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Apr 1982

Volume 71, Issue S1, pp. S1-S113

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back to top Session QQ. Psychological Acoustics V: Lateralization and Localization
Contributed Papers
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Detectability of interaural phase shift as a function of frequency (A)

Hans Kunov and Sharon M. Abel

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S86-S86 (1982); (1 page)

Online Publication Date: 12 Aug 2005

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Previous research [S. M. Abel and H. Kunov, J. Acoust. Soc. Am. Suppl. 1 69, S63 (1981)] indicated that the envelope cue contributed by rise/decay (R/D) of sinusoidal signals had little effect above 1500 Hz but affected lateralization below 1250 Hz. The relationship between R/D and frequency was studied in detail. Binaural signals were presented 180° out of phase, and the entire signal was delayed randomly to the left or right ear. Plots of P(C) versus the reciprocal of R/D on normal probability paper indicate a linear relationship between 20 and 700 ms. The slopes show that the use of the envelope cue peaks at approximately 1000 Hz, falling to near 0 before 2000 Hz. In a subsequent experiment, using R/D sufficiently long (700 ms) to eliminate the envelope cue, the effect of frequency on phase detection was examined, especially between 1200 and 1700 Hz. Psychometric functions were determined for interaural phase shifts (θ) close to 0° and 180°. At 1000 Hz, their slopes were approximately 8 %/deg and −2 %/deg, respectively, both falling linearly to 0 around 1600 Hz. The data from these two experiments provide quantification of the use of envelope and phase cues with frequency.
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Interaural intensity discrimination of noise as a function of center frequency, duration, and interaural correlation (A)

D. Wesley Grantham and Jayne B. Ahlstrom

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S86-S87 (1982); (2 pages)

Online Publication Date: 12 Aug 2005

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Interaural intensity difference thresholds were determined for three bands of Gaussian noise: a wideband noise (100–5000 Hz) and two 0.4‐octave narrow bands (48 dB/octave skirts) centered at 500 and 4000 Hz. Thresholds were estimated from psychometric functions generated employing a two‐interval forced‐choice blocked procedure, in which the nominal interaural intensity difference on each trial was divided between the two ears. Reference intensity was 70 dB SPL (overall). StimUlus duration (30 or 500 ms) and interaural correlation of the noise (0.0 or 1.0) were parametrically varied. For the 500‐ms stimulus durations thresholds were near 1 dB (½‐dB change in either ear alone) for all types of noise and for the two values of interaural correlation employed. For the briefer (30 ms) stimuli thresholds varied from about 1.3 dB (for wideband, interaurally correlated noise) to about 3 dB (for narrow noise centered at 500 Hz, interaurally uncorrelated). The results will be discussed in terms of the tradability of bandwidth, duration, and interaurally redundant information available in noisy stimuli. [Supported by NSF.]
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Lateralization and loudness of high‐frequency tones under masking (A)

Mark E. Perkins and M. Pavel

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S87-S87 (1982); (1 page)

Online Publication Date: 12 Aug 2005

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The apparent location of a 4000‐Hz tone presented to both ears will depend on the relative intensity of the signals. The position of the image can be affected by addition of noise in one of the ears; the apparent location will shift toward the ear without noise. This effect of noise on lateralization has some similarity to partial masking. We compared the effect of noise on lateralization and loudness by examining a property of the partial masking data called shift invariance [M. Pavel and G. J. Iverson, J. Acoust. Soc. Am. 69, 1126–1131 (1981)]. Using a transformed up‐down method in 2IFC paradigm, subjects adjusted the level of a masked tone in one channel in order to center the image of a tone in quiet presented in the other channel. As expected, these data exhibit “recruitment”‐like behavior familiar from studies of partial masking of loudness. The data suggest that shift invariance holds for the lateralization data and therefore provides a convenient means of relating the loudness matching and lateralization tasks.
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Model of a central lateralization processor—Quantitative evaluation (A)

