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At least 1,153 records · Page 64Linked to original sources
PubMed1993

The role of vision in sound localization.

Three experiments examined the role of vision in locating a brief sound (2-sec. speech noise) from an unseen source in the horizontal left front quadrant. The head could be freely moved. Subjects could point to the sound location more accurately with eyes open. However, since in a second study the accuracy of pointing a finger was poorer than for aiming one's eyes at the sound, the effect in the first study may reflect using vision to calibrate the hand location. A third study showed no difference in accuracy of aiming one's eyes at a sound when eyes were open versus closed during presentation of sound. More accurate auditory localization with eyes open than closed was not supported.

Adolescent↗
PubMed1998

Laboratory studies of a sound system that maintains wakefulness.

Two studies investigated the effects of a waking sound that enhances wakefulness. Study I investigated the effect of the sound level and Study 2 the effect of time and frequency variability of the sound. The recordings of EEG and subjective ratings were analysed to study the effect upon wakefulness. The waking effect increased when sound varied in duration and frequency. A number of specific conditions necessary for the waking effect are described. The exposure should be based on high frequency sounds and several tones chosen to produce disharmony. The exposure should be loud enough to be heard over the masking background noise. The duration and tonal quality should be variable from one presentation to another.

Accidents, Traffic↗
PubMed1983

Sound localization in subjects with impaired hearing. Spatial-discrimination and interaural-discrimination tests.

In order to get a systematic picture of how various hearing impairments and neurologic disorders may affect sound localization, psychophysical spatial- and lateralization-discrimination measurements were performed on 140 subjects, including 69 with different types of hearing impairments, 32 with neurological diseases, and 39 with normal hearing. The quantities measured were: in the freefield, the horizontal minimum audible angle (MAA) at eight reference azimuths around the head and the vertical MAA straight ahead; with headphones, the just-noticeable difference (JND) in interaural time delay and the JND in interaural intensity difference. The standard stimulus was broadband (0.25-10 kHz), pulsed (1-sec), noise presented at a suprathreshold level for both ears (65-100 dB SPL). The results show that there exist characteristic impairments of sound localization in the different types of hearing impairments tested. On a general level, the results are consistent with the concept that the localization of sound relies on a decision made by the central auditory system based on a number of cues present in the acoustic signal at the two ears. The cues tested in our study are: 1) the interaural time difference, 2) the interaural intensity difference, and 3) the spectrum of the received signal at each ear. At a more specific level, the sound localization impairments found in conductive hearing losses are interpreted as bone-conduction effects, the results found in sensorineural hearing losses are interpreted as consequences of impaired or preserved spectral processing, the results in neurinomas are interpreted as impaired signal transmission in the auditory nerves, and the results of subjects with central involvements suggest that separate processors exist at some level in the central auditory system for the different localization cues. Finally, comments are made about the practical clinical significance of sound localization tests in the audiological and neurological evaluation of patients.

Adolescent↗
PubMed1997

Processing of complex sounds in the auditory cortex of cat, monkey, and man.

One of the fundamental features in the organization of sensory cortices which has emerged from 30 years of research in the visual system is the existence of multiple representation of the sensory world in the cerebral cortex. Compared with the visual system much less information exists about the functional specialization of multiple maps in the central auditory system. This is surprising, since an understanding of central auditory representations seems necessary for an understanding of higher auditory processing, including the perception of speech and the perception of auditory space. We have recorded single neuron activity in higher areas of auditory cortex of cats and rhesus monkeys. In cats, activity was recorded in the caudal part of the anterior ectosylvian (AE) cortex (areas AEA and AAF). More than half of the neurons were clearly tuned to the location of a sound source in azimuth and elevation. Frequency-modulated (FM) sounds elicited best responses at fast rates of modulation. By contrast, neurons in the posterior ectosylvian (PE) areas (PAF, VPAF) responded better to slow FM rates. This suggests a possible specialization for the processing of spatial attributes in the AE cortex, and a possible preference for auditory "patterns" in PE. In macaque monkeys, we explored the question of parallel processing in the higher auditory pathways by combining lesion and anatomical tracer techniques with single unit recording. Inactivation of primary auditory cortex (AI) abolished pure-tone responses in the caudomedial area (CM), but not in the rostral area (R). Injections of retrograde fluorescent tracers into R showed strong labeling of the main, ventral nucleus of the medial geniculate (MGv). Both findings suggest the existence of parallel pathways in the auditory cortex, originating at more peripheral sites and possibly specialized for the processing of auditory space vs. auditory patterns. The auditory pattern pathway in Macaque auditory cortex was further explored by using complex stimuli including Macaque-specific communication sounds. Neurons in the lateral belt areas (AL, ML, and CL) respond very selectively to bandpassed noise stimuli, to FM sounds of a certain rate and direction, as well as to certain classes of monkey calls. We are now in the process of exploring higher areas of human auditory cortex by measuring cortical activation with noninvasive functional magnetic resonance imaging (fMRI) while stimulating with complex auditory sounds.

