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May 1990

Volume 87, Issue S1, pp. S1-S164

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back to top Session FFF. Psychological Acoustics VIII: Audiometry and Related Issues; Auditory Brain‐stem Responses
Contributed Papers
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Investigation of headphones suitable for psychophysical experiments (A)

Tatsuya Hirahara and Kazuo Ueda

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S142-S142 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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In order to find the appropriate headphone to use in psychophysical experiments, the frequency responses of 12 headphones were measured by three physical methods: on an IEC coupler (B&K 4134), on a C coupler attached to a head and torso simulator (Kohken SAMRAI) (Okabe et al., J. Acoust. Soc. Jpn. (E) 5, 95–104), and by using a probe microphone in real ears. The results showed that very few electrostatic circumaural headphones (e.g., STAX SR‐Lambda Pro.) have relatively flat frequency characteristics, with excellent invariance among the measuring methods. In contrast, many dynamic supraaural headphones (e.g., Rion AD02, Beyer DT48, Elega DR831, etc.) have poor frequency characteristics, especially at lower frequencies, with many differences occurring between the three measuring methods. For these headphones, the energy leakage at the lower frequency region is inevitable, since the headphone pad fitting to the pinna is usually incomplete, and acoustic impedance of the diaphragm is very high. These undesirable characteristics might affect the results obtained in psychophysical experiments. As an example, results were severely affected by headphone differences in the vowel identification test using several synthesized vowels where the F0 component amplitude was manipulated. The physically determined frequency responses were compared with those from a psychophysical loudness matching procedure [K. Ueda and T. Hirahara, J. Acoust. Soc. Am. Suppl. 1 87, S142 (1990)].
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Frequency response of headphones measured in free field and diffuse field by loudness comparison (A)

Kazuo Ueda and Tatsuya Hirahara

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S142-S142 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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Coupler measurement of headphone frequency response may be incorrect at high and low frequencies [T. Hirahara and K. Ueda, J. Acoust. Soc. Am. Suppl. 1 87, S142 (1990)]. Since sound pressure near the eardrum is difficult to measure physically, a psychophysical method was employed to assess real ear frequency response of headphones. Loudness comparisons were performed by four subjects, under two experimental conditions: free field (anechoic room) and diffuse field (reverberation room). These conditions were run to check the influence of field characteristics on the reliability of the measurements. Each subject adjusted the headphone level of critical band noise bursts until they were equally loud as those from a reference loudspeaker (7 dB SPL). Measurement scatter was smaller in the diffuse field than in the free field. One hypothesis to explain this result is that head movement causes less change in level in a diffuse field than in a free field. Support for this comes from measurement of the SPL distribution in the two rooms, which revealed that the sound‐pressure variation was smaller in the diffuse field than in the free field. To examine the reliability of loudness judgments at high frequencies, another method—hearing thresholds by Békésy tracking—was employed. Each subject's threshold was measured with both loudspeakers and headphones. After compensation was made for loudspeaker transfer functions, headphone frequency response was deduced from the results. This method led to high‐frequency responses similar to those from loudness comparison. Below 6 kHz, however, there were only slight differences, because equating loudness for loudspeaker sound and for headphone sound does not strictly correspond to equal sound pressure at the eardrum.
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Equivalent threshold levels for TDH‐49 earphones and ER‐3A insert earphones (A)

Vickie F. Goran and Tom Frank

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S142-S142 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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Equivalent threshold sound‐pressure levels were obtained for 24 normally hearing adult subjects from 125 to 8000 Hz using TDH‐49 earphones in P/N 51 cushions and ER‐3A insert earphones having a modified foam earplug inserted into the ear canal so that the outer edge was flush with the floor of the concha. Test versus retest thresholds within and across test sessions were not clinically significant for each earphone type at each frequency. The threshold difference between the TDH‐49 and ER‐3A and the ER‐3A threshold levels at each frequency, referenced to an HA‐1 (2‐cc) coupler, were in very good agreement with the ER‐3A proposed reference threshold sound‐pressure levels at each frequency as reported by Wilber et al. [J. Acoust. Soc. Am. 83, 669–679 (1988)].
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Attenuation provided by audiometric earphones (A)

Vickie F. Goran and Tom Frank

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S142-S142 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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The attenuation provided by TDH‐49 earphones in P/N 51 cushions and ER‐3A insert earphones using modified foam earplugs was determined for 24 subjects using a real‐ear attenuation at threshold paradigm (ANSI S3.12‐1984). The TDH‐49 earphones were fitted on each subject as normally done for audiometry and the ER‐3A earplugs were inserted into each subject's ear canals so that the outer edge was flush with the floor of the concha. Compared with the TDH‐49, the ER‐3A provided about 18 dB more attenuation for the lower (125–500 Hz) and about 15 dB more attenuation for the higher (1000–8000 Hz) frequencies. Implications concerning the use of TDH‐type earphones and ER‐3A insert earphones in reference to permissible ambient noise levels for audiometry (ANSI S3.1‐1977) will be discussed.
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Attenuation characteristics of audiometric earphones fitted on children (A)

Diana C. Wright, Mark E. Bigger, and Tom Frank

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S143-S143 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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The attenuation provided by TDH‐49 earphones and ER‐3A insert earphones was determined for 20 children (5–14 years old) using one‐third octave bands of noise in a diffuse sound field (re: ANSI S12.6‐1984). The TDH‐49 earphones in P/N 51 cushions were fitted on each subject as normally done for audiometry. For the ER‐3A, an appropriate size (small or normal) modified foam earplug was inserted into each subject's ear canal so that the outer edge was flush with the floor of the concha. The attenuation provided by the ER‐3A was considerably greater than the TDH‐49 at each frequency regardless of earplug size. Further, the attenuation provided by the ER‐3A using the small (N = 10) or normal (N = 10) size modified foam earplug was similar. Comparisons with the attenuation provided by the TDH‐49 and ER‐3A using adult subjects and clinical implications relative to permissible ambient noise levels for audiometry will be discussed.
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Bone conduction thresholds for different mastoid placement sites (A)

