PERCEPTUAL EVALUATIONS OF SPECTRAL AND TEMPORAL MODIFICATIONS OF DEAFSPEECH

The perceptual effect of modifying speech produced by deaf talkers was investigated to discover the changes necessary for disordered speech to be judged normal. Recordings of passages read by three deaf talkers were used as material. For the first two experiments, a three-syllabl e word was extracted from the deaf talkers' passages and from a simila r passage recorded by a hearing talker. Each of the deaf speech sample s was paired with the normal speech sample to generate various continu a that differed in the spectral and temporal modifications applied to them. Within each continuum, the individual stimuli varied in the shap e of the spectrum envelope and were produced by linear interpolation o f LPC analysis parameters between the deaf and normal speech endpoints . Results suggest that correcting the temporal component of deaf speec h alone is not enough to make it sound normal. Spectral corrections th at approximate about 70% of normal appear to be necessary for the deaf speech samples to be judged normal. A third experiment made use of a 10-syllable segment of speech in which the relative contributions of s pectral and temporal adjustments were investigated. The general conclu sion of these three experiments is that spectral adjustments are more important to perceptual judgments of normality than temporal adjustmen ts. (C) 1998 Acoustical Society of America. [S0001-4966(98)05506-4]