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Apr 1980

Volume 67, Issue S1, pp. S1-S103

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back to top Session MM. Physiological Acoustics III: General (Poster Session)
Contributed Papers
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Acoustic properties of the external auditory canal in chinchilla, guinea pig, cat, and man (A)

D. C. Teas, R. E. Hill, D. F. Dolan, J. P. Walton, J. H. Patterson, and C. K. Burdick

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S88-S88 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The acoustic pressures produced by a band of noise were measured at the entrance to the auditory canal and near the tympanum. The stimuli was produced by a TDH‐39 earphone activated by a noise band tailored to produce an approximately flat spectrum between 0.1 and about 4 kHz at the entrance to the ear canal. A computer program calculated the output power spectra, the signal/noise, the cross‐power spectrum, the transfer function, the coherence function, and the phase between the input and output power spectra. The transfer function in each animal shows an upper frequency peak, the location of which varies with the apparent volume of the canal, being highest for the guinea pig and lowest for man. The magnitude of the resonance is largest for the cat and smallest for the guinea pig. [Supported in part by DAMD 17‐78C‐8067 and NSF‐77‐16907.]
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Spectrum of the CM produced by high‐intensity, low‐frequency noise bands in the chinchilla (A)

D. C. Teas, R. E. Hill, D. F. Dolan, J. P. Walton, J. H. Patterson, and C. K. Burdick

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S88-S88 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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High‐intensity, low‐frequency octave band noise in the free field has been reported to produce permanent threshold shift at 2 kHz in chinchillas [Burdick, Patterson, Mozo, and Camp, J. Acoust. Soc. Am. 64, 458 (1978)]. We have delivered 100‐ and 250‐Hz low‐pass noise to the chinchilla with intact pinna but open bulla and have measured the spectrum of the CM recorded with electrodes in turn I and turn II. SPL's were measured at the pinna. The output of the microphone was led to channel 1 of an A/D converter. The CM was led to channel 2. The inputs to the A/D's were adjusted to the same rms level to minimize digital noise. A computer program calculated FFT's and produced several calculations from them (see previous abstract). At SPL's below 100 dB, the output spectrum (CM) is similar to the input spectrum (microphone). Above 100 dB the output spectrum contains frequencies above the passband of the input spectrum. The coherence function indicates that the high‐frequency output is not present in the input power spectrum. [Supported in part by DAMD17‐78C‐8067 and NSF 77‐16907.]
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Natural frequencies of a finite‐element model of the cat eardrum (A)

W. Robert and J. Funnell

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S88-S88 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The vibrations of the cat eardrum are being modelled using the finite‐element method. The three‐dimensional, linear, low‐frequency model previously reported [W. R. J. Funnell, J. Acoust. Soc. Am. 63, 1461–1467 (1978)] has been further developed by the addition of inertial terms. The first several natural frequencies have been calculated as functions of various parameters of the model, including drum curvature and ossicular load. The ossicular moment of inertia strongly affects the lowest natural frequency, but has little effect on the higher ones. The three‐dimensional curvature of the eardrum affects the higher modes most strongly. The importance of quantitative eardrum shape measurements [W. R. J. Funnell, J. Acoust. Soc. Am. 65, S9 (1979)] is discussed. [Work supported by the Medical Research Council of Canada.]
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Neural response patterns for frequency.changing signals (A)

S. E. Shore and J. K. Cullen, Jr.

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S88-S88 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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In previous studies, whole nerve AP's recorded from the guinea pig VIII nerve were shown to differ in response to 5‐ms rising and falling frequency tone glides (Shore and Cullen, 1978). The rising glide resulted in larger N1 and N2 amplitudes. The present study examined AP's in response to 2‐ms rising and falling glides with seven differing rates of frequency change. Waveform analysis indicates greater N1 and N2 amplitudes in response to the rising glides for rates of change up to 160 Hz/ms. At rates of change greater than 160 Hz/ms, amplitudes are larger for the falling glide. Later peaks show larger amplitudes for rising glides at all rates, suggesting convergence of neural input. These findings suggest that directional responses to frequency‐changing signals reported for higher‐order neurons are not solely a function of neuron type. Rather, differential coding is initiated at a cochlear level. [Work supported in part by NIH.]
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Coding of interaural time differences in the microsecond range by auditory units of echolocating bats (A)

