Biomedical subjects

Robert L Sherbecoe

Publications and source records attributed to Robert L Sherbecoe.

4 recordsLinked to original sources

PubMed2004

Supplementary formulas and tables for calculating and interconverting speech recognition scores in transformed arcsine units.

Formulas that convert speech recognition scores, in percent or proportions, into units based on the arcsine transform have been described previously. This report reviews that work and presents various supplementary equations and tables for calculating and interconverting the proposed units. The relative merits of these data and their application to scores from closed-set tests are also discussed.

Humans↗

PubMed2003

Audibility-index predictions of normal-hearing and hearing-impaired listeners' performance on the connected speech test.

OBJECTIVE: In a previous study (Sherbecoe & Studebaker, 2002), we derived a frequency-importance function and a transfer function for the audio compact disc version of the Connected Speech Test (CST). The current investigation evaluated the validity of these audibility-index (AI) functions based on how well they predicted data from four published studies that presented the CST to normal-hearing and hearing-impaired subjects. DESIGN: AI values were calculated for the test conditions received by 78 normal-hearing and 72 hearing-impaired subjects from the selected studies. The observed CST scores and AI values for these conditions/subjects were then plotted and the dispersion of the data compared to the expected range based on critical differences. The AI values for the conditions/subjects were also converted into expected CST scores and subtracted from their corresponding observed scores to determine the distribution of the resulting difference scores and the relationship between the difference scores and subject age. RESULTS: Good predictions were obtained for normal-hearing subjects who had been tested under audio-only conditions but not those who had received audiovisual tests. The expected scores for the latter subjects were too low when the AI accounted only for audibility and too high when it included the correction for visual cues from ANSI S3.5-1997. All of the hearing-impaired subjects had been tested under audio-only conditions. In their case, the mean difference between the observed and the expected scores was comparable with the audio-only mean for the normal-hearing subjects when the AI included corrections for speech level distortion and hearing loss desensitization. However, the hearing-impaired subject data had greater variability. The predictions for these subjects also decreased in accuracy when subject age increased beyond 70 yr despite the application of an AI correction for age. CONCLUSIONS: The results of this study suggest that the AI functions derived for the CST satisfactorily predict the scores of normal-hearing subjects when they listen in speech babble under audio-only conditions but not when they receive visual cues. To obtain accurate predictions for the audiovisual form of the CST, it will be necessary to develop new ANSI-style AI correction equations for visual cues or new AI functions based on audiovisual test scores. If the current AI functions are used to predict the scores of hearing-impaired listeners tested under audio-only conditions, the AI should include corrections for the effects of speech level and hearing loss. A correction for subject age also could be applied, if it seems appropriate to do so. In either case, however, the predictions are still likely to be less accurate than the predictions for normal-hearing subjects. This may be because speech recognition deficits in people with hearing loss are not due solely to diminished audibility. Hearing-impaired subjects, particularly if they are elderly, also may be more susceptible to masking effects or other factors not accounted for by the AI.

Adolescent↗

PubMed2002

Audibility-index functions for the connected speech test.

OBJECTIVE: A study was performed to derive a frequency importance function (FIF), a performance-intensity funcTIon (PIF), and a transfer function (TF) for the audio compact disc version of the Connected Speech Test (CST). DESIGN: CST passages were masked with talker-spectrum-matched (TSM) noise and presented to two groups of normal-hearing adult subjects. One group (N = 48) listened through a wideband filter, seven low-pass filters, and eight high-pass filters at six signal-to-noise (S/N) ratios. The other group (N = 12) listened through just the wideband filter at 12 S/N ratios. The FIF was based on the data for the first group while the PIF was based on the data for the second group. The results of both groups were used to determine the TF between CST scores and audibility-index (AI) values. RESULTS: The FIF, in 1/3-octave bands, is a bimodal curve with a minor peak at 500 Hz, a major peak at 1600 to 2000 Hz, and a midpoint of 1619 Hz. The PIF in TSM noise and the TF are both asymmetric S-shaped curves; their respective slopes are 12%/dB and 11%/0.0333 AI. CONCLUSIONS: Comparisons between these results and the findings of other studies reconfirm that different speech materials have different AI functions. The FIF for the CST overlaps 1/3-octave band functions for continuous discourse and average speech but does not have the same shape as those functions. The TF indicates that CST passages are generally more intelligible than isolated monosyllabic words (NU6 lists) and somewhat less intelligible than continuous discourse. The former result is probably due at least partly to the effects of context whereas the latter result may be due primarily to how clearly the talkers pronounced the speech materials.

Adolescent↗

PubMed2002

Intensity-importance functions for bandlimited monosyllabic words.

A study was carried out to determine the relative importance to speech intelligibility of different intensities within the speech dynamic range. The functions that were derived are analogous to previous descriptions of the relative importance of different frequencies and are referred to here as intensity-importance functions (IIFs). They were obtained as follows. Sharply filtered bands of speech (NU6 monosyllabic words) were mixed with filtered noise and presented alone or in pairs at 19 signal-to-noise ratios (-25 to 41 dB). When paired bands were tested, the level and signal-to-noise ratio (SNR) of one band were held constant while the level and SNR of the other band were varied. The listeners were 100 normal hearers, organized into five 20-person groups. Each group provided speech recognition data for one of five frequency regions (141-562, 562-1122, 1122-1778, 1778-2818, and 2818-8913 Hz). Comparisons of the results for each group indicated that IIFs vary with frequency and SNR. Current methods for predicting intelligibility from physical measurements of speech audibility would need to be revised in order to take such findings into consideration.

Adult↗