Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Sound”

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 1,603 records · Page 89Linked to original sources
PubMedDate not supplied

[Sound sensations produced by electric stimulation of the structures of the middle ear and the tympanic chord].

Certain facts must be clearly understood before any attempt is made to analyse the sensations produced by electrical stimulation of the structures of the middle ear. Firstly, when the current passes from an electrode to the skin or to any polarised structure whatsoever, the point at which the electrode is applied and the skin behave like the two plates of a condenser microphone. Electrical vibrations are transformed into ordinary acoustic resonances which can travel through air or bone. These acoustic resonances are fairly pure in comparison with electrical vibrations, judged by the standards under investigation. If a continuous polarisation potential, which gives better distribution of the electrical charges, is added, the capacity of the microphone is increased and greater purity obtained. Consequently, the quality of sound heard in this way depends not only on the quality of this electro-physiological microphone but also on the quality of the internal ear. The acoustic effect produced in this way is called an electrophonic effect. Stevens, Jones and Flottorp described this. Therefore an internal ear which has lost the ability to hear high-pitched sound cannot hear them by means of this electrophonic effect any more than it can by ordinary auditory stimulation. Stimulation of the skin of the mastoid and of the external auditory meatus can be sensed by means of this electrophonic effect. Next, sensations recorded by means of direct stimulation of the acoustic nerve (DJOURNO and EYRIES) or by implantation of intra-cochlear electrodes (SIMMONS, DOYLE, MICHELSON) were studied. Sounds heard through stimulation of the structures of the middle ear should be analysed in the light of these findings and bearing in mind that very strong stimulation of the promontory or of the auditory meatus always causes an auditory sensation without frequency awareness due to global stimulation of the acoustic nerve (faciaestations appeared when experiments, the results of which are described, were carried out, although there is a possibility of episode vestibular irritation. These stimulations were in fact always very weak. Our results were analysed in relation to the quality of the internal ear: completely deaf, serious condition, internal ear normal. The impulses were provided by a direct current battery: these were square with a frequency of between 50 and 900 Hertz, a tension of 0 to 8 volts per 1/10 volt. The electrode was bipolar. The experiments were monitored from time to time by oscilloscope. Mention should be made of the technical and psychological precautions to be observed when stimulation of this kind is carried out if results of any value are to be obtained: a relaxed, sensible patient with whom one can communicate easily. Not much can be gathered from a person deaf in both ears. With the ear opened, the posterior part of the tympanum pulled forward, stimulation of the round window always results in production of a sound at a threshold of 0.5 to 2.5 volts.

Acoustic Stimulation↗
PubMedDate not supplied

[Analysis of intrauterine sounds and their tranquillizing effects on the newborn infant].

The authors have made a piezo-electric microphone in order to tap and analyse intrauterine sounds. The band that is used ranges from 3 - 700 Hz. A sound that has a small microphone at its tip is introduced into the uterus and then relayed to an amplifier. The sound mainly comes from the blood vessels and their frequency ranges between a few Hz and a thous and Hz. The acoustic pressure is big for low frequencies and weak for high frequencies. The sounds that are heard in the uterus have a calming effect on new-born children and stop them crying in 86% of cases where it has been tried. It sends them to sleep in 30% and this has been confirmed by E.E.G. This method is more effective than the older ones which used "slumber tone". The reason is that the product is the same as that which has been experienced by the fetus in utero.

Female↗
PubMed1994

[Relationship between power spectra of breath sounds and inspiratory flows at different frequencies].

