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PubMed1981

Development of responsiveness to suprathreshold acoustic stimulation in chickens.

Developmental changes in an unconditioned response to acoustic stimulation were observed in young chickens. Specifically, durations of distress call (peep) suppression were measured after the onsets of tones that differed in intensity and frequency in 384 newly hatched and 4-day-old chicks. Resuppression was also measured after a 6% change in the frequency of these tones, once the animals had habituated to the original tone. The data showed that the suppression varied systematically as a function of age, intensity, and frequency: (a) the duration of suppression increased with increasing stimulus intensity, as expected; (b) responsiveness to high frequencies grew more rapidly over the first 4 days than responsiveness to low frequencies, an effect indicating a developmental gradient across frequencies with age; (c) resuppression to the 6% change in frequency increased in duration with age; and (d) young birds suppressed vocalizations longer to loud tones in the range of their species' maternal assembly call than to other frequency-intensity combinations. These developmental trends indicate rapid changes in "perceived loudness" and "perceptual sharpening" over the first few days of postnatal life.

Acoustic Stimulation↗
PubMed1977

Minimum auditory movement angle: binaural localization of moving sound sources.

In the first experiment, subjects were asked to discriminate whether a sound was emanating from a moving or stationary source. The minimum audible movement angle (MAMA) thus defined was observed to increase as the source velocity increased. MAMA ranged from a low of 8.3 degrees with the slowest velocity employed (90 degrees/s) to a high of 21.2 degrees with the fastest velocity (360 degrees/s). In the second experiment, subjects were asked to localize where the moving source was, at signal on and offset. The results indicate that the apparent onset is displaced in the direction of motion and the amount of this displacement is directly related to source velocity. Less consistent results were observed with signal offset. The present results suggest that the binaural system is relatively insensitive to motion.

Adult↗
PubMed1984

Short-latency auditory responses obtained by cross correlation.

Short-latency auditory responses were derived by cross correlation of pseudorandom white noise with averaged scalp potentials in guinea pigs. The cross-correlation functions were characterized by distinct cochlear microphonic and neural components, as distinguished by susceptibility to hypothermia and masking noise. This technique detects only linear, frequency-following responses of the auditory system, and demonstrated neural frequency following up to 3-4 kHz; thresholds were about 30-40 dB spectrum level. While conventional auditory brain stem responses reflect onset neural activity and are most responsive to high-frequency stimuli, cross-correlation responses reflect frequency-following activity, primarily to low frequencies, and thus may represent a complementary method of electrophysiologic assessment of the auditory system. Data are very rapidly acquired, and estimation of responses of limited areas of the cochlea may be possible by off-line digital filtering of cross-correlation functions obtained with broadband noise stimuli.

Animals↗
PubMed1985

Postnatal development of physiological responses in auditory nerve fibers.

The discharges of auditory nerve fibers in kittens 4-37 days of age were recorded from micropipette electrodes. Tuning curves, thresholds, and the degree of tuning (Q 10) are compared over this age range. The tuning curves for fibers during the first postnatal week are relatively flat, with thresholds above 100 dB SPL. The response areas of VIII-nerve fibers during this period are restricted to low-to-middle frequencies. With increasing age there is a reduction in threshold and an increase in the sharpness of tuning which is dependent on fiber CF. Response characteristics similar to adult VIII-nerve fibers were observed first for fibers with CFs near 5 kHz. For the response measures used here, VIII-nerve fibers in kittens are adultlike by the third to fourth postnatal week. The results are discussed in relation to the morphological development of the cochlea reported by other investigators.

Aging↗
PubMed1985

Auditory brain stem responses from human infants: pure-tone masking profiles for clicks and filtered clicks.

The effects of simultaneous pure-tone maskers on ABR wave V latency and amplitude were examined in three-month-old infants as a means of delineating the frequency specificity of these responses in the immature auditory system. Masking profiles at two intensities (60 and 40 dBn HL) were obtained for click, as well as 4000- and 1000-Hz filtered-click stimuli. Infant profiles, obtained by measuring both latency and amplitude shifts as a result of the discrete-frequency maskers, were compared to adult data obtained under an identical masking paradigm. Both latency and amplitude analyses showed masking profiles for infants which reveal greater low-frequency contribution to responses than found in adult profiles. Additionally, the infant profiles reveal clear differences in the degree of high-frequency spread of masking when comparisons are made to the adult data.

