Disparities in time and intensity are the two chief cues animals use for localizing a sound source in space. Echolocating bats belonging to the family Molossidae emit brief, ultrasonic signals for orientation that sweep downward about an octave over the duration of the pulse. Due to acoustic shadowing and the ...

In the present study derived auditory brain stem responses utilizing high pass masking were used to determine the frequency dependence of interear asymmetries and binaural interaction. Eight female adults with normal hearing participated in this study. The ABR was recorded for right and left ears and binaurally with clicks alone ...

The frequency specificity of the binaural interaction in brainstem auditory evoked potentials (BAEP) was investigated in ten normal-hearing young adults. A novel stimulus paradigm was devised to reduce the influence of the acoustic reflex (middle ear muscle contraction) on the BAEP, and to minimize the effect of variations in noise ...

This article describes a new model that predicts the subjective lateral position of bandpass stimuli. It is assumed, as in other models, that stimuli are bandpass filtered and rectified, and that the rectified outputs of filters with matching center frequencies undergo interaural cross correlation. The model specifies and utilizes the ...

Eight listeners were required to locate a train of 4.5-kHz high-pass noise bursts emanating from loudspeakers positioned +/- 30, +/- 20, +/- 10, and 0 deg re: interaural axis. The vertical array of loudspeakers was placed at 45, 90, and 135 deg left of midline. The various experimental conditions incorporated ...

The masking-level difference (MLD) for a 500-Hz monaural pure-tone signal was examined as a function of the interaural phase shift of a 100-Hz-wide noise band centered on 500 Hz. Results indicated that the MLD decreased in magnitude as the interaural phase shift of the masker increased. In a second experiment, ...

Discrimination of interaural differences of level (IDLs) was measured for pure tones as a function of frequency and as a function of the interaural difference of phase or level of a standard. Varying the interaural difference of the standard was assumed to change the lateral position of its intracranial image. ...

The acoustical properties of the external ear of the barn owl (Tyto alba) were studied by measuring sound pressure in the ear canal and outer ear cavity. Under normal conditions, pressure amplification by the external ear reaches about 20 dB between 3-9 kHz but decreases sharply above 10 kHz. The ...

A study was made of the effect of interaural time delay (ITD) and acoustic headshadow on binaural speech intelligibility in noise. A free-field condition was simulated by presenting recordings, made with a KEMAR manikin in an anechoic room, through earphones. Recordings were made of speech, reproduced in front of the ...

Detectability of binaurally presented 400- and 800-Hz tonal signals was investigated in an adaptive, two-interval forced-choice experiment. A continuous 3150-Hz low-pass noise masker was presented either diotically (No), interaurally uncorrelated (NU), or interaurally phase-reversed (N pi), at an overall level of 70 dB SPL. Signal duration was either 100 or ...

Dichotic stimulation with binaurally presented click trains at time-varying interaural differences of stimulation caused a pronounced sensation of fused image (FI) movement in man. Threshold click rate in the trains needed for the FI movement sensation during variations of interaural time differences of stimulation equalled 7.6 Hz and during variations ...

Previous investigations have shown that binaural hearing is often abnormal in patients having conductive hearing losses, and even in patients who have had hearing thresholds corrected by middle ear surgery. The present study assessed further the masking-level difference (MLD) in patients who had previously undergone middle ear surgery. The stimuli ...

Recently, we (Lauter & Loomis, 1986) reported variability measures of the latency of five vertex-positive auditory brainstem response (ABR) peaks collected under a repeated-measures experimental design. Seven subjects were tested, each on eight separate sessions, for brainstem auditory evoked response to monaural right, monaural left, and binaural stimulus presentation. This ...

The directional sensitivity of the outer ear of the guinea pig was determined by recording changes in the amplitude of the cochlear microphonic to frequencies between 1 and 20 kHz as the location of the sound source was changed throughout 360 degrees of horizontal auditory space. The directional responses to ...

1. We tested the coincidence, or cross-correlation, model of Jeffress, which proposes a neuronal mechanism for sensitivity to interaural time differences (ITDs) in low-frequency cells in the central nucleus of the inferior colliculus (ICC) of the cat. Different tokens of Gaussian noise stimuli were delivered to the two ears. We ...

1. We studied cells in the central nucleus of the inferior colliculus of the cat that were sensitive to interaural time delays (ITDs) in order to evaluate the influence of the stimulus spectrum of noise signals. Stimuli were sharply filtered low-, high-, and band-pass noise signals whose cutoff frequencies and ...

We studied the interaural phase sensitivity of 85 units in the inferior colliculus (IC) of the unanesthetized rabbit. We assessed this sensitivity at several frequencies within each unit's responsive range. The interaural phase disparity was varied by delivering tones that differed by 1 Hz to the two ears, resulting in ...

