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At least 1,405 records · Page 78Linked to original sources
PubMed2006

Cortical auditory systems: speech and other complex sounds.

The neural systems that mediate human perception of speech and other complex sounds are currently the focus of considerable research. Brain mapping studies have provided new insights into the cortical processing of complex sounds. Findings from three lines of brain mapping research--stroke-lesion, neuroimaging, and electrocortical mapping studies--are reviewed. Unresolved questions regarding the relative contributions of cortical and subcortical auditory processing and the existence of separate, functionally specialized, cortical auditory systems for processing speech and nonspeech sounds are discussed. An integrated approach is proposed for future research on the neural bases of complex sound processing.

Acoustics↗
PubMed1977

Sound levels for neonates in transit.

Sound levels were measured in a neonatal intensive care nursery as well as during transport in ambulance, rotary wing, and fixed wing aircrafts. In the nursery, under usual conditions, the sound levels were between 58 and 70 dB; while in transit, they were invariably higher, particularly in rotary wing aircarft ( greater than 90 dB). The observations suggest that neonates in transit are exposed to potentially hazardous sound levels. Provision of means to attenuate the sound is desirable as a part of stabilization of infant during transport.

Aircraft↗
PubMed1998

Role of acoustic striae in hearing: reflexive responses to elevated sound-sources.

This report is the fourth in a series describing the results of ablation-behavior experiments directed to the ascending output of the cochlear nuclei as it is conducted centrally within the acoustic striae. This fourth report focuses on the unique physiology of the fusiform or 'output' cells of the dorsal cochlear nucleus whose axons course through the dorsal acoustic stria (DAS). Because electrophysiological studies have shown that the cues for sensing the elevation of a sound source would seem to be best analyzed by the dorsal cochlear nucleus and projected centrally via its DAS, we tested normal cats and cats deprived of DAS for their ability to orient to elevated sources of broad-band noise. For behavioral testing, we made use of reflexive or unconditioned orienting responses to elevated sound sources using a similar method to one we have used previously for azimuth testing (Thompson GC, Masterton RB. Brainstem auditory pathways involved in reflexive head orientation to sound. J Neurophysiol 1978;41:1183-1202). The results show that cats deprived of their DAS do indeed have a marked deficit in their ability to orient to an elevated sound source. Further behavioral testing indicated that this deficit is not the secondary result of an attentional or peripheral motor deficit. Although the present results do not prove that the reflexive deficit is strictly auditory in nature, the deficit is notable in that it is the only one yet known to result from a lesion of the dorsal cochlear nucleus or its central projections.

Acoustic Stimulation↗
PubMed1997

The assessment of nasality with a nasometer and sound spectrography in patients with nasal polyposis.

With the development of computerized acoustic analysis systems, an objective measure of nasal speech has become readily available by means of a simple, noninvasive technique. In this study, we assessed the nasality in patients with multiple nasal polyposis before and after endoscopic sinus surgery. With the nasometer, we measured nasalance, which reflects the ratio of acoustic energy output of nasal sounds from the nasal and oral cavities, and the slope score of the nasogram curve. The nasalance scores of nasal sentences and the slope scores of the nasogram curves for all nasal consonants were significantly lower in patients with nasal polyposis than in healthy subjects. After surgery, however, the nasalance and slope scores increased significantly to the normal range. On the sound spectrographic analysis, the frequencies of the first nasal formant decreased slightly and the sound intensity increased slightly for all nasal consonants after surgery. However, no significant change was noticed in the frequencies of the second nasal formant. In conclusion, nasometric and sound spectrographic analyses are considered to be useful tools for objectively assessing the extent of nasality in patients with nasal airway obstruction.

Acoustics↗
PubMed1985

Temporomandibular joint sounds in patients with disc displacement.

Temporomandibular joint sounds have been viewed as signs of different pathological changes. However, the correlation between joint sounds on the one hand and function and morphology of the joint on the other, are not well documented. We have therefore presurgically recorded sound from 35 operated joints with disc displacement and have studied arthrographically and during surgery the position, function and configuration of the disc as well as arthrotic changes. 12 joints were silent, 12 elicited reciprocal clicking, 3 single clicking, and 8 crepitation. Joints with reciprocal clicking consistently showed disc displacement with reduction and silent and crepitating joints showed disc displacement without reduction. All joints with reciprocal clicking as well as most silent joints demonstrated non-arthrotic articular surfaces, whereas crepitation was recorded in both arthrotic and non-arthrotic joints. Our results implied that crepitation is a rather unreliable sign of arthrosis. Reciprocal clicking can be considered as an accurate sign of reduction of anteriorly displaced discs. However, neither the degree of displacement nor the degree of deformation of the disc could be disclosed by analysis of the sound. This information can only be obtained by further examination, such as arthrotomography.

