A statistical analysis of third-octave speech amplitude distributions

Abstract

Amplitude distributions which probabilistically describe the level variations present in third-octave bands during speech have been obtained through the periodic sampling of the short-term rms speech envelope in each band. Representative density functions are presented for a variety of speech materials including isolated CVC syllables and nonsense sentences spoken by male and female talkers. In general, the amplitude distributions do not have simple analytic forms, although they can be described parametrically in terms of cumulative percent levels. Typically, the range of amplitudes between the 10% and 90% cumulative levels in each frequency band exceeds 40 to 50 dB. Detailed characteristics of the density functions, however, change significantly across frequency. In the low-frequency bands, the distributions are bimodal, reflecting distinct amplitude ranges for voiced and unvoiced speech segments. The distributions become unimodal and more peaked in the higher frequency channels. Comparisons of these results with previous characterizations of speech amplitude distributions [i.e., H. K. Dunn and S. D. White, J. Acoust. Soc. Am. 11, 278 (1940] are also presented. [Work supported by NIH.]