Message Context and Speech Frequency-Weighting for Intelligibility
J. M. Pickett · The Journal of the Acoustical Society of America · 1960
A message from a small set of known speech messages can be transmitted over a much narrower band of frequencies than can a message from a much larger set. The present experiment is designed to measure this relation to a limited extent and to determine whether or not there are radical shifts in the importance of different regions of the speech spectrum with shifts in the size of the message set. Transmission of speech messages was measured under various band-pass filter conditions in the presence of a random noise having a spectrum approximately parallel to the long-time rms spectrum of speech. Three classes of speech context were examined: (1) CVC nonsense syllables constructed from 24 consonants and 14 vowels; (2) English monosyllabic words chosen from a set of 256 PB Words known to the listeners; and (3) words chosen from sets of 2 known words drawn from the 256-word set of (2). The results show no radical changes in the importance of different speech frequency regions over the three types of context. Implications are discussed for calculating a frequency-weighted index of intelligibility such as Articulation Index.