Animals↗
PubMed1997

Comparative study of sound localization and its anatomical correlates in mammals.

One of the fundamental features of hearing is the ability to localize the sources of sounds, particularly brief sounds, which may warn of nearby animals. Yet not all mammals localize sound equally well with threshold acuity ranging from about 1 degree for elephants and humans to more than 25 degrees for gerbils and horses and a near absence of localization in some subterranean species. During the past decade evidence has accumulated that this variation cannot be accounted for simply by the availability of the physical cues for locus. Nor does it appear to be a function of an animal's lifestyle. Rather sound-localization acuity in mammals appears to be a function of the precision required of the visual orienting response to sound. Thus the neural integration of hearing and vision in cortex, as well as in multimodal subcortical structures, is a reflection of their behavioral integration and evolutionary coupling.

Animals↗
PubMed1989

Perception of mechanical heart valve sounds.

Most currently used mechanical heart valve prostheses generate a distinct sound when they close. This sound is sometimes disturbing to the patient, and may impair quality of life. In a study of 285 patients followed up for a mean of 2.5 years after mechanical heart valve replacement, one-third were sometimes disturbed by sounds emanating from the prosthesis. Older patients were less disturbed than young ones, but whether this could be explained by age-related impairment of hearing ability (presbyacusis) was not possible to determine. Prosthetic size, implantation site, patient's weight, body surface area and type of prosthesis did not statistically differ according to experience of prosthetic sounds. Although few patients were seriously disturbed by these sounds, it is hoped that mechanical heart valves of the future will function more quietly.

Age Factors↗
PubMed1990

Perception of the relative distances of nearby sound sources.

The pressure of a sound varies systematically with a listener's distance from a sound source, providing a useful cue for perceiving changes in the distance between a listener and a sound-producing object. The pressure-discrimination hypothesis predicts that thresholds for discriminating changes in distance are constrained by the underlying ability to discriminate the resulting changes in sound pressure--specifically, that the smallest discriminable change in distance should be about 5% of the reference distance. Previous studies reported thresholds of about 5% for reference distances greater than a few meters but surprisingly worse thresholds for closer reference distances. In the present study, thresholds at two close distances, 1 and 2 m, were within the 5% range predicted from the pressure-discrimination hypothesis. Moreover, thresholds were significantly worse in a control condition in which the pressure cue was removed. Results of previous studies were adjusted to take into account the possibility of conservative response tendencies by the subjects. These adjusted findings agree well with the results of the present study and the pressure-discrimination hypothesis. It is concluded that variations in sound pressure are very useful for perceiving changes in listener-source distances, even at close distances.

Adult↗
PubMed1998

[Preference for high frequency sounds of contact calls in primates: Japanese macaques and ringtailed lemurs].

Preference for high frequency sounds in human infants are found by other researchers. The purpose of this study is to examine whether nonhuman primates also have the same tendency as human infants. It is important to consider language origins. Two types of tape recorded coo calls, contact calls, with high and low fundamental frequencies were played back as stimuli for two groups of Japanese macaques (Macaca fuscata). The result showed that the animals of both groups preferred high frequency sounds. To ascertain whether other species also have the same tendency as the Japanese macaques, a playback experiment similar to that for Japanese macaques was conducted for one group of ringtailed lemurs (Lemur catta). Tape recorded mew calls, contact calls, were used as stimuli. The results showed that ringtailed lemurs also preferred high frequency sounds. Moreover, it was clarified by an additional playback experiment for one group of Japanese macaques that animals had an affective preference for high frequency sounds. These results suggest that nonhuman primates have a consistent tendency to prefer high frequency sounds.

Acoustic Stimulation↗
PubMed1990

[An acoustical study on the TMJ sounds].

For the purpose of investigating to clarify the differential diagnosis and treatment of TMJ dysfunction, The TMJ sounds were analysed acoustically using accelerometers. The 101 TMJ sounds were recorded from 20 patients. Jaw movement and electromyogram (EMG) were recorded simultaneously. Comparison of the TMJ sounds to the jaw movement and EMG were made. The following conclusions were obtained: (1) TMJ sounds were classified into three clusters according to the total energy and band width. (2) It is possible to divide the changing of jaw moving velocity into three patterns. (3) It was found that the signal characteristics have relevance to the changing patterns of jaw moving velocity. (4) The acoustical study of TMJ sounds bring on the variable informations to clinical dentistry.