Regional ventilation and changes in airway caliber have been studied by analysis of breath sounds. The aim of this study was to find which frequency band is most suitable for such purposes. The subjects were 19 healthy men. Breath sounds at 6 sites on the chest wall, airflow rate at the mouth, and ECG were digitized and recorded for 30 seconds. Power spectra of breath sounds at various frequency bands (10-50 Hz, 50-100 Hz, 100-150 Hz, ...., 950-1000 Hz) were calculated with a fast-Fourier transform (FFT) for every block of 512 points (102.4 msec), and mean airflow rates for the blocks were calculated. Data recorded during inspiration when airflow ranged between 0.5 L/s and 3 L/s were analyzed. For frequency bands from 150 Hz to 850 Hz the logarithms of the power spectra were linearly correlated with the logarithms of the airflow rates, and the correlation coefficients exceeded 0.8, but for lower frequency bands the correlations were poor. When the data contaminated by heart sounds and those recorded late in inspiration were excluded the correlations at frequency bands below 150 Hz improved. The slope of log (power)/log (flow) was about 4 for the bands from 100 to 300 Hz, but it became steeper (4 to 6) for higher frequency bands. This means that the power spectra were proportional to the fourth power of the airflow rate for bands below 300 Hz, but the relation was from the fourth to the sixth power for higher frequency bands.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Acoustic mechanisms in middle ear sound transfer.

This article reviews the mechanisms involved in the sound conduction process. This review includes both the physics of sound energy and the system of sound transmission through the middle ear. Several basic clinical defects of the middle ear are described as to their influence on sound conduction along with typical audiometric patterns associated with these defects.

Acoustics↗
PubMed1994

Acoustic and hearing aid circuit variables affecting the tolerability of aided impulsive-type sounds.

The tolerability of aided impulsive-type stimuli was investigated in a group of 13 hearing-impaired listeners. Two linear circuits (one with a class A and one with a class D output stage) and one adaptive frequency response (AFR) circuit (with a class D output stage) were investigated. In a three-way paired-comparison task, subjects chose the hearing aid that was most tolerable when 75 dB sound pressure level (SPL) impulsive-type sounds were presented. Real-ear measurements of rms SPL, peak SPL, crest factor, and spectral distribution were made to determine which of these variables was most closely associated with behavioral tolerability scores. Results indicated significant differences across hearing aids for tolerability scores, rms sound pressure levels, and spectral peak frequencies. Highest tolerability scores were associated with the hearing aid that produced the lowest rms sound pressure levels in the ear canal (class D AFR). Significant correlations were found between tolerability and both rms SPL and peak SPL. Results are discussed in terms of circuit algorithm and in terms of the possible effects of hearing aid saturation.

Audiometry↗
PubMed1994

Clinical comparison of temporomandibular joint sound auscultation and emission imaging studies.

Single photon-emission computerized tomography scintigraphy was used to examine 250 patients who previously had temporomandibular joint sounds auscultated and recorded with a Doppler machine. Patients were divided into four groups based on the presence of joint sounds: no sound, reciprocal clicks, reciprocal clicks with crepitus, and crepitus. Statistically significant differences between the groups and the single photon-emission computerized tomography scintigraphy results were determined. There was no correlation between these results and the no sound and crepitus groups, but significant correlation was established between positive results and crepitant joints with reciprocal clicks and noncrepitant clicking joints.

Analysis of Variance↗
PubMed1994

Sound evaluation of partially implantable piezoelectric middle ear implant: comparative study of frequency responses.

Two comparative studies were performed in six subjects using partially implantable middle ear implants (MEI). The sound quality was evaluated by speech discrimination tests and sound evaluation tests. In the first experiment, the performance of the output transducer of the MEI and an ear phone of a conventional hearing aid was compared. The MEI showed better results than the hearing aid in both the speech discrimination tests and sound quality rating. In the second experiment, four kinds of frequency responses for the external component of the MEI were compared. Sound quality evaluation in a wide frequency response with a peak at 4000 Hz were superior to those with the frequency response of the present MEI model. In conclusion, improvement of the external component in the frequency response can provide better performance of the MEI.

Audiometry↗
PubMed1993

Directional sensitivity of inferior collicular neurons of the big brown bat, Eptesicus fuscus, to sounds delivered from selected horizontal and vertical angles.

