in the case of the above-mentioned conventional apparatus, there is a problem in that the apparatus becomes large in size when the wind screen is used to prevent the influence of wind.

[0006] Furthermore, when the operator arbitrarily operates a changeover switch to operate the audio signal amplification circuit to remove the low frequency components of the audio signal to prevent the influence of wind, the operator It is very difficult to judge the presence or absence of the switch and operate the changeover switch, and there is a possibility of erroneous operation.

That is, in order to judge the degree of influence of wind noise, the operator must constantly monitor the sound collected by the microphone, which is inconvenient for the operator.

[0008] Furthermore, if the switch is operated without monitoring the audio, for example, even though wind is hitting the microphone, the switch may not be operated and the low frequency components of the audio signal must be removed. , the level of the wind sound becomes higher than the level of the sound you are trying to record, and the AGC (Auto G) in the audio signal amplification circuit
ain Controller), the level of the overall sound collected by the microphone may drop due to wind noise, or the level of the audio signal may be lowered by operating the selector switch even though there is no wind hitting the microphone. If the low frequency components are left unremoved, the low frequency components of the sound collected by the microphone will always be removed, which will impair the sound quality of the sound being recorded.

The present invention solves the above-mentioned problems and provides a voice processing device that can easily process voices without increasing the size of the device and without being affected by wind noise or other noise. The purpose is to do.

0010

[Means for Solving the Problems] The audio processing device of the present invention is a device for processing audio, which inputs an audio signal, attenuates a low frequency signal of the input audio signal, and outputs a low frequency signal. It has an attenuation means, and a control means for controlling the attenuation characteristic in the low frequency attenuation means according to the level of the low frequency signal and the level of the middle frequency signal of the input audio signal, Further, a low frequency attenuation means inputs an audio signal, attenuates a low frequency signal of the input audio signal, and outputs the low frequency signal, and a level of the low frequency signal of the input audio signal and the low frequency attenuation means. and control means for controlling the attenuation characteristics of the low frequency attenuation means in accordance with the level of the mid-range frequency signal of the audio signal outputted from the means, and the control means for controlling the attenuation characteristic in the low frequency attenuation means, and for inputting the audio signal, frequency characteristic variable means for varying and outputting the frequency characteristic of the input audio signal; It also has a frequency characteristic variable means for inputting an audio signal, varying the frequency characteristic of the input audio signal, and outputting a frequency characteristic of the input audio signal; and control means for controlling variable characteristics in the frequency characteristic variable means according to the level of the frequency component and the level of the mid-range frequency component of the audio signal output from the frequency characteristic variable means, and a frequency characteristic variable means for inputting an audio signal, varying the frequency characteristic of the inputted audio signal, and outputting the frequency characteristic; and control means for controlling.

[0011]

[Operation] According to the above configuration, it becomes possible to easily process audio without increasing the size of the device and with a simple configuration without being affected by noise in the low frequency band such as wind. .

0012

EXAMPLES The present invention will be explained below using examples of the present invention.

FIG. 1 is a diagram showing a schematic configuration of an audio recording apparatus as a first embodiment of the present invention.

In FIG. 1, 1 is a microphone for converting audio into an electrical signal, 2 is a variable filter for changing the frequency characteristics of the audio signal generated by the microphone 1, and 3 is an output from the variable filter 2. The amplifier 4 is an AGC (Auto Gain Control) that limits the level of the audio signal amplified by the amplifier 3 so that it does not exceed a predetermined level.
r), 5 is a recording unit for recording the level-limited audio signal in the AGC 4 on a recording medium such as a magnetic tape, and 6 is a band for separating low frequency components of the audio signal generated from the microphone 1. Pass filter (BPF
), 7 is a BPF for separating the middle frequency component of the audio signal generated from the microphone 1, and 8 is a BPF for separating the mid-range frequency components of the audio signal generated from the microphone 1.
An amplifier that amplifies the low frequency component signal separated by the PF 6, an amplifier 9 that amplifies the middle frequency component signal separated by the BPF 7, and 10 a low frequency component of the audio signal amplified by the amplifier 8. detect the signal of
11 is a detection circuit that outputs a detection signal; 11 is a detection circuit that detects the high frequency component of the audio signal amplified by the amplifier 9 and outputs a detection signal; 12 is a low frequency output from the detection circuit 10; A comparison circuit 13 compares the level of the detection signal of the component signal and the detection signal of the mid-range frequency component signal output from the detection circuit 11 and outputs a comparison signal; 13 is a comparison circuit output from the comparison circuit 12; This is a time constant circuit for setting an attack cover time in order to prevent changes in the frequency characteristics of the variable filter 2 controlled by the signal from becoming audible.

