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May 1983

Volume 73, Issue S1, pp. S1-S106

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back to top Session CC. Physiological Acoustics IV: Auditory System Function and Response Activity
Contributed Papers
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How do we measure hearing by bone conduction? (A)

Edith L. R. Corliss and Shyam M. Khanna

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S59-S59 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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Measurements of the threshold of hearing by bone conduction are made clinically by the use of a driver calibrated upon an artificial mastoid. The driver is calibrated for its voltage response. Normalization data have been obtained by a number of investigators with groups of young adults in terms of force, displacement, and acceleration. This paper discusses the relationship between these norms and the stimulus presented at the otic capsule. The paper discusses the physical factors leading to variability: the head, the driver, and the mechanical coupling between them. Given the problems observed, the force stimulus eliciting threshold sensation is probably the most reliable quantity to measure, and the simplest to calibrate.
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The bone‐anchored bearing aid, a study of the mechanical point impedance of the buman head with and without skin penetration (A)

Bo Håkansson and Anders Tjellström

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S59-S59 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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The possibility of implanting a skin penetrating titanium screw into the mastoid portion of human skull and of establishing a permanent reaction‐free skin penetration has made it possible to develop and attach a new bone conduction hearing aid directly to the skull. To understand and improve this new hearing system, the mechanical point impedance of the titanium screw‐skull system ZMT has been measured. The conventional point impedance of the skin‐covered mastoid portion of the temporal bone ZMS has also been measured and the difference in magnitude between the two impedances, 2010 log ∣ZMT/ZMS∣, was calculated. Seven patients have been investigated. The magnitudes of ZMT were found to be between 10 and 35 dB higher than those of ZMS. One conclusion is that the conventional point impedance of the skin‐covered mastoid portion of the skull is essentially due to the properties of the skin and subcutaneous soft tissues. Another conclusion is that much lower velocity levels are needed, with skin penetration, for a given hearing sensation, which makes it possible to develop an “all in one housing” bone‐conduction hearing aid.
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Short‐latency auditory‐evoked response thresholds in infants and adults (A)

Alan J. Klein

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S59-S59 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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Auditory‐evoked potential thresholds were measured on a group of normal‐hearing adults and on a group of healthy infants without any history of middle‐ear disease. Acoustic stimuli were computer generated tone pips with frequencies of 500 Hz, 4 kHz, and 10 kHz. For 500‐Hz stimuli, presentation rate was 40/s and bioelectric activity was filtered at 60–2000 Hz in order to optimally record wave V of the BSR. Mean evoked potential thresholds in adults are 10–15 dB higher than behavioral thresholds to the identical stimuli. Preliminary results from infants less than 8 months old suggest evoked response thresholds are similar to adults at high frequencies. Large intersubject variability at 500 Hz confound threshold comparisons at this time.
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Evaluation of a microprocessor‐based, 40‐Hz ERP system (A)

James M. Lynn, Sharon A. Lesner, Cynthia C. Daddario, and Lynn Wood

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S59-S59 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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Galambos et al. [Proc. Natl. Acad. Sci USA 78, 2643 (1981)] described a procedure for recording the auditory middle‐latency response potentials which they named the 40‐Hz event‐related potential (40‐Hz ERP). Galambos and Makeig [J. Acoust. Soc. Am. Suppl. 1 72, S54 (1982)] recently have suggested that since the 40‐Hz ERP resembles a sine wave, cross‐correlation techniques can be used to identify the presence of a response and should, therefore, yield accurate threshold estimations. Axionics Instruments has developed a microprocessor‐based evoked potential system, called AUDIT, that estimates 40‐Hz ERP with a similar procedure. Results of an investigation of the predicative accuracy of AUDIT will be reported. Estimates of the hearing sensitivity of 25 adult hearing‐impaired subjects for 500‐, 1000‐, and 2000‐Hz signals based on AUDIT data will be compared to behavioral pure‐tone audiograms.
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An electroencephalographic evoked response correlate of auditory adaptation (A)