Acoustics↗
PubMed1999

Coding of sound envelopes by inhibitory rebound in neurons of the superior olivary complex in the unanesthetized rabbit.

Most natural sounds (e.g., speech) are complex and have amplitude envelopes that fluctuate rapidly. A number of studies have examined the neural coding of envelopes, but little attention has been paid to the superior olivary complex (SOC), a constellation of nuclei that receive information from the cochlear nucleus. We studied two classes of predominantly monaural neurons: those that displayed a sustained response to tone bursts and those that gave only a response to the tone offset. Our results demonstrate that the off neurons in the SOC can encode the pattern of amplitude-modulated sounds with high synchrony that is superior to sustained neurons. The upper cutoff frequency and highest modulation frequency at which significant synchrony was present were, on average, slightly higher for off neurons compared with sustained neurons. Finally, most sustained and off neurons encoded the level of pure tones over a wider range of intensities than those reported for auditory nerve fibers and cochlear nucleus neurons. A traditional view of inhibition is that it attenuates or terminates neural activity. Although this holds true for off neurons, the robust discharge when inhibition is released adds a new dimension. For simple sounds (i.e., pure tones), the off response can code a wide range of sound levels. For complex sounds, the off response becomes entrained to each modulation, resulting in a precise temporal coding of the envelope.

Acoustic Stimulation↗
PubMed1990

Comparing RCPs to physicians for the description of lung sounds: are we accurate and can we communicate?

UNLABELLED: Precise communication among clinicians of chest-auscultation findings depends on use of standardized nomenclature for lung sounds. To identify the current practice of clinicans in describing lung sounds, we surveyed physicians and respiratory care practitioners (RCPs). MATERIALS AND METHOD: Surveys were specifically designed to identify: (1) whether RCPs and physicians use similar terms to describe adventitious lung sounds (ALS), (2) whether changes are occurring in response to the recommendations of the ATS-ACCP Ad Hoc Subcommittee on Pulmonary Nomenclature, and (3) whether RCPs and physicians differ in their ability to accurately recognize ALS. We surveyed 156 RCPs at the 1987 Annual Meeting of the American Association for Respiratory Care and 223 pulmonary physicians (PPs) and 54 nonpulmonary physicians (NPPs) at the 1988 Annual Meeting of the American College of Chest Physicians. Each survey participant was required to listen to five examples of ALS using earphones and an audiocassette player and then to write 'free-form' descriptions of what they heard. (All participants listened to the same ALS.) RESULTS: Fine crackles and high-pitched monophonic and polyphonic wheezes were readily recognized by the majority of RCPs and physicians. Fine crackles were described as rales or crackles; high-pitched, monophonic wheezes were described as stridor or wheezes; however, high-pitched, polyphonic wheezes were usually described as wheezes. RCPs and physicians used a variety of terms to describe coarse crackles and rhonchi. The term rhonchi was frequently used inappropriately by all groups surveyed. There were no significant differences between PPs and RCPs in their ability to accurately recognize adventitious lung sounds; however, PPs were superior to NPPs (p less than 0.05) in this regard. PPs were superior to RCPs and NPPs (p less than 0.05) in appropriately using the term 'fine' for the description of crackles. CONCLUSION: All three groups of clinicians need to improve their ability to recognize and describe lung sounds.

Allied Health Personnel↗
PubMed1999

[Changes in tracheal and lung sounds before and after resection of adenoid cystic carcinoma of the trachea].

A 79-year-old woman was admitted to our hospital with complaints of wheezing and dyspnea. Adenoid cystic carcinoma was diagnosed from the findings on biopsy specimens obtained by fiberoptic bronchoscopy. The tumor was resected and end-to-end anastomosis was performed. Precision analyses of lung sounds were conducted before and after the operation. During eupnea the tracheal sounds prior to operation contained an accentuated, high-frequency component at about 1,500 Hz. The tracheal sounds included a single monophonic wheeze during deep inspiration and 5 wheezes during forced expiration. By contrast, lung sounds in the chest wall were almost normal both before and after the operation. We concluded that increases in high-frequency components in tracheal sounds and the manifestation of various wheezes can be useful in diagnosing tracheal stenosis and/or tumors.

Aged↗
PubMed2000

[Auditory analysis of the sound source approaching and withdrawing: psychoacoustic and neurophysiological correlates].

The findings seemed to be based on direction and velocity of modelling the radial sound source shifting in free acoustic field. The threshold and the optimal parameters of the acoustic model imitating the approaching and withdrawing of the sound source shifting in silence and under conditions of noise, were established. A correlation between peak-to-peak amplitudes of the N1-P2 components of auditory EPs and the imitated direction of the sound shifting, was shown. The role of different left and right hemispheres' areas in perception of the radial sound source was analysed. The detector features of the central auditory neurones were shown as a possible mechanism of estimating the sound source approaching and withdrawal.