In FIG. 1, sound collected by a microphone 1 is converted into an electrical signal (that is, a sound signal), and is supplied to a variable filter 2 and BPFs 6 and 7.

FIGS. 2 and 3 are diagrams showing the frequency characteristics of the signal output from the microphone 1.
A in the figure indicates the frequency characteristic of the voice to be recorded, and W indicates the frequency characteristic of wind noise.

As shown in FIGS. 2 and 3, the frequency characteristics of voice are distributed around 1 kHz, except in special cases, and the frequency characteristics of wind noise are distributed in a low frequency band of 200 Hz or less. .

If there is not much difference between the wind noise level and the voice level as shown in FIG. 3, the wind noise will not be perceptually noticeable compared to the voice, but as shown in FIG. If the sound level is low compared to the wind noise level, the wind noise will be audibly noticeable compared to the sound.
Furthermore, A is usually recorded on a recording medium such as a magnetic tape.
Since the level of the audio signal is controlled by GC so that it does not exceed a predetermined level, if the wind noise level is large, the wind noise level is limited, and the audio level becomes relatively low, which affects the auditory sense. Wind noise becomes more noticeable.

Furthermore, in order to eliminate the influence of wind noise, conventional audio amplification circuits of tape recorders and the like often attenuate the signal component of wind noise by attenuating audio signals of 100 Hz or less. Alternatively, as shown in Figure 3, it is also distributed at high frequencies, so even if an audio signal of 100 Hz or less is attenuated, the high frequency components of wind noise in the frequency band of 50 to 200 Hz, for example, remain unattenuated. This will degrade the sound quality of the audio you are trying to record.

Therefore, in this embodiment, the BPF 6 in FIG. 1 having a low frequency passband indicated by L in FIG. 4 and the BPF 7 in FIG. 1 having a middle frequency passband indicated by M in FIG. A low frequency band signal and a medium frequency band signal are extracted from the signal, and an audio signal generated by the microphone 1 is supplied according to the difference in detection level of each extracted signal. By changing the signal passing characteristics of the variable filter 2, for example, by changing the amount of attenuation in the low frequency range as shown in FIG. 5, or by changing the cutoff frequency in the low range as shown in FIG.
It is configured to eliminate the influence of wind noise.

The above processing operation will be explained in detail below.

The audio signal output from the microphone 1 in FIG. 1 is supplied to BPFs 6 and 7.

In the BPF 6 of FIG.
A signal in the low frequency band indicated by L in FIG.

The detection circuit 10 detects the signal in the low frequency band extracted by the BPF 6, and a detection signal is outputted from the detection circuit 10 and supplied to the comparison circuit 12.

Furthermore, the BPF 7 in FIG. 1 extracts a signal in the middle frequency band indicated by M in FIG. The signal is amplified and supplied to the detection circuit 11.

The detection circuit 11 detects the signal in the middle frequency band extracted by the BPF 7, and a detected signal is outputted from the detection circuit 11 and supplied to the comparison circuit 12.