G. Harnischfeger

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S88-S88 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The coding of interaural time differences (Δt) by single auditory units was investigated by extracellular recordings from the brainstem in the echolocating bat, Molossus ater. Phase‐locked constant frequency tone bursts (2 ms duration, 0.5 ms rise/decay‐time) delivered through earphones could be time delayed with an accuracy of <1 μs by using two “bucket‐brigade‐devices.” Nine percent of the 79 binaural units studied showed dependence on Δt‐variations in the animals' relevant time range (±50 μs 17 mm interaural distance). From the steepest Δt‐impulse count functions measured for a fixed interaural intensity difference, a minimum detectable time difference of less than 4 μs could be calculated. These small time differences were coded from the envelope of signals with comparatively long rise times. The use of phase differences can be excluded. Due to the high best frequencies of the units (18–61 kHz) the half periods of the sine waves were always shorter than the working ranges of the Δt‐impulse count functions measured. Furthermore, the Δt‐functions were never periodic. [Work supported by DFG: Br 593/2, Ne 146/10, and SFB 45.]
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Neuronal critical bands (NCBs)—Determined for single units of the inferior colliculus of the CF‐FM bat Rhinolophus ferrumequinum (A)

R. Engelstätter

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S89-S89 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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NCBs, were estimated by determining the thresholds for noise of variable bandwidth centered around the best frequency (BF) of the neuron and by masking a pure tone at the BF with the same noise. In most cases the values can be fitted by two straight lines whose intersection defines the size of the NCB. Single units with a BF in the frequency range of the CF‐orientation call (about 83 kHz) are characterized by extremely small NCBs (0.2–0.4 kHz). For neurons with a BF around 81.5 kHz the sensitivity for noise is lower as expected from the psychophysical critical ratio (CR) curve of Rhinolophus [Long, G. R., J. Comp. Physiol. 116, 247–255 (1977)]. Presumably the high signal‐to‐noise ratios (SNRs) in this frequency range are responsible for this discrepancy. No correlation was found between the size of the neuronal CRs estimated from the SNR measured with wide‐band noise and the size of the NCB. [Work supported by DFG Br 593/2.]
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COCB stimulation alters cochlear mechanics as reflected in earcanal pressure measurements (A)

D. C. Mountain

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S89-S89 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The distortion product (f2 − f1) was measured in the sound pressure near the eardrum. Stimulation of the cochlear efferents (COCB) decreased the level of the distortion product. The percent reduction was largest at lower primary intensities. A decrease of the endocochlear potential (EP) caused a similar decrease in the distortion product. A decrease in EP would presumably depolarize the apical hair cell membrane and would hyperpolarize the basal and lateral portions of the membrane. The efferent stimulation would hyperpolarize the entire membrane. A comparison of the two types of experimental results suggests that the potential across the lateral or basal portion of the hair cell membrane plays an important role in influencing the linearity of cochlear mechanics.
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Cochlear potentials in deafness and jerker mice (A)

Gregory R. Bock and Karen Steel

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S89-S89 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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Anatomical studies using light microscopy have shown that mice affected by the deafness or jerker genes develop cochlear hair cells which at first appear to be normal. The hair cells then begin to degenerate, and by about three months of age most of the organ of Corti has degenerated. The object of the present study was to determine whether the cochleas of affected animals are functionally normal during the period when they appear structurally normal. Mice from the two strains aged between 12 and 50 days were anaesthetized and audiograms were determined by measuring thresholds for detecting the compound action potential recorded at the round window. No action potentials or cochlear microphonics could be recorded from affected animals at any age but littermates unaffected by the respective genes had normal thresholds. These results indicate that the apparent structural integrity of the cochleas of young deafness and jerker mice is not accompanied by normal function. Mice affected by these genes appear to be completely deaf at all stages of cochlear development.
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Signal detection by low‐frequency cells of the ventral cochlear nucleus (A)