Ronald L. Cohen and Ernest M. Weiler

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S59-S59 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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Normal‐hearing subjects were evaluated to determine whether changes in behavioral auditory thresholds, in both a heterophonic and homophonic listening condition, would produce equal two dissimilar changes in the amplitude and latency of the auditory evoked potential. Each subject completed a preadaptation loudness balance prior to any stimulation. A 2000‐Hz pure tone was then presented to the subject's right ear for a period of 7 min at a level of 60 dB SPL. During this 7‐min adapting period four AER runs consisting of 32 tone pips superimposed on the adapting tone were presented. Finally, a perstimulatory loudness balance was completed while the adapting tone had been on for 7 min. Measurements of amplitude and latency of the evoked potentials were analyzed and results suggest that more adaptation occurred for the homophonic condition. However, a significant amount of decrement in the amplitude of the monaurally elicited AER was measured for both the homophonic and heterophonic condition. It was suggested that AER may be a sensitive measurement technique of auditory adaptation.
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Sound pressure distribution in the human ear canal (A)

M. R. Stinson and E. A. G. Shaw

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S59-S60 (1983); (2 pages)

Online Publication Date: 12 Aug 2005

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The geometry of the human ear canal differs considerably from its conventional description as a uniform cylinder with a plane perpendicular end. The differences can be expected to produce significant effects especially at frequencies greater than 10 kHz. Measurements of sound pressure distribution within an accurately scaled (×2.5) replica of a real ear canal confirm the effects of the tapered end observed previously in simple models [J. Acoust. Soc. Am. Suppl. 1 71, S88 (1982)] and show that the standing wave patterns in the main body of the canal are appreciably disturbed. In agreement with the earlier work, the variations in SPL across the human eardrum must be expected to exceed 15 dB at 15 kHz. An approximate theory has been developed to describe the sound field within ear canals of varying cross section and direction. The theory is an extension of Webster's horn equation, quantifying the canal geometry using effective cross‐sectional areas defined along an appropriate curved axis. Agreement between theoretical and experimental pressure distributions is good.
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Simulator investigation of the effects of occluded ear characteristics on remote measurement of eardrum SPL (A)

Samuel Gilman, Donald Dirks, and David G. Hanson

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S60-S60 (1983); (1 page) | Cited 1 time

Online Publication Date: 12 Aug 2005

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Because of developments in remote measurement of eardrum sound pressure level (SPL) in hearing aid occluded ears, an investigation was made of the effects of external ear characteristics on such measurements. Two systems were investigated: a probe microphone contained within the earmold, and a miniature microphone in the ear canal located as close as possible to the medial end of the earmold. Ear stimulators (ANSI S3.25‐1979) were modified to have a range of eardrum impedances approximating 96% of the population with normal middle ears [Zwislocki and Feldman, ASHA Monogr. No. 15 (1970)] in three steps and to have a range of ear canal lengths of 9.7 to 17.7 mm in four steps. SPL measurements were made over a frequency range of 0.2 to 6 kHz for each combination of length and impedance. As predicted by transmission line calculations, both ear canal length and eardrum impedance affected the measured SPL. Although individual measurements made by each system differed somewhat because of differences in measurement location, the total range of differences between measured and actual eardrum SPL was almost identical for both systems. With optimum calibration in an ear simulator, the maximum error produced by either system was within ±5 dB of the true eardrum SPL.
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Correlates of acoustic reflex latency in normal‐hearing adults of two age groups (A)

M. Hannley and G. Ray

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S60-S60 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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Parametric studies of the acoustic stapedial reflex may be made by measuring its threshold, amplitude, and time course, including latency. Previous reports have established that aging affects the acoustic reflex in at least two ways: by raising its threshold to noise and tone activators; and by reducing the amplitude. In this study, we compared acoustic reflex latency in females of two age groups, 20–40 years and 60–80 years, when the activator tone was presented at equal sound pressure level (SPL), at equal sensation level (SL), and when reflex amplitudes were matched. The results indicated that acoustic reflex latency can be predicted more reliably on the basis of amplitude than on absolute or relative levels of the activator signal. Implications of these findings to the use of latency measures as indicants of central auditory dysfunction are discussed.
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Human auditory cortex: A preliminary report on studies using positron emission tomography (PET) (A)