In the comparison circuit 12, the detection circuits 10 and 11
The level of the detection signal of the low frequency signal output from
The level of the detected signal of the mid-range frequency signal is compared, and according to the level difference, the higher the low-range detection level is than the mid-range detection level, the lower the frequency band in the variable filter 2. A comparison signal that lowers the gain of is outputted and supplied to the time constant circuit 13.

The time constant circuit 13 integrates the comparison signal outputted from the comparison circuit 12 using a capacitor or the like, and when the level of the integrated signal exceeds a predetermined threshold, the variable filter is activated in accordance with the level of the integrated signal. Continuously changing the pass characteristics of the variable filter 2 in a direction that attenuates the local frequency component, and discharging the capacitor, and also changing the pass characteristic of the variable filter 2 in a direction that attenuates the local frequency component when the capacitor is discharged. As shown in FIG. 7, the variable filter 2 changes the frequency characteristics to attenuate the wind noise signal component (W' in the figure) mixed into the audio signal. I try not to make it hard to hear.

Then, the audio signal whose wind noise signal component has been attenuated by the variable filter 2 is amplified by the amplifier 3, and the level is limited by the AGC 4 so as not to exceed a predetermined level. recorded on the recording medium.

As described above, in this embodiment, the low frequency components of the audio signal output from the microphone are adjusted according to the difference between the level of the low frequency components and the level of the middle frequency components of the audio signal. By configuring the frequency characteristics of the variable filter to be attenuated to change, when the level of the mid-range frequency component is high, the low-range frequency component is not attenuated, and when the level of the mid-range frequency component is low, the low-range frequency component is not attenuated. It is possible to attenuate the range frequency components, and to make the wind noise signal component mixed in the audio signal less noticeable perceptually.Furthermore, as shown in Figure 1, AGC is applied before recording on the recording medium.
Even if the noise level is multiplied, it is possible to prevent the level of the audio signal component to be recorded from being attenuated due to the influence of the wind noise signal component.

FIG. 8 is a diagram showing a schematic configuration of an audio recording device as a second embodiment of the present invention. Components similar to those of the first embodiment shown in FIG. 1 are designated by the same reference numerals. , and detailed explanation will be omitted.

As shown in FIG. 8, the middle frequency components in the audio signal whose frequency characteristics are not changed in the variable filter 2 are extracted from the audio signal after being amplified by the amplifier 3.
Since the signal is extracted by F7, the amplifier 9' connected to the next stage of the BPF 7 does not need a large amplification factor, so the amplifier 9' has a smaller amplification factor than the amplifier 9 shown in FIG. Therefore, the same effect as the first embodiment shown in FIG. 1 can be obtained, and the configuration can be simplified.

In both the first and second embodiments described above, the low frequency component signal and the mid frequency component signal of the audio signal output from the microphone are extracted, and both signals are extracted. It is configured to control the characteristics of a variable filter that changes the low frequency characteristics of the audio signal according to the difference in detection level, but the detection level between the low frequency component signal and the mid-high frequency component signal Alternatively, the characteristics of the variable filter may be controlled according to the difference in the detection level of the low frequency component signal, the mid frequency component signal, and the high frequency component signal. It becomes possible to obtain the same effects as in the first and second embodiments.

FIG. 9 is a diagram showing a schematic configuration of an audio recording apparatus as a third embodiment of the present invention.

In FIG. 9, reference numeral 14 denotes a variable equalizer for changing the frequency characteristics of the audio signal generated by the microphone 1, and the other configuration is the same as that of the first embodiment shown in FIG. Therefore, the same reference numerals are given and detailed explanation will be omitted.

In this embodiment, the signal is generated from the microphone 1 by the BPF 6 in FIG. 9 having a low frequency passband indicated by L in FIG. 4 and the BPF 7 in FIG. 9 having a middle frequency passband indicated by M in FIG. A signal in a low frequency band and a signal in a medium frequency band are extracted from the signal, and an audio signal generated by the microphone 1 is supplied according to the difference in detection level of each extracted signal. The influence of wind noise can be reduced by changing the frequency characteristics of the variable equalizer 14, for example, by changing the level of the low frequency component as shown in FIG. 10, or by changing the low cutoff frequency as shown in FIG. It is configured to remove.