Adolescent↗
PubMed2003

Relational discrimination learning between amplitude-modulated sounds in the rat.

We studied the cue used by rats to discriminate between amplitude-modulated (AM) sounds. Water-deprived rats were exposed to two sounds, and licking a spout during the presentation of one of the two (S+) was rewarded with water, while licking during the other (S-) was not. The AM depth was 100, 60 or 20%. Rats were trained to discriminate between 100 and 60% AM sounds over 2 consecutive days. On the next day, the performance in discriminating between 60 and 20% AM sounds was evaluated. Of the four possible combinations of stimuli, a good performance was observed only when the relationship between S+ and S- regarding the AM depth was kept constant throughout the experiments, indicating that the relationship regarding the AM depth was the cue used by the rats for the discrimination.

Acoustic Stimulation↗
PubMed2000

Maturation of human fetal responses to airborne sound in low- and high-risk fetuses.

The purpose of the study was to characterize the onset and maturation of airborne sound-elicited responses in low- and high-risk preterm fetuses. In Study 1, a total of 91 low-risk fetuses at 27, 30, 33, and 36 weeks GA received three sound trials at 90, 100, 105 and 110 dB and three no-stimulus control trials. The onset of cardiac acceleration and body movement responses occurred at 30 weeks GA. Maturation of the cardiac response was observed with a decrease in threshold from 105-110 dB at 33 weeks GA to 100-105 dB at 36 weeks GA. In Study 2, the procedure was similar except that the 43 high-risk fetuses at 27, 30 and 33 weeks GA did not receive sounds at 90 dB. For the high-risk fetuses, the onset of cardiac and motor responses also occurred at 30 weeks GA. At 33 weeks GA, those high-risk fetuses subsequently born at term showed an increased magnitude of the cardiac acceleration response compared to low-risk fetuses. The results indicate that both low- and high-risk fetuses begin responding to sounds at the same gestational age. Differential responses observed over gestation in the high-risk group most likely indicate differential functional development of the auditory-response system.

Acoustic Stimulation↗
PubMed2002

Tinnitus in hamsters following exposure to intense sound.

Hamsters were trained with a conditioned suppression/avoidance procedure to drink in the presence of a broadband noise and/or a tone and to stop drinking in the absence of sound. A variety of tones and loudspeaker locations were used during training so that the animals would respond to a sound regardless of its frequency or location. Four groups of animals then had their left ears exposed to a 10-kHz tone at 124 or 127 dB for 0.5, 1, 2 or 4 h. They were then tested for tinnitus by comparing their performance with that of unexposed animals to determine if they behaved as if they perceived a sound when no external sound was present. The groups exposed for 2 and 4 h tested positive for tinnitus whereas those exposed for 0.5 and 1 h did not. The degree of hearing loss produced by the tone exposure was assessed using behavioral and auditory brainstem response (ABR) procedures. A partial dissociation was found between the hearing loss, as estimated by the ABR, and the results of the tinnitus test in that animals exposed for 1 h had the same hearing loss as the 2- and 4-h exposed animals, but did not test positive for tinnitus. This suggests that the positive scores on the tinnitus test were not due to hearing loss. These results are discussed along with those of previous behavioral studies of tinnitus in animals.

Acoustic Stimulation↗
PubMed1997

Acute sensitivity to interaural time differences in the inferior colliculus of a bat that relies on passive sound localization.

Gleaning bats rely on passive hearing to detect and localize terrestrial prey, and display remarkable accuracy in their passive sound localization. This study examines binaural processing in the inferior colliculus (IC) of the pallid bat (Antrozous pallidus), a gleaner that attends to prey-generated noise transients to locate prey. The primary focus is to determine whether neurons in its lateral IC, a region that appears dedicated to passive localization, possess a level of sensitivity to interaural time difference (ITD) sensitivity sufficient to indicate the use of ITDs in sound localization. Such a sensitivity was suspected because the pallid bat is capable of very accurate passive sound localization at the lower end of its audible range, where interaural intensity differences (IIDs) are small and may not provide sufficient spatial information. Because the pallid bat's audible range is too high for neurons to phase-lock to carrier frequencies, neurons were tested with square-wave, amplitude-modulated tones and noise to determine their sensitivity to ITDs in the sound envelope. Their sensitivity to the bat's behaviorally relevant ITD range of +/- 70 micros, and their low average interaural time/ intensity trading ratios (18 micros/dB) suggest that the pallid bat IC may have the greatest ITD sensitivity reported in a high-frequency mammalian auditory system.

