Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Sound Localization”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18Linked to original sources
PubMed1990

[Directional hearing in relation to individual circadian biorhythm].

Acuity angle of the directional hearing was investigated in connection with the individual circadian rhythm. Two groups of 15 persons represented the morning and evening form of the circadian rhythm. Body temperature fixed the rhythm character. The evaluations of the angle acuity of the directional hearing were performed in the highest and the lowest point of body temperature as well as in the neutral point, which was determined in the morning group in the middle between the two extremes. The possibility of the sound localization in individual and linked with the body temperature circadian rhythm.

Acoustic Stimulation↗
PubMed1986

An acoustic approach to diver navigation.

Three experiments were carried out to assess the capability of divers to localize acoustic signals underwater and to navigate by them. In the first experiment, divers attempted to determine the correct distance to several underwater transducers projecting acoustic stimuli on a horizontal plane. The second experiment consisted of two related studies where the diver/subjects attempted to discover which of many possible stimuli would produce the most robust perception of underwater "sound movement," or the Underwater Auditory Phi Phenomenon (UAPP). A third experiment consisted of navigational swims by divers; the acoustic stimuli utilized were based on those identified in prior experiments as the most preferred. The results demonstrated that divers are able to discriminate among signals emanating from acoustic sources at various distances underwater and to do so at levels well above chance. Second, divers judged 500-Hz square waves to be the signal which best facilitated an acceptable UAPP; thermal noise and 1-kHz square waves followed in that order. However, these differences were only slight and, in practice, divers maintained that the noise signal was the most useful. Third, it was found that divers apparently can effectively navigate by means of auditory signals alone--at least within certain limits. Finally, a significant decrease in the discrimination abilities of divers for frequencies above 6 kHz suggests that intensity cues may not be as robust as time-of-arrival information with respect to underwater sound localization.

Acoustic Stimulation↗
PubMed1990

Directional dependence of interaural envelope delays.

Interaural envelope delays were measured in six human subjects as a function of the location of a movable sound source, bandpassed between 3 and 16 kHz. A total of 324 source locations were tested in horizontal and vertical increments of 10 degrees. A method is described for estimating the complex directional transfer function of the external ear, independent of the position of the recording microphone in the ear canal. To compute interaural envelope delays, directional transfer functions from the left and right ears were convolved with a critical-band filter, the envelopes were computed, and the envelopes were cross correlated. Interaural envelope delays, as well as interaural group delays, varied somewhat with the center frequency of the critical-band filter and with the vertical location of the sound source. Nevertheless, to a first approximation, envelope delays measured in the ear canals increased monotonically with increasing angle of incidence relative to the median plane, as they would for two microphones on the surface of a rigid sphere. The results are discussed in relation to the possible contribution of interaural envelope delays to sound localization behavior.

Attention↗
PubMed1992

Neural derivation of sound source location: resolution of spatial ambiguities in binaural cues.

Cues for sound localization are inherently spatially ambiguous. Nevertheless, most neurons in the barn owl's optic tectum (superior colliculus) have receptive fields for broadband noise stimuli that are restricted to a single region of space. This study characterizes the spatial ambiguities associated with two important sets of localization cues, interaural level differences (ILDs) and interaural phase differences (IPDs), and describes how information is integrated within and across frequencies to resolve these ambiguities. The auditory receptive fields of neurons in the optic tectum were measured with free-field sounds presented from a movable loudspeaker. In contrast to the single regions typical for broadband receptive fields, receptive fields for tonal stimuli usually included additional discrete regions of space (accessory fields). Based on acoustic measurements of ILD and IPD cues made in the external ear canals, it was shown that accessory fields corresponded to locations from which sound sources produced ILD and IPD values that were approximately the same as those arising from the broadband receptive field. In addition, accessory fields had inhibitory surrounds, corresponding to locations from which sound sources produced substantially different combinations of ILD and IPD values. Where an accessory field for one frequency overlapped with the inhibitory surround of a second frequency, an excitatory response to the first frequency could be reduced or eliminated by addition of the second frequency. Because tonal receptive fields for different frequencies always overlapped in the region of the broadband receptive field but tended not to overlap elsewhere, this integration of excitation and inhibition can account for the restriction of broadband receptive fields to a single region of space.

Animals↗
PubMed1994

Adaptive plasticity of the auditory space map in the optic tectum of adult and baby barn owls in response to external ear modification.

