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Biomedical subjects

G A Studebaker

Publications and source records attributed to G A Studebaker.

18 recordsLinked to original sources
PubMed1992

The effect of equating loudness on audibility-based hearing aid selection procedures.

Recently the articulation index (AI) has received a great deal of attention as a means to select hearing aid characteristics and to evaluate the merits of different hearing aid selection methods. These evaluations were based on the seldom modified assumption that the listening condition producing the largest AI is the best condition. The negative consequences of the differences in hearing aid conditions were seldom considered. In this paper it is shown that higher AIs are often achieved at the cost of substantially greater loudness. When gain adjustments are made to equate loudness across conditions, very different conclusions are reached about the relative merits of selection methods and the value of certain frequency-gain response modifications.

Algorithms↗
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↗
PubMed1989

Importance weighted audibility and the recognition of hearing aid-processed speech.

The purpose of this study was to determine the extent of the agreement between the speech-recognition performance of normally hearing subjects with each of six linear hearing aids and the performance predicted for those aids by a carefully derived articulation index. Also investigated was how much of the remaining variability in average subject performance across hearing aids could be attributed to harmonic distortion. It was found that predicted performance and average observed performance never differed by more than 8.4 rau (mean = 2.3 rau) and that the articulation index procedure used alone accounted for 90 to 94% of the variance in averaged subject performance.

Acoustics↗
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↗
PubMed1985

A "rationalized" arcsine transform.

Arcsine or angular transformations have been used for many years to transform proportions to make them more suitable for statistical analysis. A problem with such transformations is that the arcsines do not bear any obvious relationship to the original proportions. For this reason, results expressed in arcsine units are difficult to interpret. In this paper a simple linear transformation of the arcsine transform is suggested. This transformation produces values that are numerically close to the original percentage values over most of the percentage range while retaining all of the desirable statistical properties of the arcsine transform.

Mathematics↗
PubMed1978

Absolute and relative reliability of several response parameters used in vestibular assessment.

This experiment investigated the reliability of five indices used to express the magnitude of induced vestibular nystagmus. The investigation was undertaken because information concerning the reliability of the various response parameters when caloric testing is repeated on the same subject is limited. Electronystagmographic assessments of the nystagmus response to the Fitzgerald-Hallpike test were obtained from 16 subjects on three occasions with equal intervals of time between occasions. The data were statistically treated with an analysis of variance technique that allows the generation of correlation coefficients. The findings showed that speed of the slow phase, total beats, culmination frequency, and total amplitude reliably express the magnitude of induced nystagmus on repeated tests. Duration of the induced reaction was not as reliable as the other indices on repeated testing. In addition, difference scores were more repeatable than absolute scores and the caution that must be maintained when using correlation coefficient analyses to estimate reliability is highlighted.

Adolescent↗
PubMedDate not supplied

Directivity of the human vocal source in the horizontal plane.

The directional characteristics of a male and a female voice in the horizontal plane were measured in an anechoic room. Results were compared with the only two other studies known to have been done using human subjects. The results of the three studies agree very well. The directional characteristics of two loudspeakers were also measured. One loudspeaker, about the size of the human head, did a fairly good job of emulating the directional characteristics of the human vocal source. Another large loudspeaker did a very poor job. The directional characteristics of a manikin designed and evaluated by Olson (1972. J. Audio. Eng. Soc. 20, 446-451) agreed well with the averaged results from the three studies of human talkers.

Acoustics↗
PubMedDate not supplied

Earmold modification effect measured by coupler, threshold and probe techniques.

The validity of probe tube microphone measurements in providing data indicative of the magnitude of the change in subjects' threshold resulting from changes in earmold configuration was investigated. The relationship between these measures in the real ear canal and the changes observed in 2-cm3 and Zwislocki couplers under similar circumstances or earmold modification was also measured. Standard, vented and 'open' earmold conditions were utilized. Threshold and probe-tube measurements were made. Statistical evaluation revealed that these two techniques did not produce significantly different results except at 125--165 Hz, where noise masking may have been a factor influencing the threshold data. Neither coupler as used gave an accurate quantitative estimate of the in-use effects of vented earmolds or the open earmold configuration, but the Zwislocki coupler gave a better approximation than the 2-cm3 coupler.

Acoustic Stimulation↗
PubMedDate not supplied

Hearing-aid-processed signals: a new approach.

A new protocol for obtaining and utilizing hearing-aid-processed signals in hearing aid research or hearing aid selection is described. Data are presented which illustrate the extent to which this procedure may be expected to result in a signal spectrum at the subject's eardrum which is the same as the spectrum the subject would have received if the hearing aid itself had been placed on his ear (a directly-aided situation). An earlier investigation by the authors indicated that the traditional protocol for the production and utilization of hearing-aid-processed signals results in substantial discrepancies between these two spectra. The data presented were obtained using the KEMAR as the subject with a Zwislocki coupler as the KEMAR's ear canal/eardrum. The discrepancy between directly-aided and hearing-aid-processed spectra was typically +/- 2 dB for ear-level hearing aids fitted using standard, vented, or open earmolds (in open earmold fittings only the amplified component of the directly-aided spectrum is reproduced).

Acoustic Stimulation↗
PubMedDate not supplied

Spectral changes produced by earphone-cushion reproduction of hearing aid-processed signals.

This investigation was conducted to assess the extent to which hearing aid-processed signals present an acoustic signal to the subject which has a frequency response equivalent to that which the hearing aid itself would have provided. The frequency response of a hearing aid receiver which was coupled directly to the ear canal ("aided" condition) was compared with the frequency response of the same receiver when its output was recorded on magnetic tape and then presented to the subject via a TDH-49 earphone ("pseudoaided" condition). Results indicated that when the earphone was mounted in an MX-41/AR cushion or either of two circumaural cushions, the spectrum of the sound arriving at the subject's eardrum in the pseudoaided condition was substantially different from the spectrum delivered in the aided condition.

Hearing Aids↗
PubMedDate not supplied

Side branch and parallel vent effects in real ears and in acoustical and electrical models.

The purpose of the project was to demonstrate and explain the acoustic effects of side branch and parallel vents in individual real ears. It was shown that parallel and side branch vents produce similar low frequency filtering effects and vent-associated reactance resonances. However, when the input system incorporates a side branch vent the sound pressure produced in the ear canal at frequencies above the vent-associated resonance is less than that produced when the input system is unvented. This effect is not seen when the input system is associated with a parallel vent. Data obtained in the real ear canals were compared to analogous measurements made using an acoustical model (the Zwislocki coupler) and an electrical model designed to simulate the hearing aid receiver, input tubing, earmold, ear canal, and eardrum. Both models yielded data very similar to the real ear results. The advantages of each model in predicting the effects of individual earmold vents are discussed.

Ear Canal↗
PubMedDate not supplied

Sound levels in a 2-cc cavity, a Zwislocki coupler, and occluded ear canals.

Probe-tube measurements of the differences in sound levels at three locations in ear canals were compared to the differences in levels measured at analogous positions in a Zwislocki coupler and a 2-cc cavity. The results support the recommendation of Sachs and Burkhard that probe tube measurements should not be made with the probe tube flush with the earmold tip and close to the sound inlet bore. In real ear canals the transfer functions to the eardrum presented by Bruel, Frederikson, and Rasmussen and by Studebaker agree well with each other but differ somewhat from the one used by Sachs and Burkhard. In agreement with Bruel et al., the data of this study reveal a plateau in the relationship between real ear and 2-cc cavity responses between about 1.6 and 4.0 kHz, the relative intensity level of which may depend upon residual ear canal volume.

Acoustics↗