Diana C. Wright and Tom Frank

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S143-S143 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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Bone conduction thresholds were obtained from 250 to 4000 Hz by placing the bone vibrator on the mastoid as done for audiometry and at mastoid sites initially judged to produce the loudest perception of a 250‐, 500‐, and 1000‐Hz pure tone and white noise using 30 normally hearing adult subjects. The bone conduction thresholds were found to be variable across placement sites and test frequencies. However, the placement site judged to be the loudest with white noise generally resulted in the lowest thresholds. Implications for bone conduction audiometry, including normal air‐bone gaps, and reference equivalent threshold force levels will be discussed.
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Bone conduction clicks and related observations (A)

John D. Durrant, Rick Hyre, and Walter W. Piroth

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S143-S143 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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The frequency responses of bone vibrators, as measured on the artificial mastoid, and earphones, as measured on a 6‐cc coupler, predict substantial differences in bone (BC) and air conduction (AC) clicks, which are evident perceptually. Since clicks continue to be used widely in clinical evaluations of brain‐stem auditory evoked potentials (BAEPs), it seemed worthwhile to assess the effective frequency response of standard BC versus AC transducers. Steady‐state stimuli were first used in a modified version of the SAL test. Although BC and AC differences were evident, they were not as great as suggested by coupler and artificial‐mastoid measurements. In the same subjects, skull vibration was examined in response to BC clicks, using a miniature accelerometer. The results demonstrate propagationlike delays in BC stimuli applied and monitored at different points on the skull. Implications for BAEP measurement, utilizing BC click stimulation, are presented (supplemented by samples of recordings) and suggest greater similarities than differences in BC versus AC clicks. [Work supported by Ben Franklin Partnership, Commonwealth of Pennsylvania and Radioear Corporation.]
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Influence of contralateral noise stimulation on wave I of the ABR, elicited with condensation and rarefaction clicks in humans (A)

Vishakha W. Rawool, John M. Heinz, and Joseph P. Pillion

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S143-S143 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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Sound‐evoked efferent effects can be examined by comparing the response amplitudes of the auditory nerve with and without contralateral stimulation. It has been suggested that the efferent system modifies the mechanical characteristics of the cochlear partition by varying outer hair cell tonus and regulating the mean position of the basilar membrane [E. L. LePage, Hear. Res. 38, 177–198 (1989)]. If this is the case, the effect of contralateral stimulation may be different for responses elicited with clicks of opposite polarity (condensation versus rarefaction), as such stimuli cause initial movement of the basilar membrane either toward scala tympani or scala vestibuli. Furthermore, such stimuli are known to elicit dissimilar ABR waveforms [V. Rawool and S. Zerlin, Stand. Audiol. 17 (1988)]. Results of the surface recorded wave of the ABR obtained from human subjects, with and without contralateral noise, for rarefaction and condensation clicks as well as the possible underlying mechanisms will be presented.
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Repeated‐measures auditory brain‐stem responses (ABRs): Comparisons of stability profiles based on different time schedules (A)

Judith L. Lauter and Jan Lord‐Maes

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S143-S143 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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Demonstrations of dramatically increased information from ABRs based on variability analysis [J. L. Lauter and R. L. Loomis, Scand. Audiol. 15, 167–172 (1986); 17, 87–92 (1988); J. L. Lauter and R. G. Karzon, Scand. Audiol. (in press)] have to date all been based on within‐subject series of weekly test sessions. Toward making repeated‐measures EPs more feasible as a research and clinical tool, the current experiment compares ABR stability profiles based on different test schedules: four waveforms per ear of presentation collected from each subject with (1) minimal separation between ear sets (i.e., four right‐ear, left‐ear, and binaural waveforms, all collected within the same 1‐h session), (2) 1‐h separation between ear sets, and (3) 1‐week separation between ear sets. Results to date indicate (1) very good matches between stability profiles based on same‐session versus weekly collections, validating an earlier claim that these profiles reflect real individual characteristics; and (2) distinctions between profiles from these two schedules versus the hourly collections, possibly reflecting the influence of diurnal variations in ABRs reported by earlier research [Kerkhof et al., Neurosci. Lett. 16, 11–15 (1980)]. [Work supported by AFOSR.]
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Field potentials in rat brain stem during binaural acoustic stimulation (A)

Roger P. Gaumond

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S143-S144 (1990); (2 pages)

Online Publication Date: 13 Aug 2005

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Electric field potentials were measured in rat brain stem while presenting monaural or binaural acoustic click stimuli. The binaural difference (BD) potential, defined as the sum of field potentials due to menaural stimuli minus that due to a binaural stimulus, was recorded at 1‐mm intervals along a track passing through the inferior colliculus and the superior olivary nuclei. Scalp surface potentials were recorded simultaneously. Prominent BD potentials were observed at all intracranial locations. Scalp surface BD was contemporaneous with an intracranial BD waveform that reversed sign at a level midway between the inferior colliculus and the olivary nuclei. The onset of BD potentials at or below this level occurs 1 ms after the appearance of prominent monaural and binaural response waveforms. This latency difference suggests the existence of an additional synapse in the pathway leading to the structure responsible for BD generation compared to pathways leading to other structures in the superior olivary complex. [Work supported by Penn Lions Hearing Research Foundation.]
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