JPS60101599A - Amplitude adjustment circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplitude adjustment circuit for setting the amplitude level of an audio signal to an appropriate level.

In general, the size of a voice signal changes depending on the condition of the person making the sound, the surrounding situation, etc.

However, if you input it directly into a speech analyzer or speech recognition device, it will be too large or too small to operate at an appropriate level. For this reason, a method is used to appropriately adjust the level using an amplitude adjustment circuit. In this case, the input/output characteristics of a general amplitude adjustment circuit are as shown in FIG. 1, and the small level rises rapidly and the large level is controlled to a constant level.

FIG. 2 is a diagram for explaining an example of a control circuit for performing the above-mentioned control, where ■ is an input terminal, 2 is an amplitude attenuator, 3 is an amplifier, 4 is a level detector, and 5 is an output terminal. in,
The amplitude of the input signal from the input terminal 1 is controlled by an amplitude attenuator 2. The output of the amplitude attenuator 2 is amplified by the amplifier 3 and output to the output terminal 5, and is simultaneously applied to the level detector 4, and the amplitude attenuator 2 is controlled by the output of the level detector 4. The attenuation characteristics at this time are as shown in FIG. 3, and when the output is large, the attenuation is large and when the output is small, it is small, and as a result, the characteristics shown in FIG. 1 are obtained. However, a problem in this case is that the gain of the noise level increases in silent sections where there is no speech signal, resulting in incorrect detection of the beginning of a speech word or inability to detect a silent section in the middle of a word.

The first aspect of the present invention is to overcome the above-mentioned drawbacks of the prior art by improving the amplitude adjustment circuit for appropriately setting the level of the audio signal. This was done with the aim of resolving the issue.

The groove formation of the L-warm invention will be described below based on Examples.

FIG. 4 is an electrical block diagram for explaining one embodiment of the present invention, in which 6 is a bias circuit, 7 is a switching means, 8 is a voice section detection circuit, and the rest is the same as in FIG. 2. The same reference numerals as in FIG. 2 are given to the parts which act. Therefore, the present invention provides a gain at the noise level.
This is intended to provide an amplitude adjustment circuit that can suppress the rise in amplitude and adjust the amplitude only in the audio signal section, as shown in the figure.
It has an amplitude attenuator 2, an amplifier 3, a level detector 4, a bias circuit 6 that applies a constant bias to the silent section, and a switching means 7 that switches between the level detector output and the bias output. This method attempts to adjust the amplitude by adjusting the gain of only the audio signal using the detection signal of the detector that detects the audio section of the signal. That is, in FIG. 4, the input signal is applied to the amplitude attenuator 2 and simultaneously applied to the voice section detector 8. However, in this case, the voice section refers to the section excluding silent sections such as consonants. The amplitude attenuator 2 controls the amplitude of the input signal by the output from the switching means 7 which switches between the level detector 4 and the output of the bias circuit 6 which provides a constant bias.
In this case, the constant bias is the value where the attenuation characteristic in Figure 3 is large,
In other words, the noise level is set to a level that is not emphasized.

This switching between the level detector 4 and the bias circuit 6 is performed in synchronization with the detection signal of the voice section detector 8.

As is clear from the above explanation, according to the present invention, the amplitude of the input audio signal is adjusted only in the voice section, so that the voice section is not erroneously detected due to a noise signal, and appropriate amplitude control can be performed. can do.

[Brief explanation of drawings]

Figure 1 is an input/output characteristic diagram of a general amplitude adjustment circuit;
3 is a diagram showing an example of a general amplitude adjustment circuit, FIG. 3 is an attenuation characteristic diagram of an attenuator, and FIG. 4 is an electrical block diagram for explaining an embodiment of the present invention. . 2... Attenuator, 3... Amplifier, 4... Level detector, 6... Bias circuit, 7... Switching circuit, 8
...Voice section detection circuit.

Claims (2)

[Claims] (1) It has an amplitude attenuator that sets the level of the audio signal to an appropriate value, an amplifier connected in cascade to the amplitude attenuator, and a level detector that detects the output level of the amplifier, and the level detector The amplitude adjustment circuit controls the amplitude attenuator using the output signal of the attenuator, and includes a voice section detection means for controlling the voice section of the voice No. iiJ, and detects the level based on the voice section detection signal from the voice section detection means. Turn the output of the device on and off? ′? An amplitude adjustment circuit that adjusts the amplitude of a voice signal only in a voice section. (2) Claims characterized in that the level of the noise equalization signal is kept lower than the signal level by controlling the amplitude attenuator by changing a constant bias in the noise section and the silent section. The amplitude adjustment circuit according to item (1).