JPH07115697A - Voice reproducing device - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a voice clearness degree by changing an output voice level and a frequency characteristic in a voice reproducing device even in environment where at a dark noise level is changed. CONSTITUTION:A voice signal is from a receiting equipment 10 is given to a high-pass filter 11 and only a high-pass component is picked-up. A speaker 15 which can reproduce voice and detect the unclear noise level is provided and a noise signal obtained by the speaker 15 is inputted to a dark noise level detecting means 13 with a low-pass filter 16.When the dark noise level detecting means 13 detects that the noise level is high, an automatic gain control circuit 12 increases the gain of the voice signal of the high-pass filter 11. Therefore, the sound pressure of the speaker is automatically increased and the clearness degree of voice is not deteriorated even if the operation sound of an air conditioner inside a house or the noise of a vehicle, etc., is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice reproducing device which outputs a voice by improving the intelligibility of a target sound even in the presence of background noise.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing the structure of a typical conventional audio reproducing apparatus. In the figure, a sound signal of a radio broadcast or the like received by the receiver 1 is adjusted in volume by a built-in volume 2 and power-amplified by an amplifier 3. The output of the amplifier 3 is given to the speaker 4 and converted into voice.

In the audio reproducing device having such a structure,
Background noise may be constantly changing in the vicinity of the listener. When the background noise becomes large, the intelligibility of the voice decreases, so that the listener himself tried to improve the intelligibility by adjusting the volume 2 to increase the reproduction level.

[0004]

However, in such a structure, there is a problem that the listener must constantly adjust the volume 2 due to the change of the background noise level, and the operation is very troublesome. .

The present invention has been made in view of such conventional problems. Even when the background noise level is changed and the voice is difficult to hear, the speaker is used for both the background noise detection and the voice reproduction. An object of the present invention is to realize an audio reproducing device that outputs an audio signal with high clarity.

[0006]

According to a first aspect of the present invention, a high-pass filter for extracting only a voice component of a frequency band to be reproduced from a voice signal of a sound source, and reproducing the voice signal, A speaker that detects background noise, a low-pass filter that extracts low-frequency components of the background noise detected by the speaker, and the output signal of the low-pass filter are input to detect the background noise level. Then, the background noise level detection means for generating a control signal corresponding to this and the level of the output signal of the high-pass filter corresponding to the noise level from the background noise level detection means are controlled, and an audio signal is given to the speaker. An automatic gain control circuit,
It is characterized by including.

According to a second aspect of the present invention, a high-pass filter for extracting only a voice component of a frequency band to be reproduced from a voice signal of a sound source, and a speaker for reproducing the voice signal and detecting background noise. Then, the low-pass filter that extracts the low-frequency component of the background noise detected by the speaker and the output signal of the low-pass filter are input, and the background noise level is detected to respond to this. A background noise level detecting means for generating a control signal, and a voice for giving a voice signal to a speaker by controlling a specific band level in the output signal of the high-pass filter corresponding to the noise level from the background noise level detecting means. Characteristic correction means,
It is characterized by including.

[0008]

According to the invention of claim 1 of the present application having such a feature, when the sound signal is output from the sound source, the high-pass filter extracts only the sound component of the frequency band to be reproduced. When the speaker reproduces the audio signal and detects the background noise, the low-pass filter extracts the low-frequency component and supplies it to the background noise level detecting means. The automatic gain control circuit controls the level of the output signal of the high-pass filter in accordance with the noise level from the background noise level detecting means, and gives a voice signal to the speaker. In this way, even in a place where the background noise is large, it is possible to listen to the sound with high clarity from the speaker.

According to the invention of claim 2 of the present application, when the sound signal is output from the sound source, the high-pass filter extracts only the sound component in the frequency band to be reproduced. When the speaker reproduces the audio signal and detects the background noise, the low-pass filter extracts the low-frequency component and supplies it to the background noise level detecting means. The voice characteristic correction means controls the level of a specific band in the output signal of the high-pass filter in accordance with the noise level from the background noise level detection means, and gives a voice signal to the speaker. In this way, it is possible to select a sound that is easily heard by the human ear and increase the reproduction level automatically.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An audio reproducing apparatus according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the overall configuration of a sound reproducing device including a radio receiver. In this figure, the receiver 10 is used as a sound signal generation source.
Shall be provided. The receiver 10 receives a radio broadcast, and the selected and detected audio signal is given to the high-pass filter 11. The high-pass filter 11 is a filter that blocks low-frequency components that are often included in background noise, and passes audio signals in the middle and high frequencies. Graph A in FIG. 2 is a filtering characteristic diagram of the high-pass filter 11.

The output of the high-pass filter 11 is given to the automatic gain control circuit 12. The automatic gain control circuit 12 is a circuit that changes the gain or amplification factor of an input audio signal in accordance with a control signal of the background noise level detecting means 13 described later. That is, when the automatic gain control circuit 12 includes a preamplifier, when the output of the background noise level detection means 13 is high, the automatic gain control circuit 1
2 increases the amplification factor and holds it at a constant value when the output is low.