1. This study demonstrates the influence of experience on the establishment and maintenance of the auditory map of space in the optic tectum of the barn owl. Auditory experience was altered either by preventing the structures of the external ears (the facial ruff and preaural flaps) from appearing in baby barn owls (baby ruff-cut owls) or by removing these structures in adults (adult ruff-cut owls). These structures shape the binaural cues used for localizing sounds in both the horizontal and vertical dimensions. 2. The acoustic effects of removing the external ear structures were measured using probe tube microphones placed in the ear canals. In both baby and adult ruff-cut owls, the spatial pattern of binaural localization cues was dramatically different from normal: interaural level difference (ILD) changed with azimuth instead of with elevation, the rate of change of ILD across space was decreased relative to normal, and the rate of change of interaural time difference (ITD) across frontal space was increased relative to normal. 3. The neurophysiological representations of ITD and ILD in the optic tectum were measured before and > or = 3 mo after ruff removal in adults and beginning at 4.5 months of age in baby ruff-cut owls. Multiunit tuning to ITD and to ILD was measured using dichotic stimulation in ketamine-anesthetized owls. The tectal maps of ITD and ILD were reconstructed using visual receptive field location as a marker for recording site location in the optic tectum. 4. Adjustment of the tectal map of ITD to the altered spatial pattern of acoustic ITD was essentially complete in adults as well as in baby ruff-cut owls. This adjustment changed the magnification of ITD across the tectum, with resultant changes in ITD tuning at individual tectal sites of up to approximately 25 microseconds (approximately 5% of the physiological range) relative to normal values. 5. Adaptation of the tectal ILD map to the ruff-cut spatial pattern of acoustic ILD was substantial but clearly incomplete in both adult and baby ruff-cut owls. Although changes of up to approximately 15 dB (approximately 47% of the physiological range) relative to normal tuning were observed at certain tectal sites, the topography of the ILD map was always intermediate between normal and that predicted by the ruff-cut spatial pattern of acoustic ILD.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1984

Binaural interactions of single neurons in posterior field of cat auditory cortex.

In the auditory cortex of barbiturate-anesthetized cats, the posterior auditory field (area P) was identified by its tonotopic organization, and single neurons in that field were studied quantitatively with regard to their binaural interactions at their respective best frequencies, using calibrated, sealed stimulating systems. Almost 60% of the neurons studied displayed " summative " binaural interactions in that their responses to binaural, equally intense stimulation of the two ears were stronger than were their responses to monaural stimuli of the same intensity. For these neurons, latent periods were shorter for binaural stimuli than for monaural stimuli. Some field P neurons were sensitive to interaural intensity disparities and manifested that sensitivity in one of two forms. Cells that were excited by stimulation of one ear and inhibited by stimulation of the other typically displayed a sigmoidal relation of spike count to intensive disparity, with spike counts being larger when the disparity favored the contralateral ear. Cells that were unresponsive to monaural stimuli but responded securely to binaural stimuli usually displayed a peaked, nonmonotonic relation of spike count to interaural intensity disparity, with maximal responses being elicited by stimuli with zero or near-zero disparity. Some neurons of low best frequency were sensitive to variations in interaural phase delay. In all cases, this sensitivity was manifested as a cyclical relation of spike count to interaural delay, with the period of the cycle being that of the stimulating tone. The fact that the binaural interactions of field P neurons were similar to those of cells in the primary auditory cortex suggests that the previously described heightened spectral-amplitude selectivity of field P neurons has been achieved without cost to their sensitivity to a variety of parameters of binaural stimulation. The particular sensitivity of cortical neurons to variations in interaural disparities associated with midline or near-midline azimuths might constitute a neural mechanism for the behavioral finding that animals and humans show their greatest acuity in sound localization for stimulus locations in or near the midsagittal plane.

Animals↗
PubMed1991

Auditory cortex: comparative aspects of maps and plasticity.

Much recent work in the field of auditory cortex analysis consists of an intensified search for complex sound representation and sound localization mechanisms using tonotopic maps as a frame of reference. Mammalian species rely on parallel processing in multiple tonotopic and non-tonotopic maps but show different degrees of unit complexity, and orderly representation of acoustic dimensions in such maps depending on the predictability of sounds in their environment. Birds appear to rely chiefly on one tonotopic map which harbours multidimensional complex representations. During development and after partial hearing loss, tonotopic organization changes in a predictable manner. Learning also modifies the spatial representation of sounds and even modifies tonotopic organization, but the spatial rules involved in this process have not yet emerged.

Animals↗
PubMed1990

Direction-dependent spectral properties of cat external ear: new data and cross-species comparisons.