Judith L. Lauter, Marcus E. Raichle, and Peter Herscovitch

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S60-S60 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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In recent years information has been gathered regarding the organization of auditory pathways in nonhuman subjects. However, because of the invasive nature of current techniques for studying the central nervous system, there is little direct measurement of central auditory processes in humans. Positron emission tomography (PET), used to monitor changes in cerebral blood flow and metabolism, offers a relatively noninvasive technique that may allow us to observe brain responses in humans to auditory and other sensory stimulation. We have studied a number of young normal volunteers, combining the PET technique with controlled auditory stimulation. Examination of PET images of cerebral blood flow before, during, and after stimulation (including monaural and binaural presentation of a variety of tones and noises) indicates that discrete, highly localized changes in cerebral blood flow can be evoked with such stimulation. A number of acoustical variables seem to influence these changes, including sound spectrum, rate and level of presentation, and ear of input.
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Pathological sensitivity enhancement in the tails of neuronal tuning curves—A possible explanation (A)

J. J. Zwislocki

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S60-S60 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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In many pathological cochleas the tips of the tuning curves of cochlear nerve afferents are desensitized, but the tails are sensitized. This apparent paradox can be explained through likely micromechanical events in the organ of Corti. If the excitation of the inner hair cells is due to shear motion between the reticular lamina and the tectorial membrane, and the tectorial membrane can vibrate in two modes—parallel and nearly orthogonal to basilar‐membrane motion—both the amplitude and phase of the hair‐cell excitation at the tail frequencies can vary over a wide range. This is so because, as we have shown in the past, the amplitude of the radial vibration of the tectorial membrane at the location of the inner hair cells may be nearly equal to that of the reticular lamina, leading to a vanishing shear motion between them. When the mechanical coupling between the organ of Corti and the tectorial membrane is weakened pathologically, the tectorial‐membrane amplitude should be decreased and the shear motion enhanced with the resulting enhancement of the hair‐cell excitation. [Work supported by NIH.]
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Time course of suppression of spontaneous otoacoustic emissions (A)

Mario A. Ruggero and Nola C. Rich

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S60-S60 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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Few data are available on the time course of suppression, by externally introduced sounds, of spontaneous otoacoustic emissions (SOAEs), and none have been presented for humans. By means of extensive averaging in the time domain and digital filtering, we have obtained such data for the (synchronized) SOAE produced by the first author's right ear (7529 Hz, 10–16 dB SPL). Upon presentation of a tone pip, there is a latency (1.2 ms at high suppressor levels, longer at lower levels) before any change can be detected in SOAE level. Most of the suppression then develops over an interval lasting 1.5–2.0 ms, but this relatively fast onset is followed by a roughly exponential slope with a time constant longer than 4 ms. At low suppressor levels, the latency to the beginning of recovery from suppression may be similar to the latency to suppression onset; for higher suppressor levels, the latency may be several tens of ms and recovery may not be complete before 100 ms. Given the uncertainty that still exists on travel times in the human basilar membrane, our data cannot rule out the possibility that the latency to onset of suppression matches the travel time in the cochlea to and from the site of origin of the SOAE. [Work supported by NIH Grant NS‐12125.]
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Tobramycin‐induced hearing loss in a patient with end‐stage renal disease (A)

David W. Johnson, Gary Matzke, David Anderson, Charles Halstenson, Paul A. Abraham, and William F. Keane

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S60-S61 (1983); (2 pages)