Acoustic Stimulation↗
PubMed2001

Recreational scuba divers' aversion to low-frequency underwater sound.

Increasing use of active low-frequency sonar by submarines and ships raises the risk of accidental exposure of recreational divers to low-frequency underwater sound (LFS). This study aimed to characterize the subjective responses of recreational scuba divers to LFS to ascertain the extent to which LFS may impact their enjoyment, comfort, or time spent underwater. Seventeen male and nine female recreational scuba divers participated. Diving was conducted in an acoustically transparent tank located within a larger anechoic pool. Subjects wore scuba gear and were positioned I m below the surface in a prone position. The sound transducer was located 4 m directly below the diver's head. Sound exposures consisted of three signal types (pure tone, 30 Hz hyperbolic sweep up, and 30 Hz hyperbolic sweep down) each presented at six center frequencies from 100 to 500 Hz and six sound pressure levels(SPL) ranging from 130 to 157 dB re 1 microPa. The duration of each sound exposure was 7 s. Subjects responded via an underwater console to rate aversion to LFS on a category-ratio scale, and to indicate the presence or absence of vibration of any body part. Aversion to LFS and the percent incidence of vibration increased as the SPL increased. The percent incidence of vibration decreased linearly with increasing frequency. At the highest SPL the probability that an aversion rating would exceed Very Severe (7 on the category-ratio scale) was predicted to be 19%. There was no significant difference in aversion among signal types. The 100 Hz frequency was the most aversive frequency (P < 0.05). A plot of aversion vs. frequency showed a U-shaped function with minimum aversion at 250 Hz. In conclusion, diver aversion to LFS is dependent upon SPL and center frequency. The highest aversion rating was given for 100 Hz, this frequency corresponded with the greatest probability of detecting vibration. Factors other than vibration seem to account for aversion to the highest frequencies. Our data suggest that LFS exposures up to 145 dB re 1 microPa at frequencies between 100 and 500 Hz will have minimal impact on the recreational diver.

Adult↗
PubMed1998

[Instantaneous power maxima and power spectrum maxima analysis of second heart sounds signals].

We employed the time-frequency analysis to the processing of the second heart sound signals and studied the time-frequency spectrum of the normal and abnormal second heart sound. According to the time marginal and frequency marginal, we made the instantaneous power maxima and power spectrum maxima of the second heart sounds, which were thought as the quantity index about physiology and pathology. The results showed that the time-frequency spectrum of the second heart sounds gave a whole comprehensive description to dynamic course of the signals. The instantaneous power maxima and power spectrum maxima contain the time varying information in the second heart sound.

Heart Sounds↗
PubMed2002

[Changes of evoked potentials caused by sound signals with different localization characteristics].

Characteristics of the mismatch negativity (MMN) were studied by presenting the subjects with four blocks of stimuli containing standard series of clicks (90%) simulating a stationery sound image located in the head midline, and one of three different deviant series of clicks (10%) simulating either a stationary sound image located near the left ear or a moving sound image which shifted from the head midline to the left ear or in the opposite direction. All the deviant stimuli elicited the MMN with the minimal peak amplitude and the greatest latency evoked by the deviant series of clicks simulating the sound image moving from the head midline to the left ear. These findings suggest that the MMN may be considered as a pre-perceptual physiological measure of the discrimination accuracy for the sound signals with various spatial locations.

Acoustic Stimulation↗
PubMed1999

[Computer-aided teaching system of heart sound].

This paper details a full set of plan of the computer-aided teaching of heart sound. By means of digital sound technology one is capable of playing realistically heart sound of various kinds based on database. Each heart sound is demonstrated by a proper explanation of its characteristics and a heart sound graph. This method gets over the shortages of traditional teaching methods. Besides, this system can be used to test users' level of auscultation.

Computer Systems↗
PubMed2003

[Spectral characteristics of vowel-like sounds in children of the first year of life and speech development].

To study the continuity in speech development, an investigation of vowel-like sounds recorded in the course of longitudinal research of speech formation was carried out in 12 infants beginning with the first month up to 12 months of their life. It was revealed that features ensuring separation of vowel-like sounds are specific by their amplitude relation and frequency location of the most expressed spectral maxima, including the maxima corresponding to the fundamental frequency. As fundamental frequency increased, the vowel-like sounds [a], [u], [i] began to exhibit specific changes of the amplitude ratios of the spectral maxima. It was established that peculiarities of frequency positions of spectral maxima and relations of their amplitudes may be the very features on the bases of which children compare their own vowel-like sounds to the vowels of the adults in sound imitation. These findings and literature data corroborated the opinion of continuity in speech development, beginning with the early preverbal vocalizations.

Adult↗