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Nov 1988

Volume 84, Issue S1, pp. S2-S224

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back to top Session AA. Physiological Acoustics VI and Psychological Acoustics III: Localization and Binaural Hearing (Poster Session)
Contributed Papers
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The Franssen effect and the localization plausibility hypothesis (A)

Brad Rakerd and William Morris Hartmann

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S79-S79 (1988); (1 page) | Cited 1 time

Online Publication Date: 13 Aug 2005

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The Franssen effect is obtained with two loudspeakers in a room. If a sine tone is abruptly turned on at the left loudspeaker, then slowly faded off while the right loudspeaker is slowly faded on, a listener will judge that the tone continues to come from the left loudspeaker, even though the left loudspeaker is not sounding at all. Our own studies of localization of sound in rooms have led to a principle of localization called the “plausibility hypothesis.” One of the predictions of this hypothesis is that in an anechoic room the Franssen effect should fail [B. Rakerd and W. M. Hartmann, J. Acoust. Soc. Am. 78, 524–533 (1985)]. Experimental studies are reported using the Franssen stimulus both in an ordinary room and in an anechoic room. The results of the experiment support the prediction. [Work supported by the National Institutes of Health.]
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Acoustic origins of individual differences in sound localization behavior (A)

Elizabeth Wenzel, Frederic Wightman, Doris Kistler, and Scott Foster

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S79-S79 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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Human listeners vary widely in their ability to localize unfamiliar sounds in an environment devoid of visual cues. Our research, in which blindfolded listeners give numerical estimates of apparent source azimuth and elevation, suggests that individual differences are greatest in judgments of source elevation; listeners are uniformly accurate when judging source azimuth. The pattern of individual differences is the same for free‐field sources and for simulated free‐field sources presented over head‐phones. Simulated free‐field sources are produced by digital filtering techniques which incorporate the listener‐specific, direction‐dependent acoustic effects of the outer ears. Two features of this data bear on the question of the origin of individual differences in elevation accuracy: (1) a listener's accuracy in judging source elevation can be predicted from an analysis of the acoustic characteristics of the listener's outer ears; (2) the pattern of elevation errors made by one listener (A) can be transferred to another listener (B) by presenting to listener B the simulated free‐field sources derived from the outer‐ear acoustics of listener A. Thus it is believed that many of the individual differences in localization behavior are traceable to individual differences in outer‐ear acoustics. The data have important implications for the study of localization in both basic and applied contexts. [Work supported by NASA, NSF, and USAF‐AAMRL‐AFSC.]
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Prefiltering method for a head‐related stereophonic system (A)

Takayuki Mizuuchi, Kaoru Okabe, Hareo Hamada, and Tanetoshi Miura

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S79-S79 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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The prefiltering scheme of the usual head‐related stereophonic system using two loudspeakers for reproduction [M. R. Schroeder et al., J. Acoust. Soc. Am. 56, 1195 (1974)] was modified. In addition to the usual filtering scheme, an additional filtering stage is introduced that converted the frontal incident characteristics of the dummy head into those for individual listeners. Using this filtering scheme, the exact reproduction of the frontal sound image becomes possible, which is difficult when the sound recorded through a dummy head is played back. The ability of this modified system to reproduce the original sound localization by a listening test in an anechoic chamber is evaluated. In the test, both the conventional scheme and the new one were evaluated. As a result, the localization of the frontal sound image was reproduced exactly using the new system, and the conventional system failed in this reproduction. It was also confirmed that sound from other directions in the three‐dimensional space was almost perfectly reproduced using the new system.
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Echo suppression or localization masking? (A)