Jens Blauert, Werner Lindemann, and Klaus Gruber

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S87-S87 (1982); (1 page)

Online Publication Date: 12 Aug 2005

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It is established that the hearing system interprets interaural arrival time differences as well as interaural level differences when forming the lateral position of auditory events. Models of binaural signal processing have been constructed which perform the evaluation of arrival time differences and level differences either by means of two separate stages of processing (time difference processor plus level difference processor) or by one single stage which can handle time differences as well as level differences. The present paper deals with a model of the latter kind which has previously been proposed by the first author [Proceedings of the 5th International Congress of Hearing, edited by v. d. Brink and Bilsen (Delft U. P., Delft, 1980), pp. 421–424]. Examples of a quantitative evaluation of the model with respect to psychoacoustical data on lateralization and lateralization blur will be reported. Further implications of the model will be discussed.
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A predictive model for binaural advantages in speech intelligibility (A)

P. M. Zurek

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S87-S87 (1982); (1 page)

Online Publication Date: 12 Aug 2005

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This paper presents a model of binaural advantages in speech intelligibility applicable to anechoic conditions in which speech is masked by a single noise source, with speech and noise sources both located in the horizontal plane. First, frequency‐ and azimuth‐dependent sound‐pressure transformations (from Shaw's summary of amplitude measurements and Woodworth's equation for phase) are applied to obtain third‐octave signal and noise spectra at each ear. Next (following Levitt and Rabiner), the effective S/N ratio in each band is increased by the masking‐level difference, which is approximated with an equation (from Colburn's model of binaural interaction) that describes MLD dependence on relevant stimulus parameters. Monaural and binaural performance are then predicted using Articulation Theory (Kryter). Predictions are in reasonable agreement with data from seventeen studies of the effects of source azimuth and listening mode (monaural or binaural) on intelligibility. The model provides a quantitative framework for analyzing binaural advantages and for assessing the practical benefits of binaural hearing. [Work supported by NIH.]
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Binaural horizontal plane localization: Spectral cues as a factor (A)

Alan D. Musicant and Robert A. Butler

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S87-S87 (1982); (1 page)

Online Publication Date: 12 Aug 2005

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Binaural localization performance with broadband noise or 4‐kHz high‐pass noise was investigated under two conditions. An unoccluded pinna condition was compared to performance in a pinna cavity occluded condition. The external meatus was open. Loudspeakers were placed at 15° intervals from 360° through 270° to 180° azimuth. Subjects were asked to identify the loudspeaker from which a sound originated. Results indicated profound disturbances when the pinna cavities were occluded. The occurrence of front‐back reversals increased to approximately 40% for all positions with a high‐pass noise stimulus. With a broadband noise, only sound sources in the front were transposed to the rear. Accuracy, defined in terms of either proportion correct or error score, decreased significantly (p < 0.01) when the pinna cavity was occluded. A paramount role for spectral cues in binaural directional hearing is postulated. [Work supported by NIH.]
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Sphere‐cylinder discrimination by human observers using broadband sonar pulses (A)

Douglas W. Martin and Whitlow W. L. Au

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S87-S87 (1982); (1 page)

Online Publication Date: 12 Aug 2005

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Human listeners were presented with target echoes and were asked to indicate which of two target classes, spheres or cylinders, generated the echoes on each trial. Sessions were conducted using either one or two targets from each class. Stimuli were obtained using broadband, ultrasonic, dolphinlike pulses, which were digitally recorded and presented to subjects at 1/50 of the original sample rate. Stimuli thus presented had center frequencies of approximately 2.4 kHz and durations of approximately 50 ms. Targets included spheres and cylinders of various sizes made of solid foam, solid aluminum, and hollow steel. After training, the average probability of correct discrimination with the foam targets varied between 85% and 96% depending on which targets were included in a session. Discrimination between the metal spheres and cylinders always exceeded 90% in both two‐ and four‐target sessions. For both foam and metal targets, subjects reported using two discrimination cues: a higher pitch associated with the cylinder echoes, and more low‐frequency reverberation in the sphere echoes. While the target strength of cylinders increases with frequency, and that of spheres does not, the targets could not be separated into classes based only on observing their spectra.
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The phase distribution of the pressure alongside a manikin's head and on the surface of a sphere of equivalent perimeter (A)