Acoustic Stimulation↗
PubMed1998

The effect of gaze eccentricity on perceived sound direction and its relation to visual localization.

This study investigates the influence of eye position on the localization of a free-field sound source by employing a pointing method. While fixating visual targets in various directions, the subjects indicated the perceived direction of a sound source by adjusting the azimuthal angle of a swivel pointer. The perceived sound azimuth shifted consistently opposite to the direction of eccentric gaze. i.e. to the left when gaze was to the right and vice versa. This shift resembled an approximately linear function of horizontal gaze direction. The mean magnitude of the shift was 3.1 degrees when the gaze was 45 degrees to the side (mean slope 0.069 degrees per degree eccentricity in gaze direction). An additional experiment investigated the relation of this effect to visual localization. Using the same method, the shift of perceived visual azimuth was measured as a function of gaze direction. The results indicate a shift in the same direction as the auditory shift (opposite to the direction of eccentric gaze), but with a significantly greater magnitude, which was 5.7 degrees for 45 degrees eccentricity in gaze direction. The perceived shifts of sound direction depending on gaze eccentricity may result from incomplete transformations of the auditory spatial coordinates from a craniocentric to an oculocentric frame of reference within neural maps of space, as has been suggested by previous neurophysiological investigations.

Acoustic Stimulation↗
PubMed1983

Echophonocardiographic study of the initial low frequency component of the first heart sound.

To investigate the genesis of the initial low frequency component of the first heart sound that precedes the high frequency vibrations associated with closure of the atrioventricular valves, echophonocardiograms of 36 persons were recorded. These included 10 normal subjects and 26 patients with various types of heart disease including mitral valve replacement. Electrocardiograms demonstrated normal sinus rhythm in 23 subjects, atrial fibrillation in 9, complete atrioventricular block in 2 and atrial flutter in 2. In the phonocardiogram, the low frequency component of the first heart sound followed the onset of the QRS complex and preceded the first high frequency component of this sound. The low frequency component occurred simultaneously with the beginning of the final fast closing movement of the mitral valve on the echocardiogram and was found both in normal rhythm and in arrhythmias. However, in arrhythmias its intensity varied on a beat to beat basis, being loudest after a short RR interval or when atrial systole occurred very close to the expected time of ventricular systole. In patients in whom apexcardiograms were recorded, the low frequency component was coincident with or very close to the onset of ventricular systole. It is concluded that the low frequency component of the first heart sound represents vibrations caused by contraction of the left ventricle and deceleration of antegrade blood flow across the mitral valve. Neither atrial contraction nor mitral valve tension is necessary for the production of this soft initial component.

Adolescent↗
PubMed2002

Effect of the speed of sound in Sensar acrylic lenses on pseudophakic axial length measurements.

PURPOSE: To evaluate adjusting for the change in sound velocity through an intraocular lens (IOL) to determine axial length measurements in pseudophakic eyes. SETTING: Allergan, Inc., Irvine, California, USA. METHODS: The effect of sound velocity through the Sensar (Allergan) acrylic IOL was evaluated using a previously published methodology. RESULTS: The analysis yielded the correction factors for pseudophakic axial length measurements for Sensar acrylic and SLM-2 silicone (Allergan) IOLs. CONCLUSION: The sound speed for the Sensar acrylic IOL differs significantly from that of PMMA and various silicone materials. Corrections for material sound speed must be made to obtain correct pseudophakic axial lengths.

Acrylic Resins↗
PubMed2003

Lung function interpolation by means of neural-network-supported analysis of respiration sounds.

Respiration sounds of individual asthmatic patients were analysed in the scope of the development of a method for computerised recognition of the degree of airways obstruction. Respiration sounds were recorded during laboratory sessions of allergen provoked airways obstruction, during several stages of advancing obstruction. The technique of artificial neural networks was applied for relating sound spectra and simultaneously measured lung function values (spirometry parameter FEV(1)). The ability of feedforward neural networks was tested to interpolate obstruction levels of FEV(1)-classes of which no members were included in the set used for training a network. In this way, a situation was simulated of an existing network recognising a new asthmatic attack under the same physiological conditions. It appeared to be possible to interpolate FEV(1) values, and it is concluded that a deterministic relationship exists between sound spectra and lung function parameter FEV(1). Variance optimisation appeared to be important in optimising the neural network configuration.