The above processing operation will be explained in detail below.

The audio signal output from the microphone 1 in FIG. 9 is supplied to BPFs 6 and 7.

In the BPF 6 of FIG. 9, the microphone 1
A signal in the low frequency band indicated by L in FIG.

The detection circuit 10 detects the signal in the low frequency band extracted by the BPF 6 , and a detection signal is output from the detection circuit 10 and supplied to the comparison circuit 12 .

Furthermore, the BPF 7 in FIG. 9 extracts a signal in the middle frequency band indicated by M in FIG. The signal is amplified and supplied to the detection circuit 11.

The detection circuit 11 detects the intermediate frequency band signal extracted by the BPF 7 , and a detected signal is output from the detection circuit 11 and supplied to the comparison circuit 12 .

In the comparison circuit 12, the detection circuits 10 and 11
The level of the detection signal of the low frequency signal output from
The level of the detected signal of the mid-range frequency signal is compared, and according to the level difference, the higher the low-range detection level is than the mid-range detection level, the more the variable equalizer 1
A comparison signal that reduces the level of the low frequency component of the frequency characteristic at 4 is output and supplied to the time constant circuit 13.

In the time constant circuit 13, the comparison signal outputted from the comparison circuit 12 is integrated by a capacitor or the like, and when the level of the integrated signal exceeds a predetermined threshold, the variable equalizer is adjusted according to the level of the integrated signal. The frequency characteristic of the variable equalizer 14 is continuously changed in the direction of decreasing the level of the low frequency component, and the capacitor is discharged, and even when the capacitor is discharged, the frequency characteristic of the variable equalizer 14 is changed to decrease the level of the low frequency component. By continuously changing the frequency characteristics in the decreasing direction, the variable equalizer 14 changes the frequency characteristics to attenuate the wind noise signal component (W' in the figure) mixed into the audio signal as shown in FIG. This is done so that the sound does not become audibly difficult to hear.

The audio signal whose wind noise signal component has been attenuated in the variable equalizer 14 is level-limited in the AGC 4 so as not to exceed a predetermined level, and then recorded in the recording section 5 on a recording medium such as a magnetic tape. Ru.

As described above, in this embodiment, the low frequency component of the audio signal output from the microphone is adjusted according to the difference between the level of the low frequency component and the level of the middle frequency component of the audio signal. By configuring to change the frequency characteristics of the variable equalizer 14 that reduces the level,
When the level of the mid-range frequency component is high, the level of the low-range frequency component can be reduced without reducing the level of the low-range frequency component, and when the level of the mid-range frequency component is small, the level of the low-range frequency component can be reduced, and the audio signal It is possible to make the wind noise signal component mixed into the recording medium less noticeable, and as shown in Fig. 9, even if AGC is applied before recording on the recording medium, the recording will not be possible due to the influence of the wind noise signal component. This makes it possible to prevent the level of the audio signal component to be attenuated.

FIG. 12 is a diagram showing a schematic configuration of an audio recording device according to a fourth embodiment of the present invention. Components similar to those of the third embodiment shown in FIG. 9 are designated by the same reference numerals. with
Detailed explanation will be omitted.

As shown in FIG. 12, the middle frequency components in the audio signal whose frequency characteristics are not changed by the variable equalizer 14 are extracted by the BPF 7.
Since the amplifier 9' connected to the next stage of the BPF 7 does not require a large amplification factor, the amplifier 9' requires a smaller amplification factor than the amplifier 9 shown in FIG. It is possible to obtain the same effects as in the embodiment described above, and also to simplify the configuration.

