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Biomedical subjects

W A Cooper

Publications and source records attributed to W A Cooper.

At least 37 records · Page 2Linked to original sources
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

Stimulus artefact reduction systems for the TDH-49 headphone in the recording of auditory evoked potentials.

Standard audiometric transducers, such as the TDH-49, produce an electrical artefact which interferes with the recording of the early auditory evoked potentials. The sources of these artefacts have been identified as the capacitive and inductive coupling of the transducer and its leads to the recording electrodes. Artefacts were recorded using an artificial head with an M2-Cz electrode array for 500- and 3-kHz tone pips and positive, negative, and alternating polarity clicks at Peak Equivalent Sound Pressure Levels from 60 dB (positive click and 3-kHz tone pip) to 90 dB (alternating polarity click). The artefacts grew linearly with increases in intensity. Shifts in the Visual Detection Threshold of the artefacts produced by various conditions of shielding the transducer and its leads were explored. Acceptable reductions in artefact magnitude were obtained by enclosing the transducer in either an aluminium or mu-metal case connected through a braided-wire shield of the transducer leads to earth ground. Lesser reductions were achieved by the use of antiphase cancellation. The combination of the latter and the aluminum and mu-metal cases did not produce greater shifts in the visual detection threshold than the use of the aluminum and mu-metal cases alone. The fabrication of a pair of shielded enclosures is described and data are presented which show that they do not adversely affect the acoustic output of the headphones.

Acoustics↗
PubMedDate not supplied

Delayed feedback audiometry: reliability of repeated measures.

The test-retest reliability of hearing thresholds at 1000 Hz measured by a delayed auditory feedback procedure was compared with the reliability of thresholds obtained with voluntary responses to the same signal in 10 adults with normal hearing sensitivity. Thresholds for each procedure were obtained three times on each of 5 different days. Although the delayed feedback procedure yielded estimates of threshold which averaged 4.6 dB greater than those estimated by voluntary responses (p less than 0.05), there was no evidence that experience over time resulted in a change for the poorer in the precision of the test.

Adult↗
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

Estrogen treatment and age effects on auditory brainstem responses in the post-breeding Long-Evans rat.

The auditory brainstem response (ABR) was recorded from 20-month-old Long Evans hooded female rats to determine if latency reductions occur from estrogen replacement. The ABR in these post-breeding age rats was also examined for reductions in response latencies as a function of adult age. Tone pip stimuli (8 and 40 kHz) were presented at 21, 51, or 81 s(-1). Aging control and ovariectomized animals showed slower response latencies for waves Ib-VI than young adults for 8 and 40 kHz stimulation at 21 s(-1). Increased stimulus rate resulted in longer latencies for all waves at 20 months. In contrast to hormone treatment effects in young adults, ABR latencies in post-breeding age estrogen-treated animals were not reduced, consistent with a general decrease in CNS responsiveness to estrogen steroids associated with age. The results also suggest that sensorineural modifications in the auditory system which prolong ABR latencies can occur early in the aging process of adult female subjects.

Aging↗
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

"Rhabdoid meningioma" lacking malignant features. Report of two cases.

We report 2 cases of meningiomas with rhabdoid morphology but lacking histological features of malignancy. Both occurred in adult women, one arising from the superior surface of the tentorium and the other in the Sylvian fissure. The tumors showed light microscopic, immunohistochemical and ultrastructural evidence of meningothelial differentiation together with diffuse or focal areas exhibiting rhabdoid morphology. The rhabdoid areas were characterized by cells with large cytoplasmic eosinophilic inclusions and large eccentric nuclei. Both cases showed areas with sheet-like growth and one had macronucleoli and brain invasion. The same case showed areas of necrosis that most likely related to pre-operative arterial embolization. Unlike most cases reported in the literature, these "rhabdoid meningiomas" lacked significant mitotic activity or other atypical features. The diagnostic and prognostic significance of this tumor entity is discussed along with a review of the literature.

Adult↗