Biomedical subjects

S G Fletcher

Publications and source records attributed to S G Fletcher.

34 records · Page 2Linked to original sources

PubMed1976

Nasalance in utterances of hearing-impaired speakers.

Instrumental comparisons of sound from the nose and mouth expressed in percent nasalance, articulation errors, and speech rate are used in this study to contrast utterances of 50 speakers with severe hearing impairment and 64 with normal hearing. Results of the study revealed that 54% of the hearing-impaired subjects had nasalance ratio scores greater than two standard deviations above the mean of the group with normal auditory acuity. No general relationship was found between the number or type of articulation errors and the nasalance scores. Rate of speaking was significantly related to the nasalance scores of the normal group but not those of the hearing-impaired group. Tonagrams displaying the variations in nasalance revealed small, 1 to 50% spike-shaped fluctuations in the displays of the utterances from both groups. Additional prolonged bursts of nasalance in excess of a 30% change in the ratio between the nasal and oral signal were common in the displays from the hearing-impaired group did not in those of the group with normal acuity. Possible sources and perceptual effects of these phenomena are discussed.

Adolescent↗

PubMed1976

"Nasalance" vs. listner judgements of nasality.

In this article, judgements of nasality from sound field recorded utterances of 23 children with repaired palatal clefts are compared with "nasalance" values derived from TONAR II analyses of parallel sound separated recordings. For the nasality judgements, the sound field recordings were presented in forward reproduced mode to 20 "naive" listeners and in backward reproduced mode to 10 naive listeners. A four-level task progression was followed in each mode of presentation: sorting the responses by "normal" or "abnormal" nasality, ranking them by severity of nasality, classifying them within five degrees of nasality, and, finally, assigning a discrete score to the magnitude of nasality perceived in each recording. Scores from the individual judges were highly variable, especially in the first listening task. They were consitently more variable when nasality was judged from backward reproduced recordings. As the listeners gained experience and as the listening tasks demanded more precision in nasality judgements, variability was reduced. Correlations computed between the nasality ratings and nasalance measurements increased and variability decreased. Highest agreement between physical and perceptual measurements was found when variability among the judges was reduced by pooling the scores and comparing the mean scores of nasality with the nasalance scores. Using this procedure, a correlation of .91 was obtained between listener judgemental scores of forward reproduced speech and nasalance scores. Under these conditions, the instrumental score could apparently account for over 80 per cent of the variability in the listener judgements of nasality. From the findings of this study, it was concluded that listeners without prior training are capable of judging nasality reliably and that nasalance scores provide a valid correlate of perceived nasality. The use of backward reprodeced recordings was questioned as a means of assessing nasality.

Acoustics↗

PubMed1975

Dynamic palatometry.

A computer-based instrumental system is described for continuous palatometry. Thin pseudopalatal plates (approximately 0.2 mm) with embedded electrodes are used to detect linguapalatal contact during speech articulation. Geometric configurations of such contacts are then derived and displayed to reveal articulatory characteristics.

Computers↗

PubMed1974