Difference limens for formant frequencies of steady-state and consonant-bounded vowels

Abstract

Difference limens of formant frequencies were measured for two steady-state vowels and the same vowels in symmetric stop-consonant contexts. The stimuli were generated using a computer-programmed synthesizer and the formant frequency parameters were held constant or adjusted to symmetric cubic functions of the time difference from the temporal center of the syllable. The difference limens (DL) for the time-varying consonant-vowel-consonant (CVC) stimuli were found to be significantly larger than those for the steady-state vowels, sometimes exceeding 10% of F1 or F2. In some cases the DL for the second formant is found to be larger in the direction of expected formant-shift due to consonantal coarticulation than in the reverse direction. The difference in DL values in and out of context has, at least partially, an auditory origin. Additionally, the phonetic decoding of the CVC stimuli may introduce information loss from auditory short-term memory. Implications for speech coding applications are discussed. [Supported in part by NICHD Grant HD-01994.]