Ted L. Langford and Jaswant S. Gidda

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S89-S89 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The responses of low‐frequency, “primary‐like” cells of the ventral cochlear nucleus to several signal‐masker combinations were measured. Signals were 100‐ms, best‐frequency tones. Maskers were either wide‐band (0–10 kHz) or narrow‐band (0.2 × cell's best frequency) “multiplied” noises presented either continuously or gated with the signal. Masker levels were held constant while signal levels were varied in 2‐dB steps over a signal‐to‐noise ratio (S/N) range of +5 to +23. Little correlation was found between SIN and discharge rate for any condition. A nearly linear relationship between S/N and the degree of phase locking, as measured by the synchronization coefficient, existed, however, for all conditions. For the population of units sampled, it appears that information regarding the presence of a partially masked, low‐frequency signal is carried in the form of phase‐locked responses. [Work supported by NIH.]
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Can intensity discrimination be uniquely related to available data (A)

H. S. Colburn

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S89-S89 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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Predictions of intensity discrimination models depend critically on assumptions about the following aspects of auditory‐nerve activity: The nature of the randomness; the importance of the time structure relative to the mean rate of firing (count); the saturation of the rate‐intensity function; the distribution of thresholds of fibers with a common characteristic frequency (CF): the distribution of CF's over fibers; the shapes of tuning curves, especially the tails; the dependence of the rate‐intensity functions both on the CF relative to the stimulus frequency and on other characteristics of the fiber (e.g., spontaneous rate); and the nonlinear interactions that occur with several stimulus components (as in partial masking experiments). In addition, predictions are sensitive to the way information from different fibers is assumed to be combined centrally. Unfortunately, there exist different sets of assumptions that both correctly predict the psychophysical data and are roughly consistent with available physiological data. In spite of this theoretical latitude, many current models make assumptions that contradict available physiological data. [Work supported by NIH.]
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Effects of glutamate and aspartate on tone‐evoked and spontaneous activity in posterior ventral and dorsal cochlear nucleus (A)

D. M. Caspary

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S89-S89 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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As previously reported [Caspary and Havey, Neurosci. Absts. 5, 17 (1979)], iontophoretic application of the excitant amine acids, glutamate and aspartate, can affect thresholds and response patterns of cochlear nucleus (CN) neurons. This and recent data [Godfrey et al., J. Histochem. Cytochem. 25, 417 (1977); Wenthold, Brain Res. 143, 544 (1978); 162, 338 (1979)] support the hypothesis that glutamate and/or aspartate may be the neurotransmitter(s) at acoustic nerve endings. Control rate‐intensity curves were obtained from neurons in the posterior ventral CN “on” and “chopper” responders) and dorsal CN (“pauser” and “build‐up” responders). Rate‐intensity curves shifted to the left with iontophoretic application of effective dose levels of glutamate and aspartate. Data plotted as percent increase (above control response) against intensity demonstrated that the largest changes occurred at near threshold intensities. “Chopper” neurons displayed increased non‐tone‐evoked activity at lower doses (2–150 hA) of excitant amino acids than “on,” “pauser,” and “build‐up” neurons (100–250 nA). These data further demonstrate that glutamaro and aspartate can differentially affect CN neurons. [Supported by NIH and the Deafness Research Foundation.]
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Neural generators of brainstem auditory‐evoked responses (A)

Richard H. Britt and Glenn T. Rossi

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S89-S90 (1980); (2 pages)

Online Publication Date: 11 Aug 2005

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In a series of 55 pentobarbital anesthetized cats, discrete lesions (36 animals) and gross electrode recordings (28 animals) were made in the nuclei and tracts of the ascending auditory pathway. Ten per second clicks were presented monaurally, and the responses averaged from differential recordings between vertex and mastoid. Cochlear microphonic (CM) was monitored from round window electrodes. Five waves (I‐V) were routinely recorded. Wave I matched the latency of N1 of the CM and remained, although significantly elongated in configuration, after complete aspiration of the cochlear nucleus (CN). If the CN were surgically isolated, or large lesions made of the ipsilateral superior olivary complex (SOC), all but waves I and II disappeared. Wave III was most affected by large lesions of either SOC. Activity with a latency of wave III was recorded from either SOC and, to a lesser extent, from the trapezoid body, the latter of which also had activity with a latency of wave II. Activity with a latency of wave IV was recorded in the region of the lateral lemniscus extending caudally to the SOC and rostrally to the inferior colliculus, but primarily in the dorsal nucleus of the LL. Activity compatible with wave V was seen only in either inferior colliculus. This work suggests that there are ipsilateral neural generators of waves I and II and multiple bilateral neural generators for waves III, IV, and V. [Work supported by VA RAG and Merit Review Grants and the Stanford Neurosurgery Research Fund.]
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Effects of MRF stimulation on the auditory‐evoked potential (A)