The output of the automatic gain control circuit 12 is the amplifier 14
Given to. The amplifier 14 is a circuit for power-amplifying an input audio signal, and its output is given to the speaker 15. The speaker 15 is, for example, a speaker having a magnet and a moving coil in a magnetic circuit. The speaker 15 converts a voice current applied to the voice coil into a voice through a diaphragm, and at the same time, generates a sound pressure such as background noise applied to the diaphragm. , Shall be converted into an electric signal through the moving coil.

The signal induced in the voice coil of the speaker 15 is given to the low-pass filter 16. The low-pass filter 16 is a filter that allows low-frequency components, which are often included in background noise, to pass through and blocks mid-range and high-range audio signals. The graph B in FIG. 2 shows the filtering characteristic of the low-pass filter 16. The place where the audio reproducing device is used varies depending on its type, but here, the target is audio that is viewed indoors such as radio and TV. Therefore, when an air conditioner (air conditioner) is operated indoors or a car passes by in the vicinity, 200H
Sound with a low frequency of z or less is generated.

The output of the low-pass filter 16 is given to the background noise level detecting means 13. Background noise level detection means 13
Is a circuit that detects the background noise level at the place where the audio reproduction device is installed, detects the output level of the low-pass filter 16 at regular intervals, and automatically obtains a control signal corresponding to the detected level. Output to the control circuit 12.

The operation of the audio reproducing apparatus of the first embodiment constructed as above will be described. Radio broadcasting receiver 1
When received at 0, the selected audio signal is sent to the high frequency filter 1
1 and the frequency components below 200 Hz are removed. Then, this audio signal is used as the automatic gain control circuit 12
Entered in.

Generally, the background noise level constantly changes at the listening position. For example, when listening indoors, when a car passes outside the house or when an air conditioner or the like is used indoors, the noise level in the low frequency band becomes large. Generally, when the masked sound is lower than the masked sound, the masking effect becomes large. Therefore, when the noise level in the low frequency band becomes large, the voice becomes less clear because of the influence of the low frequency noise.

FIG. 3 is a characteristic diagram showing the relationship between the noise level and the intelligibility of voice. The numerical value of the curve indicated by the solid line indicates the sound pressure level of external noise. When the audio information of the sound pressure level shown on the horizontal axis is output, the clarity that can be discriminated by the viewer is shown on the vertical axis. For example, when the external noise is 53 dB and the sound with the sound pressure of 40 dB is output, the clarity that the viewer can correctly identify is about 15%. Therefore, in order to increase the intelligibility of the voice to about 80% under the same external noise, the sound pressure of the voice must be increased to about 50 dB.

Now, when the background noise level around becomes high,
The diaphragm of the speaker 15 vibrates in this noise frequency band, and induced electromotive force is generated in the voice coil. This signal is given to the low-pass filter 16 and, for example, as shown in FIG.
The following components are extracted. Most of the external noise described above is low-frequency noise, so only this low-frequency signal needs to be extracted. It should be noted that although sound is also output from the speaker 15, this component is blocked by the low-pass filter 16.

The signal level from the low-pass filter 16 is detected by the background noise level detecting means 13. The background noise level detection means 13 generates a control signal for increasing the amplification factor to the automatic gain control circuit 12 when the input signal becomes large. or,
When the background noise level increases and then changes to a low level again, a process of returning the amplification factor of the automatic gain control circuit 12 to the initially set value is performed.

Here, when the audio signal from the receiver 10 is reproduced as it is, the audio signal also contains a low frequency component. Therefore, when this audio signal is directly increased by the automatic gain control circuit 12, the speaker The background noise level detected at 15 also increases. Therefore, the high-pass filter 11 extracts only the high-frequency component of the audio signal, thereby eliminating the influence of the audio signal on the background noise level. In this embodiment, as shown in FIG. 2, the cutoff frequency is set to the low-pass filter 16
At around 100 Hz, and the high-pass filter 11 at around 200 Hz. The audio signal controlled to have an appropriate level by the automatic gain control circuit 12 is amplified by the amplifier 14 and output from the speaker 15. In this case, since the S / N value of the voice is improved, the clarity of information is increased.

Next, an audio reproducing apparatus according to the second embodiment of the present invention will be described with reference to FIG. In FIG. 4, the same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 4, the audio signal received by the receiver 10 is transmitted through the high-pass filter 11 to the audio characteristic correction means 17
Given to.

