Comparison of Acoustical and Telephonic Speech-Signal Instantaneous Amplitude-Density Functions
Weiant Wathen‐Dunn · The Journal of the Acoustical Society of America · 1962
Recordings of speech material, read in an anechoic chamber and picked up simultaneously both by a telephone handset and by a high-quality condenser microphone, were made with a system which preserves waveform. Both signals were kept polarized. The signal from the condenser microphone is a good replica of the acoustical pressure wave, at least for the lower frequencies where the greater part of the speech energy lies; and, consequently, the statistics of the telephone signal can be compared with those of the high-quality signal to indicate the statistical transformation a given speech signal undergoes when transduced by a standard telephone transmitter. An analog-to-digital converter and a computer were used to get fine-grained histograms from which density and distribution functions of the instantaneous amplitudes of the 2 signals could be calculated, and these have been compared as to peak factor and asymmetry for a sufficiently large population, so that the statistics for English-speaking males begin to stabilize.