PubMed Health⌕ Search

Biomedical subjects

R L Sherbecoe

Publications and source records attributed to R L Sherbecoe.

12 recordsLinked to original sources
PubMed1995

Evaluating relative speech recognition performance using the proficiency factor and rationalized arcsine differences.

This study evaluated two measures that have been used to compare the performance of particular subjects to outcomes predicted by the articulation index (Al). One measure was the proficiency factor, that is, the ratio between the Al derived from a test score and the Al derived from objective measurements of speech and noise spectra. The other measure was the difference between rationalized arcsine transforms of the observed score and the score predicted from the Al. The results indicated that rationalized arcsine differences are statistically superior to proficiency factors for comparing two sets of scores. Proficiency factors are best used to correct the Al, and thus an expected score, for the effects of subject variables that might bias the comparison. An assessment procedure that combines the strengths of both measures is described.

Computer Simulation↗
PubMed1994

The effect of noise spectrum on speech recognition performance-intensity functions.

Articulation theory predicts that a subject's absolute or masked threshold configuration will affect the slope of the speech recognition performance-intensity (P-I) function. This study was carried out to test that prediction. Performance-intensity functions for the Technisonic Studios W-22 recordings were obtained from 12 subjects with normal hearing. Four continuous thermal noise maskers, high-pass (HP) noise, white noise, ANSI noise, and talker-spectrum-matched (TSM) noise, were used to shape threshold. P-I function slopes for the averaged data ranged from about 1.6%/dB in HP noise to about 6.7%/dB in TSM noise. At low to moderate speech intensity levels, the positions and slopes of the P-I functions were accurately estimated by an articulation index-type model that included corrections for subject proficiency and for high- and low-frequency spread of masking. At higher intensity levels, performance was overestimated by the model.

Acoustic Stimulation↗
PubMed1993

Frequency-importance and transfer functions for the Auditec of St. Louis recordings of the NU-6 word test.

Frequency-importance and transfer functions for the Auditec of St. Louis recordings of the NU-6 word test are reported. The functions were derived from the word recognition scores of 24 subjects with normal hearing who were tested under 128 conditions of filtering and talker-spectrum-matched noise. The importance function was broader and had a lower midpoint than the NU-6 importance function reported by Schum, Matthews, and Lee (1991), but still displayed a bimodal shape. The transfer function was steeper than the transfer function reported by Schum et al., but comparable in slope to the transfer function for low-context CNC words reported by Bell, Dirks, and Trine (1992). Results from a limited set of conditions presented in quiet suggest that the use of masking noise was partly responsible for the dissimilar importance and transfer functions obtained by Schum et al. and this study. Differences in the equipment used in each experiment and in the methods used to analyze the data appear to have contributed as well.

Acoustic Stimulation↗
PubMed1993

Speech spectra for six recorded monosyllabic word tests.

Speech spectra (long-term RMS levels and 1% speech peaks) in third-octave bands were determined for six monosyllabic word test materials: digital recordings of the Central Institute for the Deaf W-22 word test and the Northwestern University NU-6 word test obtained from Qualitone; audiotape recordings of the Central Institute for the Deaf W-22 word test, the Northwestern University NU-6 word test, and the Harvard Psycho-Acoustic Laboratory PB-50 word test obtained from Auditec of St. Louis; and an audio-tape recording of the Maryland CNC word test obtained from Olsen Distributors. The spectra were generally within 2 SD of previous results for continuous speech spoken by an average male talker (Cox, Matesich, & Moore, 1988; Cox & Moore, 1988), but differed sufficiently from those data and from one another to affect the accuracy of Articulation Index calculations. The relationship between the level of the calibration tone and the speech in the third-octave band centered at 1000 Hz was different for each recording.

Acoustic Stimulation↗
PubMed1993

Performance-intensity functions at absolute and masked thresholds.

In most applications of audibility and articulation theories, it is assumed that absolute thresholds and thermal noise maskers affect speech recognition performance-intensity (P-I) functions similarly. The purpose of this study was to evaluate that assumption. Performance-intensity functions for NU-6 monosyllabic words were obtained from eight normal-hearing subjects in quiet and in the presence of two levels of a noise that produced masked pure-tone thresholds parallel to, but higher than, those of each individual in quiet. The results support the practice of treating absolute threshold as a noise-masked threshold in predictions of speech recognition performance.

Acoustic Stimulation↗
PubMed1991

Frequency-importance and transfer functions for recorded CID W-22 word lists.

Frequency-importance and transfer functions for the Technisonic Studios' recordings of the CID W-22 word test are reported. These functions may be used to calculate Articulation Index (AI) values or to predict scores on the W-22 test. The functions were derived from the word recognition scores of 8 normal-hearing listeners who were tested under 308 conditions of filtering and masking. The importance function for the W-22 test has a broader frequency range and a different shape than the importance function used in the current ANSI standard on the Articulation Index (ANSI, 1969). The transfer function is similar in slope to the ANSI transfer function for 256 PB-words, but is shifted to the right of that function by 0.05 AI.

