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W A Cooper

Publications and source records attributed to W A Cooper.

At least 19 recordsLinked to original sources
PubMed1992

Rate and frequency interactions in the auditory brainstem response of the adult rat.

Tone pip stimuli were used at different repetition rates to examine influences upon auditory brainstem response components. Rate increases to 80.1/s result in significant latency increases in waves IV and V at all test frequencies. Rate effects occur in rostral brainstem response components which show frequency related latencies different from wave I. Amplitude measures decline at higher repetition rates for waves I and IV at most test frequencies. Rate effects are most pronounced at 8 kHz stimulation which is around the optimal behavioral frequency in rat. At higher rates the second peak of wave I is enhanced at 8 kHz, whereas the third peak of wave I at 40 kHz disappears. These results demonstrate that tone-specific stimuli provide sensitive measures of latency, amplitude and wave morphology of components of the auditory brainstem response as a function of stimulus repetition.

Acoustic Stimulation↗
PubMed1992

Comparison of SSPL90 selection procedures.

Recommended SSPL90 values were determined at 500, 1000, and 2000 Hz for 16 subjects with mild-to-moderate sensorineural hearing losses using six different selection procedures, including an Upper Limit of Comfortable Listening (ULCL) and threshold-based procedure by Cox (1988), a threshold-based procedure by Seewald and Ross (1988), and loudness discomfort procedures by Berger (1988), McCandless and Lyregaard (1983), and Hawkins et al (1987) and Libby (1985). Statistically significant differences were found among the procedures at 500 and 2000 Hz. Analysis of individual data showed that while some subjects obtained similar recommended SSPL90s across the procedures, others showed dramatically different values.

Adult↗
PubMed1991

Effect of reference microphone location and loudspeaker azimuth on probe tube microphone measurements.

The effects of loudspeaker azimuth and reference microphone location on probe tube microphone measures were assessed. The real ear unaided response (REUR), real ear aided response (REAR), and real ear insertion response (REIR) were obtained on a KEMAR. Aided measures were obtained with both a behind-the-ear and an in-the-ear hearing aid. All three measurements were affected by changes in the loudspeaker azimuth and reference microphone location. Responses obtained with a 90 degree loudspeaker azimuth or with the reference microphone located at-the-ear revealed greater disparity than those obtained under other conditions. Most of the differences occurred at frequencies above 2000 Hz, with measurements utilizing the behind-the-ear hearing aid showing greater dispersion. These results suggest that the location of the loudspeaker and the reference microphone are important variables when utilizing probe tube microphone measurements.

Acoustics↗
PubMed1990

Auditory brainstem responses to tonal stimuli in young and aging rats.

The auditory brain stem response (ABR) was studied in young adult and aged rats using 3,8 and 40 kHz tone pips. The expected inverse relationship between frequency and latency was observed in the younger group for waves I, II and III, while the response to the highest frequency stimulus had the longest latency at wave V. Absolute latencies for waves I through V each showed age-related increments with more pronounced changes occurring to 3 and 40 kHz stimuli than to the frequency of maximum sensitivity (8 kHz). Threshold increases with age for the highest frequency approximately doubled those for the lower frequencies. Examination of interpeak intervals (IPI) I-III, III-V and I-V revealed aging effects. The largest IPI I-V increment occurred to 3 kHz stimulation which reflects changes at both I-III and III-V sub-intervals. These results demonstrate electrophysiological correlates of aging due to transformations in the peripheral auditory system coupled with alterations in brainstem auditory pathways.

Acoustic Stimulation↗
PubMed1990

Comparisons among SPLs in real ears, 2 cm3 and 6 cm3 couplers.

Sound pressure levels (SPLs) were measured in the ear canals of 30 adult subjects with standard audiometric earphones (TDH-39) and insert earphones (Etymotic ER-3A) and compared to those generated in 2 cm3 and 6 cm3 couplers. Transfer functions are shown for real ear to 2 cm3 coupler, real ear to 6 cm3 coupler, 6 cm3 to 2 cm3 coupler, and dB HL under standard earphones to 2 cm3 coupler SPL. In general, the data agreed rather well with published transfer functions that in most cases were derived by adding together a series of partial transfer functions from various studies. The conversion values from dB HL to 2 cm3 coupler SPL could be useful in selection of certain hearing aid parameters, but the intersubject variability may limit their usefulness somewhat.

Adult↗
PubMed1989

Use of probe tube microphone measurements in hearing aid selection for children: some initial clinical experiences.