This study examines the influence of external ear position on the auditory spatial tuning of single units in the superior colliculus of the anesthetized cat. Unit responses to broad-band stimuli presented in a free sound field were measured with the external ears in a forward symmetrical position or with one ...

A study is reported in which it is shown that observers can use at least three types of acoustic variables that indicate reliably when a moving sound source is passing: interaural temporal differences, the Doppler effect, and amplitude change. Each of these variables was presented in isolation and each was ...

The changes in sound pressure level (SPL) at the two ears produced by azimuthal displacements of a free-field sound source in the interaural horizontal plane in frontal space were measured in anesthetized cats and the resultant interaural intensity differences (IIDs) were derived by subtraction. The mean curves at different frequencies ...

A series of three experiments used the method of magnitude estimation to examine binaural summation of the loudness of a 1000-Hz tone heard in the quiet and against various backgrounds of masking noise. In the quiet, binaural loudness as measured in sones, is twice monaural loudness. Two conditions of noise ...

The barn owl uses the interaural difference in the timing of sounds to determine the azimuth of the source. When the sound has a wide frequency band, localization is precise. When localizing tones, however, the barn owl errs in a manner that suggests that it is confused by phantom targets. ...

Tests were conducted to determine which horizontal reflection angles are most effective in stimulating subjective diffuseness for a listener in a room. Paired comparison tests were carried out where subjects were asked to judge in which of two sound fields they perceived more diffuseness. Results show that the most effective ...

A theory is presented that describes the binaural processing of interaural time or phase differences. It is an elaboration of the central spectrum concept for the explanation of dichotic pitch phenomena [F. A. Bilsen, "Pitch of noise signals: Evidence for a 'central spectrum'," J. Acoust. Soc. Am. 61, 150-161 (1977)]. ...

It is well known and universally accepted that people's ability to use ongoing interaural temporal disparities conveyed via pure tones is limited to frequencies below 1600 Hz. We wish to determine if this limitation is the result of the constant amplitude and periodic axis-crossings which characterize pure tones. To this ...

The relationship between interaural correlation discrimination and binaural detection was investigated using common experimental procedures and common subjects. Psychometric functions were obtained for four normal-hearing subjects at 500 and 4000 Hz using third-octave noise signals for the correlation discrimination experiment, and pure-tone signals and third-octave noise maskers for the detection ...

The broadening and splitting of auditory events in dichotic listening conditions with various degrees of interaural coherence are discussed. By using a psychoacoustical mapping method, it has been possible to observe broadening and splitting for a wide range of stimuli, including broadband pink noise as well as bandpass noises with ...

We examined the responses of low-frequency neurons in the central nucleus of the inferior colliculus (ICC) of the cat to interaurally delayed, wideband noise stimuli. The stimuli were pseudorandom noise signals that were generated digitally with a nominal bandwidth of 60-4,000 Hz. We also compared the responses to noise with ...

Three trained adults with normal hearing were exposed to a continuous 1-kc/s pure tone in both ears simultaneously at 100 db SPL. In the R ear the tone was attenuated at 1 db/sec until it was inaudible. In the L ear the tone was attenuated at 5 db/sec, and S ...

A study is reported in which the acuity of azimuth and elevation discrimination under monaural listening conditions was measured. Six subjects localised a sound source (white noise through a speaker) which varied in position over a range of elevations (-40 degrees to +40 degrees) and azimuths (0 degrees to 180 ...

Seven subjects were tested, each on eight separate sessions, for brainstem auditory evoked responses to monaural right, monaural left, and binaural stimulus presentations. Comparisons of between-subject vs. within-subject variability of the absolute latencies of vertex-positive peaks expressed in terms of the coefficient of variation indicate that: within-subject stability is greater ...

Listeners located, monaurally and binaurally, an 8.0 kHz centered noise burst whose bandwidth was set at 2.0, 4.0, 6.0 and 8.0 kHz. Loudspeakers, placed 7.5 degrees apart, covered an arc extending from 15 degrees to 165 degrees to the left of midline. Listeners reported the number of that loudspeaker from ...

This study of the neural representation of sound location in the bat Pteronotus parnellii describes how the peripheral and central components of its auditory system shape the horizontal and vertical spatial selectivity of single neurons in the inferior colliculus. Pteronotus extracts spatial information from the echoes of an emitted pulse ...

A series of experiments was performed to examine the extent to which precision of interaural time discrimination depends on the sound-pressure level (SPL) and/or sensation level (SL) of the signal. All experiments used a tone burst signal and a continuous white noise masker, which was either diotic or interaurally phase ...