George F. Kuhn

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S87-S88 (1982); (2 pages)

Online Publication Date: 12 Aug 2005

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The pressure‐phase distribution for a frontally incident wave was measured at typcial hearing aid locations, alongside the head of KEMAR and behind its pinna at 0.5, 1.0, 2.0, 4.0, 5.0, 6.3, and 8.0 kHz. The measured phase data and the predictions of the phase on the surface of a rigid sphere of equivalent perimeter as the head are in reasonable agreement throughout, except at 6.3 and 8.0 kHz directly behind the pinna. Here, the measured results at the immediate rear of the pinna's helix have phase jumps of nearly 180°. These phase jumps result from the first higher order transverse acoustic mode, excited in the pinna. However, this mode decays rapidly, causing the phase jumps to disappear at a nominal distance of 5 mm behind the pinna. Also, the measured phase data reaffirms the earlier theoretical predictions [G. F. Kuhn and T. Munro, J. Acoust. Soc. Am. 65, S138 (1979)] of phase‐derived interaural time differences for normally hearing listeners and for aided listeners calculated on the basis of a spherical model of the head. [The help of Ed Burnett with the phase measurements is gratefully acknowledged. Work supported by NSF].
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Wave effects and pressure distribution in the ear canal near the tympanic membrane (A)

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

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S88-S88 (1982); (1 page) | Cited 2 times

Online Publication Date: 12 Aug 2005

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The complicated geometry of the human tympanic membrane and adjoining portion of ear canal can be expected to affect the flow of acoustic energy into the middle ear at frequencies greater than 10 kHz. To explore the implications of this geometry we have studied the acoustical behavior of a series of experimental cavities with shapes chosen to characterize the various acoustical factors that could be anticipated. The presence of the eardrum was simulated by the inclusion of a plastic or paper film of appropriate size and location. Preliminary experiments indicate that the penetration of the incident acoustic wave into the wedge‐shaped volume representing the final 10 mm of ear canal is strongly frequency‐dependent, and that between 10 and 20 kHz the apparent plane of reflection moves inward by approximately 6 mm. Measurements of sound pressure distribution in this region indicate that pressure variations greater than 15 dB can be expected across the human tympanic membrane at 15 kHz. Existing theoretical models will need to be modified if they are to be relevant above 10 kHz.
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Directionality of sound pressure transformation at the cat's pinna (A)

Dennis P. Phillips, Michael B. Calford, John D. Pettigrew, Lindsay M. Aitkin, and Malcolm N. Semple

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S88-S88 (1982); (1 page)

Online Publication Date: 12 Aug 2005

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In anesthetized cats, pinna directionality was examined using the amplitude of the round window‐recorded cochlear microphonic as a quantitative indicator of tympanic sound pressure level (SPL) associated with free field tonal stimuli in anechoic space. For high frequencies (above 3.5 kHz), there was a circumscribed optimal area for tympanic SPL in the frontal ipsilateral sound field, confirming that the pinna has an acoustical axis. The directionality of the pinna, determined from the solid angle enclosed by the 5‐dB optimal area, increased with tonal frequency. Few low frequencies, no circumscribed optimal areas could be discerned. Excision of the pinna abolished the circumscribed optimal area for tympanic SPL and revealed that the pinna may produce up to 30‐dB amplification of tonal stimuli delivered “on‐axis.” This selective directional amplification is compatible with the view [J. C. Middlebrooks and J. D. Pettigrew, J. Neurosci. 1, 107–120 (1981)] that apart from a role in sound localization, active pinna movements could be used by the cat for the scrutiny of sound sources of interest at the expense of others.
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