Under free field stimulation conditions, directional sensitivity of 336 inferior collicular (IC) neurons of 6 Eptesicus fuscus was studied by recording the minimum threshold (MT) and number of impulses of each neuron to a best frequency (BF) sound delivered from selected horizontal and vertical angles. An auditory response center was determined for each neuron by delivering a BF sound from a specific point of the bat's frontal auditory space. At the response center, the neuron had maximal directional sensitivity and lowest MT. Auditory response centers of all 336 IC neurons studied were located in the contralateral frontal auditory space and they shifted from lateral angles toward the midline with increasing BF. Sound direction affected the sharpness of frequency tuning (i.e. Q10-dB value) but not the BF and overall shape of the frequency threshold curve of a neuron. Sound direction also affected the MTs, number of impulses and intensity-rate functions but not the discharge patterns of IC neurons. High BF neurons generally had sharper directional sensitivity than low BF neurons. Bending downward the pinna contralateral to the recording site increased a neuron's MT and shifted its response center downward and toward the midline of the bat's frontal auditory space. The effect of pinna bending on a neuron's MT and impulse directional curves can be explained on the basis of variation of its auditory response area and its MT.

Acoustic Stimulation↗
PubMed1993

Parallel pathways mediating both sound localization and gaze control in the forebrain and midbrain of the barn owl.

The hypothesis that sound localization and gaze control are mediated in parallel in the midbrain and forebrain was tested in the barn owl. The midbrain pathway for gaze control was interrupted by reversible inactivation (muscimol injection) or lesion of the optic tectum. Auditory input to the forebrain was disrupted by reversible inactivation or lesion of the primary thalamic auditory nucleus, nucleus ovoidalis (homolog of the medial geniculate nucleus). Barn owls were trained to orient their gaze toward auditory or visual stimuli presented from random locations in a darkened sound chamber. Auditory and visual test stimuli were brief so that the stimulus was over before the orienting response was completed. The accuracy and kinetics of the orienting responses were measured with a search coil attached to the head. Unilateral inactivation of the optic tectum had immediate and long-lasting effects on auditory orienting behavior. The owls failed to respond on a high percentage of trials when the auditory test stimulus was located on the side contralateral to the inactivated tectum. When they did respond, the response was usually (but not always) short of the target, and the latency of the response was abnormally long. When the auditory stimulus was located on the side ipsilateral to the inactivated tectum, responses were reliable and accurate, and the latency of responses was shorter than normal. In a tectally lesioned animal, response probability and latency to contralateral sounds returned to normal within 2 weeks, but the increase in response error (due to undershooting) persisted for at least 12 weeks. Despite abnormalities in the response, all of the owls were capable of localizing and orienting to contralateral auditory stimuli on some trials with the optic tectum inactivated or lesioned. This was not true for contralateral visual stimuli. Immediately following tectal inactivation, the owls exhibited complete neglect for visual stimuli located more than 20 degrees to the contralateral side (i.e., beyond the edge of the visual field of the ipsilateral eye). In the tectally lesioned animal, this neglect diminished with time. Unilateral inactivation of nucleus ovoidalis had different effects in three owls. Response error to contralateral sound sources increased for one owl and decreased for two; response error to ipsilateral sources did not change significantly for any. The probability of response to ipsilateral (but not contralateral) stimuli decreased for one owl. The latency of response to ipsilateral (but not contralateral) stimuli increased for one and decreased for another. All of the owls, however, routinely localized and oriented toward ipsilateral and contralateral auditory stimuli with nucleus ovoidalis inactivated.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1993

Sound-localization deficits induced by lesions in the barn owl's auditory space map.

