JPH0329530A - Muting circuit - Google Patents

Abstract

PURPOSE:To reduce the generation of stimulating voice giving displeasure in audible sense when the voice is generated again after the end of muting period by decreasing the voice level just after the end of the muting period. CONSTITUTION:When the input of a mute signal is finished, a gate switching section 11 sends a signal turning off a gate from a zero cross point just after, sends a signal turning off the gate, sends a select signal to a selector section 14 simultaneously, and the selector section 14 selects the outputs a digital voice data from a bit shift section 13. Moreover, a gate section 12 outputs a voice data from the selector section 13. Then the gate switching section stops the transmission of the select signal at the succeeding zero cross point, the selector section 14 selects an input digital voice data and the gate section outputs the input digital voice data. Thus, the outputted voice signal, after the end of the mute signal, becomes a signal whose level is halved only till the succeeding zero cross point and even when a voice signal at the end of the muting period is large, the listening sense of a stimulating voice is relieved.

Description

[Detailed description of the invention]

[Field of Application in Business A] The present invention relates to a muting circuit for audio signals. [Prior Art] Fig. 4 is a block circuit diagram of a conventional muting circuit. In the figure, <10) is the zero cross detection section,
The zero-crossing point in the input digital audio data is always detected. (1)) is the gate opening/closing part, and the gate of the input digital audio data is detected at the zero-crossing point immediately after the start or end of the mute signal. ON/OF
(12) is a gate section, which receives the gate signal from the gate opening/closing section (1l) and gates the digital audio data. Figure 5 shows the signal waveform and timing diagram of this conventional example.
Figure (a) shows the output audio signal, and Figure (b) shows the a-ute signal. Next, we will explain the operation. For example, when digital audio data encoded in two's complement format is input, the point where the most significant bit data changes from "1" to "0" or from "o" to "1" is the zero crossing point. It becomes a point. The zero-crossing detection unit (lO) constantly detects this zero-crossing point. When the main user signal is input, the gate opening/closing section (1) sends out a signal to turn on the gate from the zero cross point immediately after that, and the gate section (12) masks the digital audio data and outputs it. Set all bits of audio data to ``0''. By doing this, the output audio signal will be in a silent state with a level of zero until the end of the yawing period. Then, when the mute signal ends,
The gate opening/closing section (1) sends out a signal to turn off the gate at the zero cross point immediately after that, and the gate section (12) outputs digital audio data. As a result, the waveform of the output audio signal a becomes as shown in FIG. 5(a). [Problem to be Solved by the Invention J] Since the conventional main using circuit is configured as described above, at the end of the main using period C, the sound starts from the zero cross point in the silent state, so the sound is connected smoothly. However, there was a problem in that if the audio level was high immediately after the muting period ended, the audio would sound distorted and irritating. This invention was made to solve the above-mentioned problems, and while making use of the advantages of the conventional technology, even when the sound level is high immediately after the end of the main usage period, it can be used to create a scratchy, stimulating sound. The purpose is to obtain an inaudible euting circuit.

[Means for Solving the Problems 1] The ξ-utilizing circuit of the present invention is characterized by having means for lowering the level of the output audio signal from the zero-crossing point immediately after the end of the muting period to the zero-crossing point after a certain interval. [Operation] The means for lowering the audio level in the present invention lowers the audio level for a certain period of time immediately after the end of the muting period, thereby reducing the degree to which the audio immediately after the end of the main usage sounds like a scratchy or irritating sound. It will be done.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block circuit diagram of this embodiment, in which (l3) is a bit shift unit that bit-shifts digital audio data to reduce the audio level by half, and (l4) is a block circuit diagram of the input digital audio data and the bit-shifted digital audio data. This is a selector section that switches between audio data and audio data. FIG. 2 is a signal waveform and timing diagram for this embodiment, in which (a) shows the output audio signal, (b) the mute signal, and (C) the select signal. Next, we will explain the operation. The bit shift unit (l3) converts all bit data to 1 while retaining the most significant bit data of the digital audio data.
By shifting bits to the lower level, audio data is always output with the level lowered to half that of the actual data. When a mute signal is input, the gate opening/closing unit (11) outputs a signal that turns on the gate from the zero cross point immediately after the mute signal, and the gate unit (12) outputs a signal that turns on the gate from the zero cross point immediately after the mute signal is input. Mask the data and make the output data all bits ``0''. By doing this, the audio becomes silent with a level of zero until the muting period ends. Next, when the input of the mute signal is finished, the gate opening/closing section (1
)) sends out a signal to turn off the gate from the zero cross point immediately after that, and at the same time sends out a select signal to the selector section (14), and the selector section (14) receives the digital audio from the bit shift section (13). Select and output data. Gatero (l2) is the selector part (l3
) outputs the audio data from ). Then, the gate opening/closing section (1) stops sending out the selection signal at the next zero cross point, the selector section (l4) selects the human-powered digital audio data, and the gate section outputs the input digital audio data. ．． As a result, the output audio signal becomes a signal whose level is halved only from the end of the mute signal until the next zero cross point, as shown by the solid line in Figure 2 (a), and when the main using period ends. Even when the audio signal is large, the sound is less likely to be perceived as irritating. Note that in the above embodiment, a digital signal was used as the audio signal, but the invention can be similarly applied to an analog signal. Further, the means for lowering the level of the audio signal is not limited to the bit shift section, and the rate at which the level is lowered is not limited to half. Furthermore, in the above embodiment, the level of the audio signal during the period is lowered from the zero-crossing point immediately after the end of the muting period to the next zero-crossing point, but as shown in FIG. , after the level continues to be lowered, the level may be returned to the original level from the first detected zero crossing point. [Effects of the Invention] As described above, according to the present invention, the sound level immediately after the end of the main listening period is lowered, so that when the muting period ends and the sound comes out again, it will not be audible. This has the effect of providing a main using circuit that can reduce the occurrence of irritating sounds.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of one embodiment of the present invention, '! J
Figure 2 is a signal waveform and timing diagram of this embodiment, Figure 3 is
The figure is a block circuit diagram of another embodiment of the present invention, and FIG. 4 is a block circuit diagram of a conventional main using circuit.'! J5
The figure shows the signal waveform and timing diagram of this conventional example. (10... Zero cross detection section, (1))... Gate opening/closing section, (12)... Gate section, (l3)... Bit shift section, (l4)... Selector section. In each figure, the same symbols indicate the same or equivalent parts.

Claims (1)

[Claims] (1) means for detecting a zero-crossing point of an input audio signal;
Gate opening/closing means gates the audio signal from the zero-crossing point of the audio signal immediately after the mute signal is input, and releases the gate of the audio signal from the zero-crossing point of the audio signal immediately after the mute signal ends, and the level of the input audio signal. and switching means for outputting the audio signal lowered to the predetermined level from the time when the audio signal gate is released to the zero cross point after a certain interval.