Spectral tilt versus formant frequency in static and dynamic vowels

Abstract

The relative importance of gross (e.g., spectral tilt) versus detailed (e.g., formant peak frequencies) for speech perception is an enduring question of substantial importance in understanding performance of both impaired and unimpaired listeners [cf. Kiefte, J. Acoust. Soc. Am. (submitted)]. In this study, subjects were presented with steady-state stimuli varying perceptually between [i] and [u] for which spectral tilt and formant frequencies were fully crossed. Results show an effect for both tilt and formants indicating some perceptual importance for both in the identification of statically specified vowels. However, this result does not appear to extend to more natural sounding stimuli with dynamic formants. For example, there was no effect for spectral tilt in a similar experiment using diphthongs ranging from [ai] to [au]. One hypothesis for this difference is that the F2 of front vowels is masked by F1 when combined with sharply falling spectral tilt and that this effect is mitigated in dynamic or naturally produced vowels. Results are also presented which compare the perception of these continua with similar stimuli in which F2 is absent as well as with dichotically presented stimuli in which F1 and F2 are heard in different ears. [Work supported by NIDCD DC04072.]