Effects of acoustical context on perceived vowel quality
Helen M. Pattison, Roy B. Gardner, Chris J. Darwin · The Journal of the Acoustical Society of America · 1986
Vowels along an /I/-/e/ continuum with added energy at a harmonic frequency near to F are embedded in sequences of tones and their phonetic quality assessed by the position of the phoneme boundary. If the sequence of tones has the same frequency as the added energy, then its contribution to vowel quality decreases as the number of tones preceding the vowel is increased, and is greater if the tone sequence continues after the vowel, indicating a greater tendency for the added tone to be perceptually segregated from the vowel. A similar effect is observed if the vowel is embedded in a sequence of tones which descends in frequency (by whole tones, or by half-harmonic steps), coinciding with the vowel at the harmonic frequency. However, if the tone sequence ascends in frequency, then the added tone does alter the perceived vowel quality, indicating that the tone sequence has not captured the embedded tone. In a further experiment a single tone at various frequencies preceded the vowel by various time intervals. The experiment showed that the difference between ascending and descending series was due to the cumulative individual effects of the two tones that immediately preceded the vowel, rather than to the configuration of the series. [Work supported by SERC.]