Auditory localization was studied in a room bounded by a single acoustically reflective surface. The position of that surface was varied so as to stimulate a floor, a ceiling, and left and right side walls. The surface was eliminated in one condition so that we could examine localization in free ...

It has long been recognized that listeners are sensitive to interaural temporal disparities (ITDs) of low-frequency (i.e., below 1600 Hz) stimuli. Within the last three decades, it has often been demonstrated that listeners are also sensitive to ITDs within the envelope of high-frequency, complex stimuli. Because these studies, for the ...

Magnitude estimates (M.E.) of loudness of a 1-kc/s tone in the R ear at 60 db SPL were required over three 3-phase sessions from 15 normal-hearing young adults. The initial tone in the session was arbitrarily assigned a value of "60 units" in instructions to the S. The session was ...

Several recent investigations suggest that listeners either cannot or do not use envelope-based interaural temporal disparities (ITDs) to lateralize low-frequency sounds [G.B. Henning, J. Acoust. Soc. Am. 68, 446-453 (1980); G.B. Henning and J. Ashton, Hear. Res. 4, 185-194 (1981); G.B. Henning, Hear. Res. 9, 153-172 (1983)]. We believe listeners ...

Three experiments examined the effect of gaze shifts on overall performance and ear differences in dichotic listening. In the first two experiments, lights were switched on and off so as to induce rightward, leftward, or upward gaze during dichotic stimulation. The dichotic material consisted of musical passages in Experiment 1 ...

Most neurons in the deep and intermediate layers of the superior colliculus (SC) that respond to acoustic stimuli are sensitive to interaural intensity disparities (IIDs). We examine a model for the generation of sensitivity to IIDs that depends upon temporal coincidence of the inputs from each ear at a given ...

The topic of this paper concerns the judgement of just noticeable differences (JND) and of complete lateral position for dichotic 1 000-Hz stimuli with phase or onset time or delay differences and for a click. The 1 000-Hz sinusoids had 30 ms steady state with 10 or 50 ms rise/decay ...

Susceptance and conductance tympanograms were recorded from 10 normal subjects with probe frequencies ranging from 220 to 910 Hz. Tympanometric shapes progressed through an orderly sequence of patterns, becoming more complex with increasing probe frequency. When the direction of ear-canal air pressure change was from negative to positive values, more ...

The relation between binaural interaction type and spectro-temporal characteristics was studied for single units in the auditory midbrain of the grassfrog. Tonal and continuous wideband noise ensembles have been used as stimuli. Spectro-temporal sensitivities were determined for ipsi-, contra- and bilateral stimulus presentation by a closed sound system. Binaural interaction ...

The frequency dependence of the binaural interaction component of the auditory brainstem response was examined. Subjects included 24 with normal hearing and 5 with severe high-frequency losses. Tone pips of 100 and 80 dB pe SPL at 1 000 and 4 000 Hz were presented monaurally and binaurally. The binaural ...

Binaural interactions were recorded in auditory cortical (AI) neurons of anesthetized adult cats that had unilateral atresias created shortly after birth by surgically ligating and cutting one external ear canal. At the time of the recording experiment, the atresia and associated debris were removed and tones were delivered to both ...

Seven subjects located, monaurally and binaurally, narrow bands of noise originating in the horizontal plane. The stimuli were 1.0 kHz wide and centered at 4.0-14.0 kHz in steps of 0.5 kHz. The loudspeakers, 15 deg apart, were arranged in a semicircle (0-270-180 deg, azimuth). In the first part of the ...

A simple extension of the Webster-Jeffress model is presented together with its predictions for the effects of various stimulus parameters on the size of binaural masking-level differences (BMLDs). The four factors leading to BMLDs (just-noticeable differences (JNDs), temporal effects in simultaneous masking, binaural interaction, and temporal effects in non-simultaneous masking) ...

Several experiments are described in which subjects were required to discriminate differences in the spatial distribution of concurrently active sound sources in stereophonic arrays. For pure tone stimuli and binaural listening, systematic discrimination functions were observed when relatively small intersource frequency differences (approximately 30 Hz) were present. For tonal stimuli, ...

Recent psychoacoustic experiments have shown that interaural time differences provide adequate cues for lateralizing high-frequency sounds, provided the stimuli are complex and not pure tones. We present here physiological evidence in support of these findings. Neurons of high best frequency in the cat inferior colliculus respond to interaural phase differences ...

The basic principles essential for interpreting two-component, multiple frequency tympanograms first are reviewed. These principles then are applied to an analysis of tympanometric shape (conductance, susceptance, and admittance tympanograms) as a function of probe frequency in subjects with normal middle ear transmission systems. The final section presents tympanometric data from ...