Online Publication Date: 12 Aug 2005

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A 60‐year‐old female undergoing chronic hemodialysis for end‐stage renal disease was evaluated audiologically for the frequencies 0.25, 0.5, 1, 2, 3, 4, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 kHz over a 7‐week period during and after a 4‐week course of tobramycin used for control of diverticulitis. Blood levels of the medication were monitored serially and pre‐ and post‐hemodialysis. BAR audiometrics were administered periodically over the 7‐week period. Despite conservative medical management where blood levels of medication were allowed to peak at 7 mcg/ml concentration and trough at 2 mcg/ml, the patient demonstrated progressive hearing loss which commenced in the extended high tones and progressively affected lower tone acuity. By the completion of the 7‐week period, 6 and 8 kHz were just beginning to show decrease in hearing function while lower primary speech frequencies remained unaffected. BAR data demonstrated no overt changes in wave latencies. Other BAR findings and blood studies were explored with respect to hearing loss findings.
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External ear effects during early development in the kitten (A)

Edward J. Walsh, JoAnn McGee, and Eric Javel

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S61-S61 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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At birth, the auditory system of the kitten is grossly immature; however, during the first ten postnatal days the external ear becomes patent, the middle‐ear cavity clears, ossicular calcification progresses, and the cochlea differentiates. The effect of the closed external ear as an attenuator during early maturation was measured using auditory brainstem evoked response (ABR) comparisons between operated and intact animals. Kittens were anesthetized and the external ear was resected to the level of the tympanic annulus exposing the tympanum. Using equal intensity stimuli, ABRs recorded from operated animals were observed as early as the second postnatal day, about six days earlier than from intact animals. The frequency range over which responses occurred was smaller than the range exhibited in older animals. Attenuation effects of 10 to 20 dB were observed in the mid‐to‐low frequency range; however, above 2.0 kHz high thresholds (120 dB SPL) precluded our ability to elicit responses in the intact animal. Thus, although external ear attenuation effects were observed, the immaturity of the system during the first postnatal week minimized its effect, particularly for frequencies above 2.0 kHz. [Work supported by NINCDS.]
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Topographic organization of interaural‐intensity‐difference sensitivity in deep superior colliculus (A)

Lisa Z. Wise and Dexter R. F. Irvine

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S61-S61 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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The sensitivity to interaural intensity differences (IIDs) of acoustically responsive neurons was examined in multiple microelectrode penetrations along the rostro‐caudal axis of deep superior colliculus (SC) in anesthetized cats. The most rostrally located neurons were unresponsive to monaural stimulation but were strongly excited binaurally. IID sensitivity functions for these “predominantly binaural” (PB) neurons were sharply peaked with maximum response at or near zero IID. Caudal to the PB cell area, most neurons were excited by contralateral stimulation and inhibited by ipsilateral stimulation (EI cells). All EI cells were maximally excited over a range of IIDs favoring the contralateral ear and were totally inhibited over a range favoring the ipsilateral ear. The position of the cutoff between excitatory and inhibitory regions was located near zero IID (corresponding to the median plane) for the most rostrally located EI neurons and was shifted progressively to IIDs favoring the contralateral ear (corresponding to increasing contralateral azimuths) for more caudally located EI neurons. The consequence of this topography is that IID, and hence azimuthal location, is represented by the extent of deep SC activated.
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ABR multielectrode recording: Determination of source position movement through cat brainstem (A)

R. P. Gaumond

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S61-S61 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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The click‐evoked acoustic brainstem response (ABR), average of 512 responses, was recorded at 18 sites on the scalp of anesthetized cats. Scalp recordings were used to determine source position by attributing the scalp‐surface potential field at each instant to the presence of a single current‐dipole equivalent source, immersed within a spherical, homogeneous volume conductor. At each sampling instant, equivalent source position was determined by the method of Schneider [IEEE Trans. BME‐21, 52–54 (1974)]. At those instants corresponding to vertex‐positive response peaks, the single‐source model was generally consistent with observed field patterns. Plots of equivalent source position along the axis from head center through vertex between 2.5 and 6.0 ms following the click. Movement along other axes is less prominent. Lack of movement along the centro‐lateral axis may reflect the activity of sources arrayed symmetrically along either side of the brainstem, while the lack of expected ventral movement is attributed to limitations of the spherical head model assumed. [Work supported by the Whitaker Foundation.]
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