When the background noise level is high, the voice characteristic correction means 17 is a circuit which increases the level of the voice band around 300 Hz to 3 KHz and corrects the frequency characteristic so that the voice band is emphasized. When the background noise level decreases, the voice characteristic correcting means 17 restores the initially set frequency characteristic, and adjusts it so that the change in the frequency characteristic in terms of hearing does not increase. The output of the audio characteristic correction means 17 is applied to the amplifier 14 and power amplified as in the first embodiment, and audio is output from the speaker 15.

In the audio reproducing apparatus configured as above, when a radio broadcast is received by the receiver 10, the audio signal is input to the high frequency filter 11 to remove the frequency component of 200 Hz or less, for example. Then, this audio signal is input to the audio characteristic correction means 17. When the background noise level at the listening position increases, the background noise level detecting means 13 gives a control signal for increasing the amplification factor to the voice characteristic correcting means 17.

When the level of the background noise is sufficiently low, the voice characteristic correction means 17 amplifies the voice signal with an amplification factor or gain such that the frequency characteristic becomes flat as shown by the characteristic G0 in FIG. Further, when the background noise level becomes high, the voice characteristic correcting means 17 makes the characteristics G1 to G in FIG. 5 corresponding to the background noise level.
As shown by 3, the amplification factor in the frequency band 300 Hz to 3 KHz is gradually increased.

The audio signal thus corrected to an appropriate frequency characteristic by the audio characteristic correcting means 17 is amplified by the amplifier 14 and reproduced by the speaker 15. In this way, the sound level in the frequency band with high auditory characteristics is increased, and the intelligibility can be improved. By finely dividing and varying the frequency characteristic of the voice according to the level of the background noise level, it is possible to control the finer frequency characteristic and further improve the voice intelligibility.

The first and second embodiments have been described with respect to the case of receiving a radio broadcast, but the same effect can be obtained when a voice signal of a television broadcast, a video, a CD or the like is reproduced.
In the second embodiment, the correction of the frequency characteristic by the voice characteristic correcting means 17 is controlled so as to emphasize the human voice band.
Arbitrary correction that emphasizes the high frequency characteristics of noise may be performed according to the frequency characteristics of background noise. Further, it is possible to obtain a great effect by combining the automatic gain control circuit and the voice characteristic correction means.

[0027]

As described above, according to the first aspect of the present invention, the background noise level detecting means and the automatic gain control circuit are provided in the audio reproducing device, so that the background noise of low frequency is present in the place where the viewer is. When occurs, the reproduction level of the audio signal of the sound source can be automatically increased. Therefore, regardless of the noise level, the effect of improving the intelligibility of voice can be obtained. Also, a microphone for background noise detection is not required.

Further, according to the invention of claim 2 of the present application, when the background noise level detecting means and the audio characteristic correcting means are provided in the audio reproducing apparatus, when a low frequency background noise is generated in the place where the viewer is present. In addition, it is possible to automatically increase the reproduction level by selecting a sound that is easily heard by the human ear. Therefore, regardless of the noise level, the effect of improving the intelligibility of voice can be obtained. Also, a microphone for background noise detection is not required.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an audio reproducing device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing cutoff frequencies of a low-pass filter and a high-pass filter used in the audio reproducing device according to the present embodiment.

FIG. 3 is a characteristic diagram showing a relationship between a noise level and a sound pressure level of voice, and the intelligibility of sound.

FIG. 4 is a block diagram showing a configuration of an audio reproducing device according to a second embodiment of the present invention.

FIG. 5 is a frequency characteristic diagram of an audio characteristic correcting means used in the audio reproducing apparatus according to the second embodiment.

FIG. 6 is a block diagram showing a configuration example of a conventional audio reproducing device.

[Explanation of symbols]

 10 receiver 11 high-pass filter 12 automatic gain control circuit 13 background noise level detection means 14 amplifier 15 speaker 16 low-pass filter 17 voice characteristic correction means

Claims (2)

[Claims] 1. A high-pass filter for extracting only a voice component of a frequency band to be reproduced from a voice signal of a sound source, a speaker for reproducing a voice signal and detecting background noise, and a speaker detected by the speaker. A low-pass filter that extracts low-frequency components of the background noise, and an output signal of the low-pass filter that is input to detect the background noise level and generate a control signal corresponding thereto. And a noise level detection means, and an automatic gain control circuit for controlling the level of the output signal of the high-pass filter in accordance with the noise level from the background noise level detection means, and giving an audio signal to the speaker. An audio playback device characterized by the above. 2. A high-pass filter that extracts only a voice component of a frequency band to be reproduced from a voice signal of a sound source, a speaker that reproduces a voice signal and detects background noise, and a speaker detected by the speaker. A low-pass filter that extracts low-frequency components of the background noise, and an output signal of the low-pass filter that is input to detect the background noise level and generate a control signal corresponding thereto. Noise level detection means, and voice characteristic correction means for controlling a specific band level of the output signal of the high-pass filter corresponding to the noise level from the background noise level detection means and giving an audio signal to the speaker. An audio reproducing apparatus comprising: