Biomedical subjects

N Thyer

Publications and source records attributed to N Thyer.

3 recordsLinked to original sources

PubMed2000

The perceptual magnet effect in Australian English vowels.

Recent research (Kuhl, 1991) has suggested that the internal structure of vowel categories is graded in terms of stimulus goodness. It has been proposed that a best instance stimulus reflects a central point or prototype, which effectively renders within-category members perceptually more similar. Discrimination experiments suggest a nonlinear relationship between acoustic and perceptual space near category centers (Iverson & Kuhl, 1995b). This phenomenon has been described as the perceptual magnet effect. The present study investigated the presence of the perceptual magnet effect in five Australian vowel categories. Australian English speakers identified, rated, and discriminated between a pool of 32 vowel stimuli that varied in F1 and F2 values. The results from Experiments 1 and 2 showed that subjects were able to judge the quality and identify of each stimulus and that a general grading of stimulus quality was reported. This was not symmetrical, and the subjects' responses varied considerably. In Experiment 3, closer control of the methodology in the discrimination task and of contextual factors influencing the test materials was exercised. Despite this, evidence of the warping of perceptual space in discrimination data was not found. In general, these results do not provide support for the existence of the perceptual magnet effect, and explanations for this finding are discussed.

Adult↗

PubMedDate not supplied

Auditory processing and phonologic disorder.

In a previous experiment, 30 children with speech disorder were categorized into three groups depending upon their surface phonologic error patterns: those whose errors reflected delayed development, those who consistently made nondevelopmental errors, and those whose realization of the same words was variable. The study reported here compared the three sub-groups' auditory processing skills with those of a group of control nonspeech-disordered children to test whether any particular group displayed evidence of auditory processing deficit. None of the speech-disordered groups performed any differently from the controls. The result is discussed in terms of the debate concerned with auditory processing as a cause of speech and language deficit.

Child↗

PubMedDate not supplied

Acoustic analysis of speech through a hearing aid: consonant-vowel ratio effects with two-channel compression amplification.

In this study, the consonant-vowel ratio (CVR) changes associated with varying the compression ratio and crossover frequency of two-channel syllabic compression amplification were examined. Consonant-vowel syllables were recorded at 60 and 75 dB SPL input levels to the hearing aid under 13 different amplification conditions: 12 compression conditions and a condition that used linear amplification in both channels. Syllables consisted of voiceless stops, fricatives, and affricates combined with the vowels /a/, /i/, and /u/. Acoustic analysis of the processed syllables indicated that the CVR was generally increased with compression, compared to linear amplification, and that the effects were greatest for amplification with compression in the high-frequency channel. In addition, higher CVRs were obtained when the crossover frequency was raised. Compression in the low-frequency channel had the least effect on CVR. As previous research has indicated that CVR may serve as a cue to the perception of some consonant sounds by people with hearing impairment, the results suggest the need for caution with the application of high-frequency channel compression until the perceptual effects are fully investigated.

Hearing Aids↗