Computer studies on parametric coding of speech spectra
James L. Flanagan, S. W. Christensen · The Journal of the Acoustical Society of America · 1980
We report a series of computer experiments aimed to increase our understanding about the sufficiency of the short-time amplitude spectrum for speech coding, and to examine how bandpass segments of the speech spectrum might be represented parametrically. For this purpose we utilize the absolute value of the short-time Fourier transform and the time-derivative of the short-time phase, evaluated at frequency intervals chosen according to auditory criteria. We analyze and digitally encode these parameters. We find that a frequency resolution corresponding to contiguous 1/6-octave bands, spanning the range 200 to 3200 Hz, is a perceptually satisfactory design, and permits digital coding of respectable quality at transmission rates in the range 20 to 16 K bits/s. We also find that a combination of subband coding and short-time spectrum coding leads to comparable results and provides added economy in processing.