Some initial experiences are described in which ear canal probe tube microphone measurements are used to determine hearing aid settings for children. Decisions are based upon ideas developed by Seewald and Ross (in Amplification for the Hearing Impaired, New York: Grune & Stratton, 1988: 213-267) and Seewald, Ross, and Stelmachowicz (J Acad Rehab Aud 1987;20:25-37) in which the long term spectrum of speech is amplified to desired sensation levels. Case results from four children are used to demonstrate the application and usefulness of the procedure.

Amplifiers, Electronic↗
PubMed1989

A comparison of three HA-1 couplers.

The use of 2-cm3 couplers for measuring the output of an ER-3A earphone has been recommended. The purpose of this study was to compare the acoustic output of three commonly available couplers and to study the intra- and inter-examiner reliability with which those measurements may be performed. While the repeatability of measurements, at least for clinical purposes, was good even for hand-held coupling of the earphone to the couplers, differences between couplers were observed. These differences were influenced by the positioning of the sound-outlet orifice relative to the interior, top wall of the couplers' cavities. A recommendation for 2-cm3 coupler calibration of the ER-3A earphone using a commonly available adapter was made.

Acoustics↗
PubMed1988

Reference threshold sound-pressure levels for the TDH-50 and ER-3A earphones.

Reference threshold sound-pressure levels were established for a new insert earphone, the ER-3A tubephone, and for the TDH-50 earphone. In test-retest comparisons, the tubephone produced estimates of auditory threshold as reliable as the thresholds produced by the supraaural earphone. Reference thresholds were developed for the two earphones from data contributed by three laboratories. While the TDH-50 data are in good agreement with the provisional ANSI 6-cc coupler reference levels (ASHA, 1982), the ER-3A data are at variance with the manufacturer's provisional recommendation for 2-cc coupler reference thresholds for frequencies below 1 kHz. The differences are attributed to physiologic noise that masked the lower frequency thresholds.

Acoustic Stimulation↗
PubMed1987

Development of auditory brainstem response to tone pip stimuli in the rat.

The course of development of the auditory brainstem response (ABR) in rat was examined. Pure tone pip stimuli of 3, 8 and 40 kHz at intensities up to 106 dB sound pressure level peak equivalent were presented to anesthetized rats on postnatal days (PND) 9, 10, 12, 14, 16, 20, 24, 36, 70 and 96. The peak-to-peak amplitude and the order of appearance of each wave was examined at each stimulus parameter. The first response to presentation of an auditory stimulus was observed on PND 12. This response was demonstrated to be of non-neural origin and presumed to be a summating potential representing hair cell function in the cochlea. The first neural responses, observed on PND 14, to 3- and 8-kHz tones only, appeared as two or more waves. High-frequency (40 kHz) tones did not elicit any substantive neural response on PND 14, but neural activity to this stimulus was observed consistently by PND 16. By PND 20, 4 waves were present consistently at all test frequencies, and by PND 36 the full adult complement of 5 vertex positive waves was recorded. The frequency-dependent sequential appearance of waves during development lends support to data charting the development of frequency mapping in the cochlea. The amplitude of waves I and II at 8 kHz decreased as the animal matured, while waves III-V generally showed an initial increase in amplitude at all test frequencies through PND 24 followed by a gradual amplitude decrease to adult levels. Possible sources for developmental changes in amplitude are discussed.

Animals↗
PubMed1985

Effects of normal and pathologic eardrum impedance on sound pressure in the aided ear canal: a computer simulation.

Reported herein are results of computer simulations of aided sound spectra in ears with normal and pathologic eardrum impedance. The computer technique used in this study has been reported elsewhere [D. P. Egolf, D. R. Tree, and L. L. Feth, J. Acoust. Soc. Am. 63, 264-271 (1978)]. Consequently, to develop reader confidence in the computer scheme, its application to real ears was first tested. This was accomplished by (1) comparing computed spectral data with in-the-ear measurements and (2) comparing real ear minus 2-cc coupler data-both computer generated--with an idealized difference curve published elsewhere [R. M. Sachs and M. D. Burkhard, unpublished rep. no. 20022-1, Industrial Research Products, Inc., Elk Grove Village, IL (1972)]. Results indicate that the wide variation in eardrum impedance among normals evidenced in other studies produces a corresponding wide variation in aided spectrum shape. Likewise, simulations utilizing two sets of pathologic eardrum impedance data obtained from the literature show that aided sound spectra in such ears are likely to be significantly different from those occurring in normal ears. These findings suggest, as others have concluded, that there may be a substantial variation in spectrum shape among individuals wearing identically the same hearing aid--even if those individuals have normal hearing. In conclusion, questions are raised about the use of real-ear simulators and the need for a comprehensive computer-based model of an entire hearing aid.