Asthma↗
PubMed2004

Changes in evoked potentials during the action of sound signals with different localizing characteristics.

This report presents results of studies of the phenomenon of mismatch negativity (MMN) during exposure to four blocks of sound stimuli each containing identical standards creating an immobile sound image located along the midline of the head and one of a set of deviants, creating a sound image located either by the left ear or moving from the midline of the head towards the left ear or in the opposite direction. All deviants induced mismatch negativity; the minimal amplitude and longest latent period were seen in the mismatch negativity produced by the deviant modeling movement of the sound image from the midline of the head to the left ear. The question of the appearance of mismatch negativity as a criterion for the accurate discrimination of signals with different localizing characteristics is discussed.

Acoustic Stimulation↗
PubMed1997

The influence of respiratory sounds on breathlessness in children with asthma: a symptom-perception approach.

The discordance between the objective and subjective symptoms of asthma has major effects on proper medication and management. In 2 studies the influence of respiratory sounds in the process of symptom perception underlying breathlessness was investigated in children aged 7-17 years. In Experiment 1, asthmatic wheezing sounds were recorded in 16 children during histamine-induced airway obstruction. Breathlessness correlated significantly with rank order of amount of wheezing, but not with lung function. In Experiment 2, after standardized physical exercise, 45 asthmatic and 45 nonasthmatic children were randomly assigned to (a) false feedback of wheezing, (b) quiet respiratory sounds, or (c) no sound. Asthmatic children reported significantly more breathlessness in the 1st versus the 3rd condition. In conclusion, many asthmatic children were easily influenced by wheezing in their estimation of asthma severity, reflected in breathlessness.

Adolescent↗
PubMed2004

Temporal ventriloquism: sound modulates the flash-lag effect.

A sound presented in close temporal proximity to a visual stimulus can alter the perceived temporal dimensions of the visual stimulus (temporal ventriloquism). In this article, the authors demonstrate temporal ventriloquism in the flash-lag effect (FLE), a visual illusion in which a flash appears to lag relative to a moving object. In Experiment 1, the magnitude and the variability of the FLE were reduced, relative to a silent condition, when a noise burst was synchronized with the flash. In Experiment 2, the sound was presented before, at, or after the flash (+/- approximately 100 ms), and the size of the FLE varied linearly with the delay of the sound. These findings demonstrate that an isolated sound can sharpen the temporal boundaries of a flash and attract its temporal occurrence.

Auditory Perception↗
PubMed1988

Sound localization in a predatory rodent, the northern grasshopper mouse (Onychomys leucogaster).

A comparison of the ability of mammals to localize sound revealed that among the animals examined to date, none of the rodents have been able to localize as accurately as the carnivores. Because all of these rodents are prey animals, the question arises as to whether their poor localization acuity is a phyletic trait of Rodentia or whether it is a trait common to prey species that may be under less selective pressure than predators to localize sound accurately. To answer this question, sound localization acuity was determined in a species that is both predatory and a rodent, the northern grasshopper mouse. Localization thresholds for a single 100-ms noise burst were determined for three grasshopper mice using a conditioned avoidance procedure. Their 50% discrimination threshold of 19 degrees is larger than that of any of the previously tested carnivores and well within the range of other rodents. However, calculations of the binaural sound localization cues available to rodents (based on their head size) suggest that the grasshopper mouse may make more efficient use of the available locus cues than other rodents. Thus, although the grasshopper mouse cannot localize as accurately as carnivores, it appears to be more accurate than predicted for a nonpredatory rodent of its size.

Animals↗
PubMed1999

Sound localization in an Old-World fruit bat (Rousettus aegyptiacus): acuity, use of binaural cues, and relationship to vision.

The passive sound-localization acuity of Egyptian fruit bats (Rousettus aegyptiacus) was determined using a conditioned-avoidance procedure. The mean minimum audible angle for left-right discrimination for 3 bats was 11.6 degrees--very near the mean for terrestrial mammals. The bats also were able to localize low- and high-frequency pure tones, indicating that they can use both binaural phase-difference and binaural intensity-difference cues to localize sound. Moreover, they were able to use the binaural phase-difference cue up to at least 5.6 kHz, which is higher than other mammals yet tested. The width of the Egyptian fruit bats' field of best vision was 27 degrees. This value is consistent with the hypothesis that the role of passive sound localization is to direct the eyes for visual scrutiny of sound sources. Thus, the passive localization abilities of these echolocating megachiropteran fruit bats do not deviate from the patterns established for nonecholocating mammals.

Animals↗