Barn owls possess a two-dimensional map of auditory space. The map appears in its final form in the external nucleus of the inferior colliculus (ICx) and is projected from there to the optic tectum (OT). To determine the role of the map in ICx or its projected version in OT in the localization of acoustic stimuli, head movements of three adult owls were recorded before and after lesioning parts of the map either in ICx or in OT. Small electrolytic lesions caused sound-localization deficits that were characterized by failures to turn, turns away from the sound source, increased response latencies, and reduced turning amplitudes. These deficits occurred at azimuths expected from the physiological data obtained at the lesion site before passing current. They extended over an azimuthal range of some 20 degrees. Thus, this is the first unambiguous demonstration, for sound localization, of a deficit covering a well circumscribed area within an auditory hemifield. Since the major lesion deficits were restricted to one hemifield, a second lesion was made in the space map of the other side of the brain in each animal. The second lesion resulted in behavioral deficits qualitatively similar to those produced by the first lesion. In total, the study is based on nine lesions, three in each owl. Two lesions were sham lesions. These and two further lesions did not produce a measurable deficit. In four of the five remaining cases, in which a behavioral deficit was observed initially, the behavioral performance recovered with time. In two cases, the deficit disappeared completely. Although improvement occurred also in the remaining two cases, prelesion response amplitudes were not reached in one case, and response latency did not reach prelesion values in the other case. Because the behavioral deficits induced by the second lesions disappeared in the same way as did the deficits induced by the first lesions, the possibility is excluded that the animals learned to respond tactically, that is, that they learned to associate "unlocatable sounds" with the lesioned side. The deficits were also not due to a generalized motor impairment, because immediately after the lesion the animals responded as they did before the lesion to stimulation from outside the well circumscribed affected region of space. The possibility is discussed that plasticity after small central (neural) injuries is maintained longer in the lifetime of an animal than plasticity after peripheral (mechanical) manipulations.

Animals↗
PubMed1993

Neural computations for sound pattern recognition: evidence for summation of an array of frequency filters in an echolocating bat.

Microchiropteran bats use an auditory sonar system for orientation and prey capture. Many bats use highly structured constant-frequency (CF) and frequency-modulated (FM) sonar orientation signals. Mechanisms for sound pattern recognition are important for the perception of these and other types of auditory signals. The processing and recognition of FM sound components appears to be important for certain complex perceptual tasks, including target distance perception. I have conducted behavioral studies using artificial echoes to simulate the conditions of a bat flying toward a target. An innate vocalization response of the bat to the simulated approaching target was used to assess the ability of the bat to analyze the structure of and extract distance information from different types of synthetic FM sound patterns. The bat's performance depended on the structure of the artificial echo. The pattern recognition performance of the bats was similar when they were presented with either a naturally structured artificial CF/FM echo or an artificial CF/FM echo containing an FM component consisting of a series of pure tone steps. The ability of the bats to recognize appropriately the structure of an FM signal constructed from a sequence of pure tones depended on the number of pure tone steps in the series. Noctilio was able to recognize FM sound patterns containing 99 or greater pure tone steps. The minimum required number of pure tone steps could be distributed over different frequency ranges. The bats were able to resolve individual tone steps in the series that were separated by at least 100 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Low frequency analysis of opening sound for detection of single leg separation of Björk-Shiley Convexo-Concave heart valves.

The aim of the study was to evaluate the potential of low frequency analysis of valve opening sounds in order to detect the presence of single leg separation of the outlet strut of Björk-Shiley convexo-concave (BSCC) valves. Single leg separation is believed to precede outlet strut fracture. Phonocardiograms (PCG) of 28 patients with BSCC mitral valves were recorded and filtered to limit the frequency bandwidth between 90 and 1400 Hz (-20 dB). Twenty-four patients had BSCC valves that were presumably unimpaired and four patients had BSCC valves with single leg separation. Spectral analysis consisted of computing the power spectrum for 30 opening sounds for each patient using a fast Fourier transform (FFT) algorithm on an IBM-PC compatible computer. For each patient, the power spectra of the selected opening sounds were averaged and normalized in amplitude on a 0-100% linear scale. A ratio of the high to the low frequency area of the averaged power spectra was computed and evaluated as a diagnostic feature to identify the valves with single leg separation. Six cut-off frequencies serving to distinguish between high and low frequency areas of the spectra were tested: 400, 450, 500, 550, 600, and 650 Hz. The results showed that the high-to-low frequency area ratios tested were all able to identify valves with single leg separation. The correct classification performance was 96.4%. The sensitivity to detect valves with single leg separation was 75% and the specificity was 100%. The positive predictive value was 100% and the negative predictive value 96%. The study confirmed the potential of low frequency analysis of valve opening sounds to detect single leg separation of the outlet strut of BSCC valves implanted in humans.

