8 kbps voice transmission by SPAC

A speech Processing system named SPAC (Speech Processing system by use of AutoCorrelation function) can successfully compress or expand the speech spectrum and reduce the noise level superposed on speech signal. By employing these functions of SPAC, three types of low-bit-rate transmission system, which bit rate is 8 or 10 kbps, have been proposed. These are zero-crossing+SPAC, ADM+SPAC, and band-compression and -expansion by SPAC (compression ratio : 3). Evaluation by hearing tests is made on these sytems, zero-crossing and ADM. It is shown that ADM+SPAC with 8 kbps can transmit natural and acceptable speech.