J. Michael Cassady, Richard Lewis, and Leonard M. Kitzes

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S90-S90 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The effects of mesencephalic reticular formation (MRF) stimulation on cortical‐evoked potentials was studied in nine cats. The interval between MRF stimulation and delivery of tonal stimuli (i.e., delay) was varied as was the intensity of electrical stimuli at 52 sites in MRF. The effects of MRF stimulation on auditory‐evoked potentials were, as in the visual system, time dependent: with a 30 ms delay, the N1 wave (latency 10–15 ms) was usually augmented; with a 25 ms delay, the P2 wave (latency 20–25 ms) was consistently suppressed; with a 5 ms delay, the N2 wave (latency 35–50 ms) was consistently augmented. The most effective stimulation sites were sharply localized within MRF. Stimulation alone at these sites elicited large field potentials in auditory cortex with a peak latency of 30–50 ms and a duration of 80 ms. Stimulation of neighboring sites evoked only marginal changes even with increased current. Pupillary behavior, used as an experimental control, was affected by broader areas within the MRF. [Work supported by NIH.]
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Phase sensitivity of human frequency‐following response to the “missing fundamental.” (A)

Steven Greenberg and James T. Marsh

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S90-S90 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The pitch of a harmonic signal is not appreciably changed upon alteration of the component phase configuration for tones of low harmonic rank (<harmonic 8) (Bilsen, 1973). This implies that the “central pitch processor” is insensitive to the relative phase of the signal's frequency components. Farfield, vertex‐derived, frequency‐following responses (FFR) (representing the integrated activity of phase‐sensitive neurons of the upper brainstem pathway) were recorded during presentation of three‐component (F1 = 732 Hz, F2 = 976 Hz, F3 = 1220 Hz) tone bursts of variable phase configuration. For each series, stimuli were identical in all respects except for the starting phase of F2. F1 and F3 always began in sine phase. The starting phase of F2 varied from 0° to 180° in 45° steps. FFR amplitude at the fundamental frequency (244 Hz) (as determined by spectral analysis) varies as a function of phase configuration when all three frequency components are of equal intensity. However, when the level of F2 is 6 dB above F1 and F3, FFR amplitude is unaffected by changes in stimulus phase configuration. These results suggest that FFR to the “missing fundamental” is determined principally by the frequency and relative amplitude of the stimulus harmonics rather than by characteristics of the aggregate stimulus waveform (such as envelope modulation pattern).
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Backward masking of human brainstem responses (A)

R. R. Stanny, V. E. Peeples, and L. F. Elfner

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S90-S90 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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Backward masking of wave V responses was investigated as a function of probe‐to‐masker intensity ratio (Ip/Im) and interstimulus silent interval (Δt). Stimuli were 0.5‐ms segments of broadband noise with N0 from 20 to 55 dB SPL. Maskers were always 55 dB SPL (about 45 dB SL). Values of Δt ranged from 0.5 to 8.0 ms. Combinations of (Ip/Im) and Δt which produced probe and masker responses of identical latency profoundly reduced probe responses. Here, the response to probe‐plus‐masker was negligibly larger than that to masker alone and reliably (i.e., with p > 0.995) smaller than that to a stimulus 3 dB above Im. When probe and masker responses partially overlapped, the probe response peaked first, and Ip/Im was less than about ‐20 dB, the probe response was masked in the region of overlap. When Ip/Im exceeded about ‐20 dB, partial or near overlap produced strong forward masking of the nominal masker's response. Backward masking was not observed when probe and masker responses did not overlap, nor when probe and masker were presented to opposite ears.
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Computer‐averaged input‐output curves and visual detection levels in methylmercury‐poisoned guinea pigs (A)

