Computer synthesis of speech by concatenation of formant-coded words

Speech signals can be described in terms of the resonances of the vocal tract. These resonances, or formants, change at rates comparable to the motions of the vocal tract. They therefore can be sampled and quantized to low bit-rates, and hence constitute an economical form for digital storage of speech information. Formant coding also permits flexible arrangement of speech elements into various contexts. This report describes a computer technique for synthesizing continuous messages by concatenating formant data for word-length utterances. The stored data for the synthesis corresponds to a bit-rate of 533 b/s. A Honeywell DDP-516 computer is used to experimentally evaluate a voice response system. In an initial application, the system is used to synthesize 7-digit telephone numbers. To assess the synthesis an interactive dialing experiment, also conducted by the computer, is described. The results show the synthesized numbers to be comparable in communicative effectiveness to naturally spoken digits.