Effects of auditory anchors on perceptual judgment of hypernasality.

Abstract

Perceptual judgment of hypernasality is a common and widely accepted practice among speech-language pathologists. However, because these judgments are somewhat subjective, reliability is an issue. This study examined the effect of auditory anchors on the validity of judgments of hypernasality in both natural and acoustically manipulated speech samples. In addition, this study investigated the effectiveness of auditory anchors developed using acoustic manipulation of first-formant bandwidth to simulate speech nasality. Anchors consisted of sentences of unprocessed speech and speech that had been acoustically altered by first formant bandwidth to 150 Hz, 300 Hz, and 500 Hz. The wider the bandwidth, the greater the expected nasality. Thirty subjects were assigned one of two groups. The “Anchor” group followed a training procedure to practice rating hypernasality by listening to speech samples and using visual feedback indicating most-correct judgments. The “No Anchor” groups were exposed only to speech with varied apparent nasality. All subjects then rated both acoustically manipulated as well as unprocessed speech and rated on perceived nasality of samples. Results indicated that unprocessed samples were perceived to be most natural, and those in the 150 Hz bandwidth condition were perceived to be the least natural. Surprisingly, samples with bandwidths of 300 and 500 Hz elicited ratings that were intermediate between unprocessed speech and 150 Hz. In this study, auditory anchors did not improve rater accuracy. To conclude, the training regimen presented in this study as a means for improving speech-language pathologists' rating of hypernasal speech can be confidently ruled out for practice of future professionals.