Effects of frequency shifts on the identification of vowels and words in sentences
Peter F. Assmann, Terrance M. Nearey · The Journal of the Acoustical Society of America · 2007
Studies of the effects of frequency shifts on vowel identification have shown a drop in accuracy when the spectrum envelope is shifted up or down, and when the fundamental frequency (F0) is raised or lowered. We have found an interaction between F0 and spectrum envelope shifts: Performance is better for vowels with matched shifts (both F0 and spectrum envelope shifted in the same direction) compared to mismatched shifts (F0 shifted up and spectrum envelope shifted down or vice versa). The aim of the present study was to determine the extent to which these effects persist in sentence context. The STRAIGHT vocoder was used to process a set of sentences from the HINT test using the same scale factors as in the vowel identification experiment. Word recognition scores generally followed the same pattern as vowel identification, with poorer performance for lowered F0 and raised spectrum envelope, and the lowest scores in conditions with high F0 and downward shifts in spectrum envelope, compared to the corresponding matched shifts. [Work supported by NSF and SSHRC.]