Speech Bandwidth Compression through Spectrum Selection

PB word and sentence intelligibility tests were conducted with unfiltered speech and with speech filtered (1) by a 100–7000 cps bandpass filter, (2) by a 100–1600 cps bandpass filter, (3) by a 500 2000 cps bandpass filter, (4) by a 1000–2500 cps bandpass filter, and (5) by various configurations of one, two, or three bandpass filters, each 500 cps wide. The positions of the center frequencies of the bandpass filters 500 cps wide were systematically varied during the tests. If we use constant speech intelligibility as our criterion, the results indicate that the total “effective” bandwidth required for the best multiple pass band system is less than that required for the best contiguous pass band systems by a factor of 2. Also, a feature of the signal resulting from this multiple sampling in the frequency domain is that it sounds “natural” and the identity of a talker's voice appears to be maintained.