Free-field to eardrum transfer functions were measured in anesthetized cats inside an anechoic chamber. Direction-dependent transformations were determined by measurement of sound-pressure levels using a small probe tube microphone surgically implanted in a ventral position near the tympanic membrane. Loudspeaker and probe microphone characteristics were eliminated by subtraction of the signal recorded in the free field with no animal present. Complexities of the transfer function, which include the presence of prominent spectral notches in the 8- to 18-kHz frequency region, are due primarily to the acoustical properties of the pinna. Differential amplification of frequency components within the broadband stimulus occurs as a function of source direction. Spectral features vary systematically with changes in both elevation (EL) and azimuth (AZ). The contrast between a notch and its shoulders is enhanced in the interaural spectral records. Spectral data from single source locations and spatial data for single frequencies at many locations are presented and comparisons with other species are drawn. It is suggested that spectral features in the 8- to 18-kHz region provide some of the necessary spectral information for sound localization and that the contrast in spectral energy between the frequencies at the notch and its shoulders is a potential directional cue.

Acoustic Stimulation↗
PubMedDate not supplied

Neural plasticity in processing of sound location by the early blind: an event-related potential study.

Event-related potentials (ERPs) to a change in the locus of origin of a repetitive sound were studied in early blind human subjects. It was found that the N2b component of the ERP was posteriorly distributed on the scalp to that in the sighted control subjects. This suggests that the blind might use, to a larger extent than the sighted, parietal, or perhaps even occipital, brain areas in sound localization. The present results thus appear to demonstrate plastic changes in neural populations involved in processing of auditory space following early loss of vision.

Acoustic Stimulation↗
PubMed1994

Hearing in prairie dogs: transition between surface and subterranean rodents.

Behavioral audiograms were determined for four black-tailed and one white-tailed prairie dogs (Cynomys ludovicianus and C. leucurus) using a conditioned avoidance procedure. The hearing of black-tailed prairie dogs ranges from 29 Hz to 26 kHz and that of the white-tailed prairie dog from 44 Hz to 26 kHz (at sound pressure levels of 60 dB). Both species have good low-frequency hearing, especially black-tailed prairie dogs which can hear as low as 4 Hz and are more sensitive than any other rodent yet tested at frequencies below 63 Hz. In contrast, prairie dogs are relatively insensitive in their midrange and have poor high-frequency hearing. It is suggested that the reduced midrange sensitivity and high-frequency hearing are related to their adaptation to an underground lifestyle with its reduced selective pressure for sound localization. In this respect they appear to be intermediate between the more exclusively subterranean rodents (such as gophers and mole rats) and surface dwellers (such as chinchillas and kangaroo rats).

Acoustic Stimulation↗
PubMed1986

Auditory performance of children with unilateral sensorineural hearing loss.

Horizontal sound localization and syllable recognition skills were examined in a group of children with unilateral sensorineural hearing loss and a matched group of normal hearers. The results showed that the unilaterally hearing-impaired children performed more poorly than the normal counterparts in both localization and speech recognition of nonsense syllables. The unilaterally hearing-impaired children had considerable difficulty understanding in a background of noise. The clinical implications of these findings are discussed.

Achievement↗
PubMed1997

Audiogram of the big brown bat (Eptesicus fuscus).

The audiograms of three big brown bats (Eptesicus fuscus) were determined using a conditioned avoidance procedure. The average audiogram ranged from 0.850 kHz at 106 dB to 120 kHz at 83 dB SPL, with a best threshold of 7 dB at 20 kHz and a distinct decrease in sensitivity at 45 kHz. The results confirm those of a previous study by Dalland (1965a) that the big brown bat has good high-frequency hearing coupled with poor low-frequency hearing. Comparative analysis suggests that the bat's good high-frequency hearing initially evolved for passive sound localization and that it was later coopted for use in echolocation. In addition, the restricted low-frequency hearing of the big brown bat is typical of mammals with good high-frequency hearing.

Acoustic Stimulation↗
PubMed1992

Changing-loudness aftereffect following simulated movement: implications for channel hypotheses concerning sound level change and movement.

Listening to a tone changing unidirectionally in sound level causes an illusion of changing loudness in a steady tone afterward. This aftereffect may indicate channels for detecting the feature of change in sound level, which would primarily concern dynamic sound localization. Three subjects, one of whom was the author, participated in this study. The author predicted that opposite adaptation of the ears (the adapting stimulus is heard to move from one ear to the other) should lead to a movement aftereffect. This was not reported by the subjects. However, the subjects did report a changing-loudness aftereffect in a monaural test stimulus, and the characteristics of the changing-loudness aftereffect (such as its magnitude) were consistent with previous data, suggesting a two-stage channel hypothesis: Output from channels for several features, including sound-level change, simultaneously stimulate movement channels.