Pierre L. Divenyi

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S79-S79 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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A brief dichotic conditioner (C) has been shown to effectively disrupt lateralization of a brief probe (P) presented after a short interval (4–7 ms, onset to onset) with an interaural time delay that is perfectly audible in the absence of the C [P. M. Zurek, J. Acoust. Soc. Am. 66, 1750–1757 (1980)], even when the C and the P are different sounds [P. L. Divenyi and J. Blauert, in Auditory Processing of Complex Sounds, edited by W. A. Yost and C. S. Watson (Erlbaum, Hillsdale, NJ, 1987), pp. 146–155]. An echo suppression mechanism responsible for this effect would predict (1) suppression to be strongest when the C and the P are identical and to decrease monotonically as the spectra of the two sounds are made different, and (2) a monotonic falloff of suppression when the temporal separation between the two sounds is increased beyond a certain minimum. In the present experiments, the effects of frequency separation and temporal separation between a narrow‐band P centered at 2 kHz and a C were systematically explored. Contrary to the predictions, low‐frequency (0.8 < 1.3 kHz) C's were more effective in suppressing the lateralization of the P than those closer to the P frequency, and lateralization performance was nonmonotonically related to temporal separation between C and P. The results suggest that a dichotic stimulus with a relatively high localization strength could “mask” the localization of another, subsequent dichotic stimulus. [Work supported by the Veterans Administration.]
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Dependence of interaural time relationships in the cat upon sound source direction and frequency (A)

J. E. Mind, A. D. Musicant, J. C. K. Chan, and R. K. Kochhar

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S80-S80 (1988); (1 page) | Cited 1 time

Online Publication Date: 13 Aug 2005

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Using a probe microphone surgically implanted near each eardrum of an anesthetized cat, the time waveform was recorded in both ears in response to a click as the azimuth and elevation of a loudspeaker were varied. Two forms of interaural time delay (ITD) were calculated. Arrival time (AT) for each ear was based upon the leading edge of the click waveform and the first measure of ITD was taken as the difference in AT for the two ears. The FFT analysis of the time waveforms also yielded the interaural phase difference (IPD) for the individual frequency components. The phase‐derived ITD was calculated as IPD/ω and enabled study of the dependence of ITD upon frequency. Both measures of ITD varied systematically with azimuth and elevation and reached values greater than would be expected from the interaural distance. Kuhn [Directional Hearing, edited by W. Yost and G. Gourevitch, (Springer, Berlin, 1987), Chap. 1] has shown for the human that ITDs for low and high frequencies are in the ratio of 3:2, respectively. The present study yields similar findings in the cat and confirms and extends earlier work.
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Lateralization predictions for high‐frequency binaural stimuli (A)

Richard M. Stern, Glenn D. Shear, and Torsten Zeppenfeld

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S80-S80 (1988); (1 page) | Cited 1 time

Online Publication Date: 13 Aug 2005

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The position‐variable model [R. M. Stern, Jr. and H. S. Colburn, J. Acoust. Soc. Am. 64, 127–140 (1978); G. D. Shear and R. M. Stern, J. Acoust. Soc. Am. Suppl. 1 81, S27 (1987)] is extended to describe the subjective lateral position of amplitude‐modulated tones and bandpass noise, as well as other complex stimuli that are presented within spectral regions at which the binaural system appears to be unable to make use of cycle‐by‐cycle interaural temporal differences. Predictions of the model are based on the centroid of the cross correlation of the hypothetical auditory‐nerve response to the stimuli, which is either calculated using analytical techniques or simulated numerically. The model of auditory‐nerve activity, which is typically used to describe the response to stimuli at lower frequencies, also extracts envelopes of higher frequency stimuli, as discussed previously by Colburn and Esquissaud. This information appears to be useful in predicting the lateral position of such high‐frequency stimuli. Preliminary results indicate that the model is able to describe most of the ways in which the laterality of high‐frequency binaural stimuli with low‐frequency envelopes depends on modulation frequency, carrier frequency, and other stimulus parameters. The model also predicts the relative salience of interaural temporal cues at different frequencies. [Work supported by NSF.]
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Detection and lateralization based on interaural temporal disparities: Time or phase? (A)