C. Wilpizeski

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S90-S90 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The present electrophysiological study was done to confirm an expected low‐tone dysfunction in guinea pigs poisoned with cumulated doses of methylmercury. Forty young‐adult Hartley strain guinea pigs were fitted stereotaxically with permanent recording electrodes having tips in the auditory tubercle and on the dural surface of the cerebrum. Twenty animals were injected subcutaneously with cumulated doses (2 mg/kg/day) of methylmercury chloride solution five times per week for periods ranging from 10 to 38 days. Twenty control subjects were injected with comparable volumes of sterile water. Click‐ and pure‐tone‐evoked responses were recorded during the waking state using a summing computer. Neither input‐output functions nor visual detection levels for tones from 0.125 through 16 kHz provided any evidence for low‐tone dysfunction in methylmercury‐treated subjects. Supranormal evoked response amplitudes were seen at 8 and 16 kHz. Contrary to earlier conclusions based only on morphological data, the guinea pig as a species appears to be an inappropriate model for methylmercury‐induced deafness reported in human victims.
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A model of binaural interaction (A)

Y. Sujaku, S. Kuwada, and T. C. T. Yin

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S90-S90 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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We present here a model which simulates some recent findings [S. Kuwada et al., Science 206, 586–588 (1979); S. Kuwada et al., Neurosci. Abstr. 76 (1979)] in which the interaural phase sensitivity of inferior colliculus neurons has been studied using interaural delays or binaural beats. The cyclic response patterns of some neurons are altered systematically as a function of stimulus off‐time and interaural intensity differences. In addition, the response to binaural beat stimuli indicates that some cells are sensitive to the direction of interaural phase change. The model is comprised of two inputs (one from each ear), each with crossed collateral inhibition. The two inputs synapse on a third cell, resulting in four synaptic connections; two inputs are presynaptic inhibitory and two are direct excitatory. At each junction, simple rules about transmitter release, transmitter supply, and changes in membrane potential are made. Manipulation of these parameters allows for simulation of the commonly seen cyclic response pattern as well as some of the unique effects of off‐time, interaural intensity differences, and sensitivity to a particular direction of interaural phase change. [Supported by NIH grant NS12732.
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Assessment of hearing sensitivity in normal newborns and adults using the slow negative scalp response at 10 ms (SN10) (A)

M. D. Hawes and H. J. Greenberg

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S91-S91 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The recently discovered slow negative brain stem response at 10 ms (SN10) was investigated as a tool for assessment of hearing sensitivity in 20 normal newborns and adults. Tone pips of 500, 1000, and 2000 Hz and a click were presented at 60, 40, and 20 dB re normal hearing level. The SN10 response varied systematically as a function of frequency and intensity. The SN10 response was not observable for all stimuli; however, percentages of detection improved as frequency and intensity increased. Newborns demonstrated significantly longer latencies than adults for all stimuli. Overall results suggested that SN10 is a reliable indicator of hearing sensitivity for frequencies of 1000 Hz and higher.
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Behavioral threshold for tones in 6‐ and 10‐month‐old infants (A)

Kathleen M. Berg and Melanie C. Smith

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S91-S91 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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Behavioral thresholds for 500, 2000, and 8000 Hz tone bursts were determined for 6‐ and 10‐month‐old human infants using a transformed up‐down tracking procedure in a conditioned head turn paradigm. In experiment 1, stimuli were presented in free field and tracking was initiated at an intensity well above threshold. For 10‐month‐old infants, threshold estimates were approximately 15 dB above adult values at all three frequencies. Six‐month‐old thresholds were slightly higher and relatively flat across frequencies. In experiment 2, stimuli were presented via earphone, tracking was initiated below threshold, and supra threshold probe trials were introduced to assess the infants' motivation to respond. With these changes in procedure, 6‐month‐olds showed the adult U‐shaped sensitivity function. [Work supported by NINCDS.]
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Hearing evaluation in families with familial hypercholesterolemia (A)

James H. Zavoral, David W. Johnson, and Donald W. Shrewsbury

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S91-S91 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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Hyperlipidemia has been implicated as a cause of sensorineural hearing loss. Forty‐five subjects (25 male, 20 female), age 6 to 57, from families with familial hypercholestcrolemia were prospectively evaluated with pure‐tone audiometrics (from 0.25 to 8 kHz) and serum lipoprotein quantification. Twenty had no lipid abnormality (N); 25 had familial hypercholesterolemia (FHC). All had clinically normal hearing and tympanometry. In 13 FHC and 11 N under 18, hearing at 6 and 8 kHz was reduced compared to age/sex adjusted values (NL) (p < 0.001). FHC compared to N were not significantly different. In 12 FHC and nine N over 18, there was reduced hearing compared to NL at selected frequencies. FHC vs N revealed reduced hearing in higher frequencies for males (3–8 kHz) (p < 0.01) and in lower frequencies for females (0.25–1 kHz) (p < 0.01). FHC and N from FHC families compared to NL had decreased hearing at selected frequencies at all ages. The difference between FHC and N was more pronounced in subjects over 18.
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Growth functions of the acoustic reflex recorded with a 660‐Hz probe (A)