Algorithms↗
PubMed1996

Tolerance to sound intensity of binaural coincidence detection in the nucleus laminaris of the owl.

Neurons of the owl's nucleus laminaris serve as coincidence detectors for measurement of interaural time difference. The discharge rate of nucleus laminaris neurons for both monaural and binaural stimulation increased with sound intensity until they reached an asymptote. Intense sounds affected neither the ratio between binaural and monaural responses nor the interaural time difference for which nucleus laminaris neurons were selective. Theoretical analysis showed that high afferent discharge rates cause coincidence detectors with only excitatory input to lose their selectivity for interaural time difference when coincidence of impulses from the same side becomes as likely as that of impulses from the two sides. We hypothesize that inhibitory input whose strength increases with sound intensity protects nucleus laminaris neurons from losing their sensitivity to interaural time difference with intense sounds.

Acoustic Stimulation↗
PubMed1998

Sound localization in the median sagittal plane by listeners with presbyacusis.

In Experiment 1, a group of listeners with substantial hearing loss due to presbyacusis and a group of listeners with normal hearing were given three localization tests: a frontal plane test in which they judged whether sounds came from the left, overhead, or the right; a sagittal plane test in which they judged whether sounds came from directly in front, overhead, or behind; and an elevation test in which they judged the vertical position of sounds coming from in front. The two groups performed similarly on the frontal plane test, which chiefly depended upon their ability to use binaural localization cues. They performed differently on the sagittal plane and elevation tests, for which the predominant localization cues were spectral. The listeners with presbyacusis were substantially less accurate than those with normal hearing in both of these instances. They had particular difficulty judging source elevation, rarely scoring much above chance. Follow-up testing of a group of subjects in the early stages of presbyacusis showed localization performance that was intermediate to the other two groups, but far more like that of the normal-hearing listeners. In Experiment 2, additional tests were run with the following conditions designed to encourage improved performance by listeners with presbyacusic hearing loss: (1) filtering of stimuli to preclude masking of more informative high-frequency components by low frequencies; (2) simplification of the elevation test and greater spatial separation of its loudspeaker sources; and (3) use of hearing aids. Conditions 1 and 2 had no appreciable effect on performance; condition 3 significantly improved presbyacusic listeners' ability to localize in the sagittal plane, particularly when sounds came from the front.

Adult↗
PubMed2006

Differential representation of speech sounds in the human cerebral hemispheres.

Various methods in auditory neuroscience have been used to gain knowledge about the structure and function of the human auditory cortical system. Regardless of method, hemispheric differences are evident in the normal processing of speech sounds. This review article, augmented by the authors' own work, provides evidence that asymmetries exist in both cortical and subcortical structures of the human auditory system. Asymmetries are affected by stimulus type, for example, hemispheric activation patterns have been shown to change from right to left cortex as stimuli change from speech to nonspeech. In addition, the presence of noise has differential effects on the contribution of the two hemispheres. Modifications of typical asymmetric cortical patterns occur when pathology is present, as in hearing loss or tinnitus. We show that in response to speech sounds, individuals with unilateral hearing loss lose the normal asymmetric pattern due to both a decrease in contralateral hemispheric activity and an increase in the ipsilateral hemisphere. These studies demonstrate the utility of modern neuroimaging techniques in functional investigations of the human auditory system. Neuroimaging techniques may provide additional insight as to how the cortical auditory pathways change with experience, including sound deprivation (e.g., hearing loss) and sound experience (e.g., training). Such investigations may explain why some populations appear to be more vulnerable to changes in hemispheric symmetry such as children with learning problems and the elderly.