Attention↗
PubMed1990

Separating signal and noise in vibrotactile devices for the deaf.

This paper briefly reviews a series of experiments demonstrating that a sound-to-touch transform of signal and noise may be perceptually separated by providing tactile cues for sound localization. Following this, three experiments are reported in which it is shown that such stereotactile cues are available if two vibrotactile devices (Minifonators, produced by Siemens Co. Ltd.), are used instead of one. With this system, subjects were able to attend to a target signal (male voice) in white noise and when a female voice was presented simultaneously. This ability depended upon a sufficient spatial separation of the target and noise in acoustic space. These findings appear to have applications in the design of tactile hearing aids and cochlear implants when used in noisy environments or when more than one sound is present.

Adult↗
PubMed1995

Binaural noise stimulation of auditory callosal fibers of the cat: responses to interaural time delays.

The corpus callosum, the principal neocortical commissure, allows for the interhemispheric transfer of lateralized information between the hemispheres. The aim of the present experiment was to study callosal transfer of auditory information in the cat, with particular reference to its contribution to sound localization. The corpus callosum was approached under direct visual control, and axonic responses were recorded under light anesthesia using glass micro-pipettes. Results showed that auditory information is transmitted in the posterior portion of the callosum. Diotic presentations, in which interaural time delay was manipulated, indicated that, for a large number of fibers, the largest excitatory or inhibitory interactions were obtained at null interaural time delay, a condition which supports the notion of a callosal contribution to auditory midline fusion. However, an important number of callosal fibers was also found to be excited maximally at specific, non-zero interaural time delays, suggesting that they preferred sounds situated at spatial locations other than the midline. The results are discussed in relation to those obtained electrophysiologically for the visual and somesthesic modalities and in terms of results obtained in human and animal behavioral experiments.

Acoustic Stimulation↗
PubMed1986

Directional responses to sounds in young gerbils (Meriones unguiculatus).

Three experiments were conducted to determine the ability of infant gerbils to approach an auditory stimulus. In the first experiment, gerbil pups, 16-23 days of age, were tested in a circular apparatus with a central start area and a movable sound source located at one of eight positions around the perimeter. Stimuli included high- and low-intensity presentations of a tape-recorded gerbil social call, a broad-band white noise stimulus, and a no-stimulus control condition. The subjects showed a strong tendency to approach the low-intensity social call and a less pronounced tendency to approach the white noise. In the second experiment, gerbil pups were tested in the same apparatus with or without ear blocks to determine the role of binaural cues in directional approach responding. The tendency to approach a low-intensity vocalization was disrupted by obstruction of one ear but not by blocking both ears. Thus, binaural balance was shown to be important for early sound localization. In the third experiment, the tendency to approach a social call was compared at different ages, 12-15, 16-19, 20-23, and 24-27 days after birth. Approach responses were first seen at 16-19 days. The responses continued during the 20-23-day period but began to wane at 24-27 days of age.

Animals↗
PubMed1987

Auditory science tutorial. III: The role of the ascending pathways.

This paper attempts a thumbnail sketch of what is currently known about processing in the early parts of the auditory pathway. The paper briefly reviews the morphology and physiology of the auditory nuclei up to the inferior colliculi of the midbrain and discusses their function in processing sound information. Particular attention is paid to the role of these nuclei in sound localization and in analysing complex signals such as speech. One aim of the tutorial is to dispel any ideas that the peripheral auditory pathways are mere relays to the thalamus and cortex and to emphasize their fundamentally important role in auditory processing. The review is not comprehensive (indeed it can only touch upon some aspects of auditory processing) but key references are provided for those with more than just a passing interest.

Animals↗
PubMed1989

Neural coding of relational invariance in speech: human language analogs to the barn owl.

The ability to form perceptual equivalence classes from variable input stimuli is common in both animals and humans. Neural circuitry that can disambiguate ambiguous stimuli to arrive at perceptual constancy has been documented in the barn owl's inferior colliculus where sound-source azimuth is signaled by interaural phase differences spanning the frequency spectrum of the sound wave. Extrapolating from the sound-localization system of the barn owl to human speech, 2 hypothetical models are offered to conceptualize the neural realization of relative invariance in (a) categorization of stop consonants/b, d, g/ across varying vowel contexts and (b) vowel identity across speakers. 2 computational algorithms employing real speech data were used to establish acoustic commonalities to form neural mappings representing phonemic equivalence classes in the form of functional arrays similar to those seen in the barn owl.

Adult↗