A speech recorder and synthesizer using ADPCM

A speech recorder and synthesizer based on adaptive differential pulse code modulation (ADPCM) is presented. The system is designed and implemented as a stand-alone unit. The unit is intended as a speech cuing subsystem to assist speech shaping for disabled individuals. Calculations show that ADPCM has a constant signal-to-noise-ratio advantage over PCM for bit rates from 20 to 50 kb/s. The ADPCM system can produce a toll-quality speech at 32 kb/s with 4-bit ADPCM samples.<>