Acoustic Stimulation↗
PubMed1995

Sound stimulation induces Fos-related antigens in cells with common morphological properties throughout the auditory brainstem.

Cells within the auditory brainstem of cat that respond to sound by producing the transcription factor Fos or related proteins were identified by immunostaining with antisera against Fos and Zif/268. Within the cochlear nucleus, all antisera showed similar staining patterns, however, in the superior olive and inferior colliculus, staining patterns differed between antisera. Immunostained cells were characterized by their size, location, by the presence of perisomatic terminals that immunostained for glutamate decarboxylase or synaptophysin, or by electron microscopy. Most cell classes were not immunopositive. In the ventral cochlear nucleus, roughly 99% of Fos-positive cells had few perisomatic terminals. Within the superior olivary complex (SOC), the majority of immunopositive cells had few perisomatic terminals. Lateral olivocochlear cells were identified as Fos positive by their size, location, lack of perisomatic terminals, and positive costaining for acetylcholinesterase as evidenced by a novel reaction product. This report appears to be the first demonstration of these cells responding to sound stimulation. Within the inferior colliculus, bands of positive cells produced by tonal stimulation extended from the central nucleus throughout the dorsal cortex and the posterior pericentral region, a finding unexpected on the basis of previous electrophysiological recordings and anatomical studies of ascending inputs to the colliculus. Approximately 35% of Fos-positive cells in the inferior colliculus had plentiful perisomatic terminals. Results demonstrate a high degree of specificity of auditory cell types that respond to sound by producing Fos-like proteins and show that previously intractable physiological questions can be addressed by assaying for sound-induced production of these antigens.

Acoustic Stimulation↗
PubMed1984

Ontogenesis of learning: III. Variation in the rat's differential reflexive and learned responses to sound frequencies.

The ontogenesis of the rat's differential response to variation in sound frequency was investigated. Two behavioral procedures were employed: (a) a differential Pavlovian conditioning procedure that provided a means of inferring the pup's capacity to learn to respond differentially on the basis of sound frequency (e.g., 2000 Hz vs 900 Hz), and (b) a habituation-generalization task that indexed the capacity to discriminate different sound frequencies from the pup's reflexive behavior. Pups less than 17 days old failed to learn to respond differentially to a 2000-Hz vs 900-Hz tone (Experiment I, IIA, IIB, and III). In contrast, pups only 14 days old discriminated tones that differed by as little as 200 Hz when the reflex-habituation-generalization procedure was employed (Experiment IV). This suggests that the reflexive and learned behaviors, potentially controlled by sound frequency, are dissociated during ontogenesis, the former emerging prior to the latter. These data were interpreted within a neurobiological framework that related ontogenetic changes in behavioral capacity to a caudal-to-rostral maturational sequence in the ascending auditory system of the components that contribute to these capacities.

Acoustic Stimulation↗
PubMed1994

The effect of an intensive care unit sound environment on the development of habituation in healthy avian neonates.

There is increasing concern that environmental stimuli in the Neonatal Intensive Care Unit (NICU) may be detrimental to the preterm infants hospitalized there. Separately, there is longstanding recognition that preterm infants at 40 weeks postconceptional age habituate less reliably than full-term infants. This study uses a relevant animal model to test whether exposure to NICU sounds, as a single departure from normal neonatal experience, can alter habituation. Chicks were incubated, hatched, and reared in either a quiet or a NICU-sound environment. Habituation was measured by the length of time that chicks delay their ongoing peeping upon hearing a white noise stimulus. NICU-sound-reared 4-day-olds failed to habituate, showing as much responsiveness at the end of repeated stimulation as at the beginning. This is, to our knowledge, the first demonstration that atypical sound exposure alone can alter this fundamental aspect of neurosensory competence in an otherwise healty neonate.

Aging↗