D. J. Thompson, H. E. Gary, and L. Howington

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S91-S91 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The relationship between chronological age and acoustic reflex growth was examined in 30 female adults in the 20 to 79 years age range. Acoustic reflex activity was recorded contralaterally in acoustic conductance and acoustic susceptance (mmhos). Growth functions were generated with ascending series of stimuli presented in 1‐dB steps which began below the reflex threshold and were increased to 120 dB SPL. Four activating stimuli were used, three tones—500, 1000, and 2000 Hz—and a (high‐pass) filtered noise. Static acoustic emittance was computed and reflex thresholds were obtained. Growth expressed in conductance was commonly a decreasing monotonic function. Patterns of susceptance growth, which were more complex than conductance and contained diphasic reflex responses, were grouped into categories. Older subjects tended to produce a reduced rate of growth or a smaller magnitude of reflex response, in agreement with data reported for lower probe tones [D. J. Thompson, J. A. Sills, K. M. Recke, and D. M. Bui, “Acoustic reflex growth in the aging adult,” J. Speech Hear, Res. (in press)]. Growth data were also converted to acoustic resistance and acoustic reactante.
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Large‐scale check on the consistency of coupler threshold standards (A)

Edith L. R. Corliss

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S91-S91 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The Health and Nutrition Examination Survey (HANES), conducted by the US Public Health Service in 1971‐75, provided hearing data on a population sample of approximately 3000 individuals on whom both pure‐tone and speech audiometric measurements were made. All audiometers were equipped with TDH‐49 earphones with supra‐aural MX41/AR cushions. The speech test was used at the National Bureau of Standards to select normal individuals from HANES, and was a criterion essentially independent of the pure‐tone thresholds. For each individual earphone. The pure‐tone threshold data were referred to standard coupler pressures, taking into account the audiometer output pressures as calibrated weekly. Over this large group of earphones the thresholds obtained are uniform; this study thus verifies the logic of maintaining standard data for audiometric thresholds in terms of sound pressures produced in the calibrating coupler for each type of earphone. However, this extensive group of normal individuals yields threshold data differing significantly and systematically from the ANSI‐1969 Standard for Normal Threshold of Hearing. The situation warrants further study.
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Flat‐plate coupler calibration of circumaural audiometric and hi‐fi earphones (A)

B. Kruger, B. Solomon, and R. Cohen

J. Acoust. Soc. Am. Volume 67, Issue S1, pp. S91-S92 (1980); (2 pages)

Online Publication Date: 11 Aug 2005

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Circumaural earphones have been shown to provide improved coupling when compared with the standard supra‐aural audiometric earphone (TDH‐39,49; calibrated with a standard NBS 9A coupler) [E. Villchur, J. Acoust. Soc. Am. 48, 1387–1396 (1970); N. P. Erber, J. Acoust. Sec. Am. 44, 555–562 (1968)]. A standard coupler is needed for circumaural carphone calibration. A flat‐plate coupler has been designed for calibration of a circumaural earphone (Telephonics model 556) for hearing testing [P. L. Michael and G. R. Bienvenue, J. Acoust. Soc. Am. 66, 944–950 (1976)] and proposed as a standard coupler for circumaural calibration [J. Prout, ANSI S3.37, Working Group Draft (1979)]. The use of this flat‐plate coupler for calibration of circumaural earphones for audiometry (Telephonics model 556, Beltone Auraldome and Audicup, and Phonic Ear) and for hi‐fi listening (Sennheiser HD430, Koss VFR and HV1LC, and AKG 240) was studied systematically. Repeated intra and intertester comparisons, and control of earphone position suggested guidelines for reducing variations. The utility of this flat‐plate coupler as a means of checking stability of earphone frequency response is supported. Differences in earphone responses, effects of leakage, and resonances will be demonstrated and discussed. [Work partially supported by AOS.]
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