Leslie R. Bernstein and Constantine Trahiotis

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S80-S80 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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This presentation will address whether the binaural auditory system's sensitivity to interaural temporal disparities is more appropriately characterized as a sensitivity to physical differences, across the ears, of time or phase per se. In two recent studies [W. A. Yost and R. H. Dye, J. Acoust. Soc. Am. 83, 1846–1851 (1988); W. A. Yost, J. Acoust. Soc. Am. 70, 397–409 (1981)], Yost and Dye measured thresholds for detection of, and extent of, laterality produced by interaural temporal disparities of pure tones between 200 and 5000 Hz. Because performance in both tasks appeared to be constant across frequency for a given interaural phase difference rather than for a given interaural time difference, Yost and Dye argued that phase is the most appropriate independent variable. This notion is inconsistent with several other sets of data obtained with complex signals and with pure tones. Furthermore, the constraints that the processing of interaural phase per se imposes on modern cross‐correlation‐based models of binaural hearing stand in contrast to the more parsimonious explanations based on interaural time.
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Transient latency in masking level difference (A)

Hisashi Kado, Shigeru Chiba, Kohzo Ohta, Hajime Miura, and Masaaki Fukumoto

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S80-S80 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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The threshold was measured for a signal S0 of 100 ms long at various timing points in a noise burst by a sequential searching procedure. The noise burst lasted from t = −1000 ms to t = 1000 ms. At t = 0 ms, the noise was changed from N0 to Nπ. The threshold was expected to decrease just after t = 0 ms. The latency was defined as a time constant of the decreasing characteristic of the threshold. In the case of S0 being a pure tone, the results showed artifacts at the N0 area and it was hard to define the latency. In the case of S0 being a vowel (female /a/, /i/ and male /i/), the latency was about 100 ms when subjects were required to identify the signal, and the latency was about 10 ms when subjects were required to detect the signal. The equalization and cancellation model could not explain the 10‐ms latency, because it is not reasonable to assume such fast feedback in the model. It is speculated that both the addition and subtraction of dichotic and/or diotic signals are sent to a higher level of the hearing system in such fast latency.
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Discrimination of the orientation of a natural sound source (A)

Pamela Zerne, David Perrott, John Cote, and Charles Lira

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S80-S80 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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The ability to discriminate the direction that a speaking individual is facing (i.e., toward, away, to the right, or to the left relative to the listener) was explored in a free‐field environment under monaural and binaural listening conditions with relative distances ranging between 1.5–12.0 m. All sessions were conducted under double‐blind conditions. Performance under binaural conditions clearly exceeded chance at all orientations and distances. The ability to resolve that the speaker was facing right or left was significantly impaired when binaural cues were eliminated. This surprising ability to resolve the relative orientation of a human speaker in the right‐left dimension cannot readily be explained by current theories of auditory spatial processes. [Work supported by NSF and NIH.]
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Utilization of spatially correlated auditory information in localization of visual targets (A)

Kourosh Saberi, David R. Perrott, and Sandra M. Pacheco

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S80-S80 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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Facilitation of a visual search task through presentation of spatially correlated and uncorrelated binaural and monaural cues was determined for five subjects using a two‐alternative, forced‐choice paradigm. Trains of 10‐ms clicks were spatially correlated with a visual target (0.496° visual angle) randomly located in a ±120° azimuth ±46° vertical spherical visual field and presented to subjects in two conditions (0°, ±46° vertical). Visual search time was also determined for monaural conditions in the ±46° vertical ±120° azimuth paradigm. Results indicate a dramatic reduction in search time for spatially correlated cues from approximately 15% at 0° to 40% at ±120° azimuth in the 0° elevated condition, and from 35% at 0° to 50% at ±120° azimuth in the ±46° elevated condition. The search time function for the monaural condition is surprisingly more similar to that of the spatially correlated binaural one, particularly in the center regions. Data indicate that loss of search time at the periphery in the uncorrelated condition is mostly due to the search strategy employed and not head movement delays. Practical implications will be discussed. [Work supported by NSF and NIH.]
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Minimum audible movement angle thresholds for broadband noise: Effects of the initial location of the source (A)