Acoustic Impedance Tests↗
PubMed1978

Combining auditory and visual stimuli in the adaptive testing of speech discrimination.

This investigation determined the feasibility of using both auditory and visual stimuli in the adaptive testing of speech discrimination. Thirty-six adults with normal hearing and vision were subjects. Using the adaptive methodology known as the Doublet technique, speech-discrimination testing using monosyllabic word lists from the Northwestern University Auditory Test No. 6 (NU-6) (Tillman and Carhart, 1966) was performed at the target levels of 29.3 and 70.7% for both auditory-only and auditory-visual conditions. The results indicated that a specific discrimination score could be obtained under more adverse listening conditions with the addition of visual cues. The contribution of visual cues was constant for the two target scores. The adaptive technique at the 29.3 and 70.7% targets was reliable for both the auditory-only and auditory-visual conditions. Constant level testing showed good agreement with the adaptive technique for the auditory-visual condition. In conclusion, the use of standard error calculations is useful in determining measurement errors and the effects of an aural rehabilitation program.

Acoustic Stimulation↗
PubMed1975

Effects of dichotically presented simulatneous synchronous and delayed auditory feedback on key tapping performance.

A selective replication of Tsunoda's (1966) application of the DAF key tapping paradigm to the study of functional auditory asymmetry was conducted. Present findings do not offer confirmation of Tsunoda's assertion that most subjects will exhibit performance disruption at a lower intensity level when a vowel is delayed at the right ear and when a pure tone is delayed at the left ear. In the present study, it was found that no difference existed between the pure tone and the vowel delayed to the left ear conditions in terms of performance deterioration. The significant difference in performance disruption between the vowel delayed to the right ear condition and the pure tone delayed to the right ear condition was interpreted to be suggestive of functional auditory asymmetry.

Auditory Perception↗
PubMedDate not supplied

Variable venting valve for earmolds.

The frequency response and loudness reduction characteristics of earmolds with variable venting valves (VVV) were investigated. Both side-branch and laterally vented earmolds were employed. Sound pressures were measured at 44 frequencies from 100 to 4 000 HZ in a modified HA-2 coupler with the VVV in four stages of opening: closed; 1/3 open; 2/3 open and 3/3 open. The effect of venting is primarily in the low frequencies. Little or no reduction in intensity is observed in the 'speech frequency' range and a modest amount is noted in the higher frequencies. The side-branch vented earmolds were more effective than the laterally vented earmolds. Calculated loudness reductions in phons were small. The effectiveness of the VVV, whether assessed by the frequency response or loudness reduction characteristics, is achieved within the first 1/3 of opening: further opening has little effect. The utility of the VVV, especially to the geriatric hearing aid user, is questionable.

Hearing Aids↗
PubMedDate not supplied

Problems with earphone calibration using a manikin.

The response of a single TDH-39 receiver mounted in a MX-41/AR and an Auraldome cushion was measured psychoacoustically and electroacoustically using standard couplers and the Zwislocki coupler mounted in KEMAR (Knowles Electronic Manikin for Acoustic Research). Although the psychoacoustic data were similar for both cushions, electroacoustic responses differed across cushions and across couplers. It was concluded that an accurate method for evaluating circumaural earphones has not yet been developed and the manikin, in its present form, is unsuitable for supra-aural or circumaural earphone calibration.

Acoustics↗
PubMedDate not supplied

Pure tone delayed auditory feedback: effect of instructions.

This study compared the effect of instructions to the subject upon key tapping performance with pure-tone delayed auditory feedback. One set of instructions stressed the importance of maintaining tapping rate whereas a second set emphasized consistency of the pattern. A third set stressed rate and pattern equality. The results lead to the recommendation that instructions stress equally both rate and pattern consistency.

Acoustic Stimulation↗
PubMedDate not supplied

Filter effect of earmold venting: comparison of electroacoustic and psychoacoustic methods of evaluation.

The filter effect of venting an earmold was evaluated by measuring the coupler-acoustic and threshold responses to open versus closed earmolds. In the coupler-acoustic technique the effect of venting was determined by measuring the output of the experimental earmolds seated on a modified 2-cc coupler with a specified signal impressed upon the earphone. The real ear threshold technique called for the determination of threshold by five listeners for the same earphone-earmold system. The data indicated that the difference between the coupler and threshold measures were of the same order of magnitude as the difference seen by other investigators reporting coupler and real ear-probe tube microphone measures. It was concluded that the threshold technique provides the same general description of the effects of venting an earmold as does the probe tube technique and should thus provide a useful method for determination of the filter effects produced by the venting of an earmold.

Auditory Threshold↗