Speech signal compression using sub-band division and sub-adaptive polynomial mapping quantization

Data compression techniques, such as image compression and speech compression, are useful in communication applications. We propose a simple speech compression algorithm using sub-band division and polynomial mapping quantization made from the piecewise linear quantization function for a voice-mail system. The voice-mail is an audio equivalent of sending letters. The main differences are that computer networks deliver the mail instead of a postman, and that electronic recording is used instead of a postman. Although speech data are stored in a semiconductor memory device, its capacity and the available network capacity are limited. Therefore, it is necessary to compress the data as much as possible. However there are two conditions to be satisfied: one is that the reconstructed data must be understood correctly. The other is that we must identify the sender. Signals with a rate of 64 kbit/sec are compressed at a ratio of about 1/13 using the proposed sub-band division and polynomial mapping quantization.