David R. Perrott, Carol L. Manligas, and Sandra Pacheco

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S80-S81 (1988); (2 pages)

Online Publication Date: 13 Aug 2005

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Minimum audible movement angle (MAMA) thresholds were determined for a source producing a broadband noise (500–8000 Hz) moving at a constant angular velocity (20°/s). Nine regions of the field were sampled: 0°, 10°, 20°, 40°, and 80° to the subject's right and left. In agreement with earlier research that employed either static sources or “simulated motion,” acuity was best when the source was at 0° azimuth (1.1°) and poorest at the most lateral position (3.1°–3.5°). The ability to detect motion of a source emitting a broadband noise is clearly superior to performance obtained with tonal signals whether the latter paradigms include “actual” or “simulated” motion. In the more extreme lateral regions of the field, performance was actually better than that previously reported under static localization conditions. Vertical azimuths, ranging from 0°–87.5°, were also examined. Detection of motion was relatively insensitive to this latter parameter. [Work supported by NSF and NIH.]
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Rotating tones and minimum audible movement angle (A)

David R. Perrott and B. Meier

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S81-S81 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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Minimum audible movement angle (MAMA) thresholds were determined for four subjects using a two‐alternative, forced‐choice adaptive paradigm. The motion was simulated by presenting a 200 to 1500‐Hz tone (f0) to one ear and a second tone (f0) of a different frequency to the other ear. With interaural frequency differences (IFD) of 0.5 Hz, and f0 at or below 600 Hz, MAMA thresholds ranged between 10°–15°. Additional tests conducted in this frequency region indicate that the continuous shifts in phase generated by small IFDs produce performance in excellent agreement with those obtained in free‐field localization tasks in which real and simulated motion has been considered. However, thresholds increase very rapidly at higher frequencies (e.g., MAMA exceeds 80° with an f0 of 850 Hz). There appears to be little agreement between the current “dichotic” rotating tone paradigm and other motion discrimination functions at these higher frequencies. The implications of these results will be discussed. [Work supported by NSF and NIH.]
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Click lateralization by multiple sclerosis patients (A)

Miriam Furst, Sara Eyal, and Amos D. Korczyn

J. Acoust. Soc. Am. Volume 84, Issue S1, pp. S81-S81 (1988); (1 page)

Online Publication Date: 13 Aug 2005

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Lateralization of dichotic clicks can be tested with gradually increasing interaural level differences (ILD) and interaural time differences (ITD). However, the lateralization of dichotic clicks with ITD is limited to small ITDS only (< 1 ms). The ability to lateralize dichotic clicks was tested in multiple sclerosis (MS) patients with normal audiograms. Two kinds of psychoacoustical experiments were employed: (1) a matching experiment in which the subject was asked to match the perceived positions of two click trains, where one included dichotic clicks with ILD and the other included dichotic clicks with ITD; (2) a positional jnd experiment in which the subject was asked to determine the difference in position of two successive click trains. Two reference positions were tested, the head center (ITD = 0 and ILD = 0) and midway between the center and the ear (ITD = 0.8 ms and ILD = 0 or ILD = 20 dB and ITD = 0). For each reference the experiment was performed first with control on ITD and then with control on ILD. From a group of 15 MS patients, seven performed poorly in the positional jnd experiment when the control was on ITD, and normally when the control was on ILD. Those subjects also reported that the position of each dichotic click with ITD < 1 ms was perceived at the head center, and, therefore, they had difficulties in performing the matching experiment. Brainstem auditory potentials (BAP) evoked by dichotic clicks with different ILDs and ITDs were measured in all the above MS patients. Principal component analysis of the measured waveforms indicates an abnormal behavior as a function of ITD in patients who performed abnormally in the psychoacoustical experiments. The anaylsis of the waveforms of all patients as a function of ILD resembles the normal behavior.
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