# US 5,706,393 A · Audio signal transmission apparatus that removes input delayed using time time axis compression

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- Number: US 5,706,393 A
- Document ID: US5706393A
- Status: Granted
- Kind: A
- Application number: 08/415,618
- Filed: 1995-04-03
- Granted: 1998-01-06
- Earliest claimed: 1994-04-08
- Assignees: Matsushita Electric Industrial Co., Ltd.
- Inventors: Hiroyuki Ehara
- Web page: https://patentgrep.com/patent/US5706393A

## CPC

- G10L 25/78: Detection of presence or absence of voice signals (switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10)
- G10L 21/04: Time compression or expansion
- H04B 1/46: by voice-frequency signals; by pilot signals
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- H04B: TRANSMISSION

## Abstract

An audio signal transmission apparatus for use in a system for judging whether voice or sound is present or not to transmit only the voice presence portion of a digital audio signal which apparatus transmits data inputted earlier than the judgment time of the voice presence to thereby prevent the head of a word from being lost and dissolves the delay time caused at this time by compressing the time axis. The apparatus includes a delay circuit for storing a past audio signal data train, a time axis compression unit for compressing an audio signal taken out from the delay circuit through a switch and an audio signal inputted through a switch on a time axis, a level judgment unit for judging whether the audio signal is present or not to operate the switches, and a data conversion unit for converting the digital audio signal into parameters to be transmitted. An audio signal data train inputted earlier than the judgment time of the voice presence can be transmitted without occurrence of a delay time to thereby prevent the head of a word starting from a frictional or explosive consonant sound from being lost.

## Claims

### Claim 1

An audio signal transmission apparatus comprising:
an input terminal for receiving a digital audio signal having data frames;
level judgment means, connected to said input terminal, for detecting an audio signal level represented by the received digital audio signal for each of said data frames to generate a first control signal for a predetermined period when the detected audio signal level is changed from a level smaller than a predetermined level to a level larger than said predetermined level and to generate a second control signal when the detected audio signal level is larger than said predetermined level;
delay means, connected to said input terminal, for delaying the received digital audio signal;
time axis compression means for compressing the digital audio signal delayed by said delay means on a time axis at a constant rate to produce the compressed digital audio signal while said first control signal is present; and
data conversion means for converting the compressed digital audio signal into parameters to be transmitted when said first control signal is present and converting the received digital audio signal into parameters to be transmitted when said first control signal is absent and said second control signal is present.

### Claim 2 (depends on 1)

The audio signal transmission apparatus according to claim 1, wherein said predetermined period is substantially equal to an integral multiple of a period corresponding to one data frame of said digital audio signal.

### Claim 3 (depends on 1)

The audio signal transmission apparatus according to claim 1, wherein a delay time of said delay means is substantially equal to a period corresponding to one data frame of said digital audio signal.

### Claim 4 (depends on 3)

The audio signal transmission apparatus according to claim 3, wherein:
said predetermined period is substantially equal to a period corresponding to N data frames of said digital audio signal where N is an integer larger than 1; and
said time axis compression means compresses the digital audio signal delayed by said delay means on a time axis at a constant rate of k=N/(N+1) while said first control signal is present.