This study measured the ability of subjects to localize broadband sound sources that varied in both horizontal and vertical location. Brief (150 ms) sounds were presented a free field, reported apparent stimulus location by turning face source; head orientation was electromagnetically. Localization continuous also tested estimate errors motor act orienting with head. performance excellent for brief front subject. The smallest errors, averaged across subjects, about 2° 3.5° dimensions,...

The virtual auditory space technique was used to quantify the relative strengths of interaural time difference (ITD), level (ILD), and spectral cues in determining perceived lateral angle wideband, low-pass, high-pass noise bursts. Listeners reported apparent locations targets that were presented over headphones filtered with listeners' own directional transfer functions. stimuli manipulated by delaying or attenuating signal one ear (by up 600 micros 20 dB) altering at both ears. Listener...

By conventional spike count measures, auditory neurons in the cat's anterior ectosylvian sulcus cortical area are broadly tuned for location of a sound source. Nevertheless, an artificial neural network was trained to classify temporal patterns single according location. The 73 percent coded with more than twice chance level accuracy, and consistently carried information counts alone. In contrast that sharply location, these appear encode locations throughout 360° azimuth.

Human subjects localized brief 1/6-oct bandpassed noise bursts that were centered at 6, 8, 10, and 12 kHz. All testing was done under binaural conditions. The horizontal component of subjects’ responses accurate, comparable to for broadband localization, but the vertical front/back components exhibited systematic errors. Specifically, tended cluster within restricted ranges specific each center frequency. directional transfer functions external ears measured 360 locations. spectra sounds...

Although the auditory cortex plays a necessary role in sound localization, physiological investigations reveal inhomogeneous sampling of space that is difficult to reconcile with localization behavior under assumption local spatial coding. Most neurons respond maximally sounds located far left or right side, few tuned frontal midline. Paradoxically, psychophysical studies show optimal acuity across In this paper, we revisit problem three fields cat cortex. each field, confirm neural...

This study examined inter-subject differences in the transfer functions from free field to human ear canal, which are commonly know as head-related functions. The directional components of such referred here (DTFs). DTFs 45 subjects varied systematically among regard frequencies spectral features peaks and notches. Inter-subject were quantified between 3.7 12.9 kHz for sound-source directions throughout coordinate sphere. For each pair subjects, an optimal frequency scale factor aligned and,...

This study examined virtual sound localization in three conditions that differed according to the directional transfer functions (DTFs) were used synthesize targets. The own-ear and other-ear DTFs measured from listeners’ own ears those other subjects, respectively. scaled-ear condition employed scaled frequency minimize mismatch between spectral features listener’s subject’s DTFs. All measures of error typically lowest condition. In conditions, all tended increase proportion inter-subject...

Changes in sound pressures measured the ear canal are reported for broadband sources positioned at various locations about subject. These location-dependent one source of acoustical cues localization by human listeners. Sound were tested with horizontal and vertical resolution 10 degrees. levels miniature microphones placed inside two canals. Although amplitude spectra varied position microphone canal, it is shown that directional sensitivity any particular frequency stimulus independent...

Previous studies have demonstrated that the spike patterns of cortical neurons vary systematically as a function sound-source location such response single neuron can signal sound source throughout 360° azimuth. The present study examined specific features might transmit information related to location. Analysis was based on responses well-isolated units recorded from area A2 in α-chloralose-anesthetized cats. Stimuli were 80-ms noise bursts presented loudspeakers horizontal plane; azimuths...

This study examines patterns of auditory cortical activity elicited by single-pulse cochlear implant stimuli that vary in electrode configuration, place stimulation, and stimulus level. Recordings were made from the primary cortex (area A1) ketamine-anesthetized guinea pigs. The spatiotemporal pattern neural spike was measured simultaneously across 16 locations spanning approximately 2-3 octaves tonotopic axis. Such a pattern, averaged over 40 presentations any particular stimulus, defined...

We examined the coding of sound-source location by ensembles neurons in auditory cortex. Broadband noise bursts were presented from loudspeakers throughout 360 degrees horizontal plane. Sound levels varied 20 to 40 dB above neural thresholds. recorded temporal spike patterns simultaneously at 16 recording sites area A2 alpha-chloralose-anesthetized cats. Spike individual units counts and timing as a function location. Ensembles up 19 demonstrated additional sensitivity form relative among...

Middlebrooks, John C., Li Xu, Ann Clock Eddins, and David M. Green. Codes for sound-source location in nontonopic auditor cortex. J. Neurophysiol. 80: 863–881, 1998. We evaluated two hypothetical codes the auditory The topographical code assumed that single neurons are selective particular locations coded by cortical of small populations maximally activated neurons. distributed responses individual can carry information about throughout 360° azimuth accurate sound localization derives from...

Interaural envelope delays were measured in six human subjects as a function of the location movable sound source, bandpassed between 3 and 16 kHz. A total 324 source locations tested horizontal vertical increments 10°. method is described for estimating complex directional transfer external ear, independent position recording microphone ear canal. To compute interaural delays, functions from left right ears convolved with critical-band filter, envelopes computed, cross correlated. well...

This report explains the use of a complementary series, Golay codes, for probing impulse response external ear. The codes are used to measure both resonance human ear canal, using sealed sound-delivery system, and transfer function pinna, free-field source. With two series 512 binary numbers, improvement in signal-to-noise ratio over single approaches theoretical value 30.1 dB [10 log(2⋅512)]. technique has many same properties as maximal-length sequences [M. R. Schroeder, J. Acoust. Soc....

Deaf people who use cochlear implants show surprisingly poor sensitivity to the temporal fine structure of sounds. One possible reason is that conventional cannot activate selectively auditory-nerve fibers having low characteristic frequencies (CFs), which, in normal hearing, phase lock stimulus structure. Recently, we tested animals an alternative mode auditory prosthesis using penetrating electrodes permit frequency-specific excitation all frequency regions. We present here measures...

In a complex auditory scene, "cocktail party" for example, listeners can disentangle multiple competing sequences of sounds. A recent psychophysical study in our laboratory demonstrated robust spatial component stream segregation showing ∼8° acuity. Here, we recorded single- and multiple-neuron responses from the primary cortex anesthetized cats while presenting interleaved sound that human would experience as segregated streams. Sequences broadband sounds alternated between pairs locations....

We evaluated the spatial selectivity of auditory cortical neurons in awake cats. Single- and multiunit activity was recorded primary cortex as animals performed a nonspatial discrimination or sat idly. Their heads were unrestrained, head position tracked. Broadband sounds delivered from locations throughout 360 degrees on horizontal plane, source expressed head-centered coordinates. As anesthetized animals, firing rates most units modulated by sound location, responded best to contralateral...