Adult↗
PubMed1988

Magnitude estimations of the intelligibility and quality of speech in noise.

Inexperienced normal hearing listeners judged the intelligibility and quality of hearing aid processed speech using magnitude estimation. Four trials were conducted for each judgment type at two S/N ratios, 0 and 7 dB. There were no significant effects due to judgment type, S/N ratio or trial; however, noticeable differences in the variability of these factors were apparent. Inter- and intrasubject standard deviations for quality estimations were lower than for intelligibility estimations while intersubject standard deviations were greater at 0 dB than at 7 dB S/N ratio and decreased over trial. Overall intrasubject variability was greater than would probably be acceptable for clinical applications. Across hearing aid conditions, magnitude estimations were positively correlated with word recognition scores but were less affected by changes in S/N ratio.

Adolescent↗
PubMed1988

Frequency importance functions for a feature recognition test material.

The relative importance of different parts of the auditory spectrum to recognition of the Diagnostic Rhyme Test (DRT) and its six speech feature subtests was determined. Three normal hearing subjects were tested twice in each of 70 experimental conditions. The analytical procedures of French and Steinberg [J. Acoust. Soc. Am. 19, 90-119 (1947)] were applied to the data to derive frequency importance functions for each of the DRT subtests and the test as a whole over the frequency range 178-8912 Hz. For the DRT as a whole, the low frequencies were found to be more important than is the case for nonsense syllables. Importance functions for the feature subtests also differed from those for nonsense syllables and from each other as well. These results suggest that test materials loaded with different proportions of particular phonemes have different frequency importance functions. Comparison of the results with those from other studies suggests that importance functions depend to a degree on the available response options as well.

Acoustic Stimulation↗
PubMed1987

A frequency importance function for continuous discourse.

Normal hearing subjects estimated the intelligibility of continuous discourse (CD) passages spoken by three talkers (two male and one female) under 135 conditions of filtering and signal-to-noise ratio. The relationship between the intelligibility of CD and the articulation index (the transfer function) was different from any found in ANSI S3.5-1969. Also, the lower frequencies were found to be relatively more important for the intelligibility of CD than for identification of nonsense syllables and other types of speech for which data are available except for synthetic sentences [Speaks, J. Speech Hear. Res. 10, 289-298 (1967)]. The frequency which divides the auditory spectrum into two equally important halves (the crossover frequency) was found to be about 0.5 oct lower for the CD used in this study than the crossover frequency for male talkers of nonsense syllables found in ANSI S3.5-1969 and about 0.7 oct lower than the one for combined male and female talkers of nonsense syllables reported by French and Steinberg [J. Acoust. Soc. Am. 19, 90-119 (1947)].

Adolescent↗
PubMed1987

Spectrum shaping with a hardware digital filter.

Digital filters have certain characteristics which make possible some things that are either difficult or essentially impossible using analog equipment. Among the most useful characteristics are steep transition band slopes and the capability to shape the passband transfer function in great detail. Unlike most digital filters implemented in software, hardware digital filters can be used to filter signals in real-time. Also, they can be designed to provide a linear phase response. They have some disadvantages as well, however, including moderately high cost, the need for supporting equipment, and at the present time, the need for a moderate degree of computer programming and interfacing skill. We have used hardware digital filters in a number of applications. These applications and the relevant filter performance characteristics are described.

Acoustics↗
PubMed1986

An articulation index based procedure for predicting the speech recognition performance of hearing-impaired individuals.

An articulation index calculation procedure developed for use with individual normal-hearing listeners [C. Pavlovic and G. Studebaker, J. Acoust. Soc. Am. 75, 1606-1612 (1984)] was modified to account for the deterioration in suprathreshold speech processing produced by sensorineural hearing impairment. Data from four normal-hearing and four hearing-impaired subjects were used to relate the loss in hearing sensitivity to the deterioration in speech processing in quiet and in noise. The new procedure only requires hearing threshold measurements and consists of the following two modifications of the original AI procedure of Pavlovic and Studebaker (1984): The speech and noise spectrum densities are integrated over bandwidths which are, when expressed in decibels, larger than the critical bandwidths by 10% of the hearing loss. This is in contrast to the unmodified procedure where integration is performed over critical bandwidths. The contribution of each frequency to the AI is the product of its contribution in the unmodified AI procedure and a "speech desensitization factor." The desensitization factor is specified as a function of the hearing loss. The predictive accuracies of both the unmodified and the modified calculation procedures were assessed by comparing the expected and observed speech recognition scores of four hearing-impaired subjects under various conditions of speech filtering and noise masking. The modified procedure appears accurate for general applications. In contrast, the unmodified procedure appears accurate only for applications where results obtained under various conditions on a single listener are compared to each other.

Adult↗