In both the third and fourth embodiments described above, the low frequency component signal and the mid frequency component signal of the audio signal output from the microphone are extracted, and both signals are extracted. The variable equalizer is configured to control the frequency characteristics of a variable equalizer that changes the low frequency characteristics of the audio signal according to the difference in detection level, but it is difficult to detect the low frequency component signal and the mid-high frequency component signal. The variable equalizer is configured to control the frequency characteristics according to the difference in level or the comparison result of the detection level of each of the low frequency component signal, the middle frequency component signal, and the high frequency component signal. Also, the same effects as in the third and fourth embodiments can be obtained.

[0050]

[Effects of the Invention] As described above, according to the present invention, it is possible to easily process audio without increasing the size of the device and with a simple configuration without being affected by noise such as wind. This makes it possible to provide an audio processing device that can perform the following tasks.

[Brief explanation of the drawing]

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

FIG. 2 is a diagram showing frequency characteristics of a signal output from a microphone in the audio recording apparatus shown in FIG. 1;

3 is a diagram showing frequency characteristics of a signal output from a microphone in the audio recording apparatus shown in FIG. 1; FIG.

FIG. 4 is a diagram showing frequency characteristics of a bandpass filter in the audio recording device shown in FIG. 1;

FIG. 5 is a diagram showing frequency characteristics of a variable filter in the audio recording device shown in FIG. 1;

6 is a diagram showing another frequency characteristic of the variable filter in the audio recording device shown in FIG. 1. FIG.

7 is a diagram showing the frequency characteristics of a signal output from a variable filter in the audio recording apparatus shown in FIG. 1. FIG.

FIG. 8 is a diagram showing a schematic configuration of an audio recording device as a second embodiment of the present invention.

FIG. 9 is a diagram showing a schematic configuration of an audio recording device as a third embodiment of the present invention.

10 is a diagram showing frequency characteristics of a variable equalizer in the audio recording device shown in FIG. 9; FIG.

11 is a diagram showing another frequency characteristic of the variable equalizer in the audio recording device shown in FIG. 9; FIG.

FIG. 12 is a diagram showing a schematic configuration of an audio recording device as a fourth embodiment of the present invention.

[Explanation of symbols]

1 Microphone 2. Variable filter 3 Amplifier 4 AGC 5 Recording Department 6 Bandpass filter 7 Bandpass filter 8 Amplifier 9 Amplifier 10 Detection circuit 11 Detection circuit 12 Comparison circuit 13 Time constant circuit 14 Variable equalizer

Claims (5)

[Claims] 1. An apparatus for processing audio, comprising a low frequency attenuation means for inputting an audio signal, attenuating a low frequency signal of the input audio signal, and outputting the low frequency signal; An audio processing device comprising: control means for controlling attenuation characteristics in the low frequency attenuation means according to the level of the low frequency signal and the level of the middle frequency signal. 2. An apparatus for processing audio, comprising: inputting an audio signal, attenuating a low frequency signal of the input audio signal and outputting the low frequency attenuation means; and control means for controlling attenuation characteristics in the low frequency attenuation means according to the level of the low frequency signal and the level of the middle frequency signal of the audio signal output from the low frequency attenuation means. Characteristic voice processing device. 3. A device for processing audio, comprising: inputting an audio signal; frequency characteristic variable means for varying the frequency characteristics of the input audio signal; and a frequency characteristic variable means for outputting the frequency characteristic of the input audio signal; An audio processing device comprising: control means for controlling variable characteristics in the frequency characteristic variable means according to the level of the component and the level of the mid-range frequency component. 4. An apparatus for processing sound, comprising: inputting an audio signal; frequency characteristic varying means for varying the frequency characteristics of the inputted audio signal; and a control means for controlling variable characteristics in the frequency characteristic variable means according to the level of the component and the level of the mid-range frequency component of the audio signal output from the frequency characteristic variable means. Device. 5. An apparatus for processing audio, the apparatus comprising: inputting an audio signal, varying the frequency characteristics of the input audio signal, and outputting a frequency characteristic variable means; An audio processing device comprising: control means for controlling variable characteristics in the frequency characteristic variable means according to the distribution.