Auditory Perception↗
PubMed1991

An evaluation of eight computer models of mammalian inner hair-cell function.

Eight computer models of auditory inner hair cells have been evaluated. From an extensive literature on mammalian species, a subset of well-reported auditory-nerve properties in response to tone-burst stimuli were selected and tested for in the models. This subset included tests for: (a) rate-level functions for onset and steady-state responses; (b) two-component adaptation; (c) recovery of spontaneous activity; (d) physiological forward masking; (e) additivity; and (f) frequency-limited phase locking. As models of hair-cell functioning are increasingly used as the front end of speech-recognition devices, the computational efficiency of each model was also considered. The evaluation shows that no single model completely replicates the subset of tests. Reasons are given for our favoring the Meddis model [R. Meddis, J. Acoust. Soc. Am. 83, 1056-1063 (1988)] both in terms of its good agreement with physiological data and its computational efficiency. It is concluded that this model is well suited to provide the primary input to speech recognition devices and models of central auditory processing.

Animals↗
PubMed1994

Effects of frequency and amplitude modulation on the pitch of a complex tone with a mistuned harmonic.

It has previously been found that when a single low-numbered harmonic of a complex tone is progressively mistuned, for mistunings up to about 3%, the pitch of the complex changes in the direction of the mistuning but for larger mistunings (by about 8%) the pitch returns to its original value. This result is compatible with the operation of a mechanism such as a graded harmonic sieve, which can reject from the calculation of pitch those frequency components that are implausibly distant from a harmonic frequency. The first experiment shows that the tolerance of such a sieve is increased when all the components of the complex tone (including the mistuned component) share a common pattern of frequency modulation at a rate of 6 Hz. The second experiment shows that the tolerance of the sieve is not increased when the components share a common pattern of amplitude modulation at 17 Hz. The third experiment replicates these findings and further shows that the increase in sieve tolerance for FM, but not for AM, occurs at both 6 and at 17 Hz.

Acoustic Stimulation↗
PubMed1995

Interference in detection of interaural delay in a sinusoidally amplitude-modulated tone produced by a second, spectrally remote sinusoidally amplitude-modulated tone.

Sensitivity to interaural time delays (ITDs) within high-frequency sinusoidally amplitude-modulated (SAM) target tones was measured in the presence of a second, spectrally remote diotic SAM tone (termed an interferer). Targets and interferers were 100% modulated at 250 Hz and each was presented at 77 dB SPL for a duration of 250 ms. The modulations of targets and interferers were either in-phase or out-of-phase. In the first experiment, when the target SAM tone was centered at 4 kHz, interferers were centered at either 500 Hz, 1 kHz, or 2 kHz. Threshold ITDs were substantially increased in the presence of the interferers as compared to when the targets were presented in isolation. The greatest effects were observed with interferers centered at 500 Hz and 1 kHz. In the second experiment, when the target SAM tone was centered at 2 kHz, interferers were centered at either 500 Hz or 4 kHz. Threshold ITDs increased in the presence of either interferer, but the greatest increase occurred in the presence of the 500-Hz SAM tone. In the third experiment, it was found that presenting the low-frequency SAM tones continuously resulted in less interference than did presenting the interferers and targets coincidently. In all three experiments, the effects produced by the interferers did not depend upon whether they were modulated in-phase or out-of-phase with the target. Taken together, the data argue against the notion that the interference could result from a peripheral, monaural interaction between target and interferer waveforms.

Auditory Perception↗
PubMed1997

Detection of increments and decrements in sinusoids as a function of frequency, increment, and decrement duration and pedestal duration.

Thresholds for the detection of increments and decrements in level of 70 dB SPL sinusoidal signals were measured as a function signal duration (10, 20, or 200 ms), pedestal duration before the signal (10 ms, 200 ms, or pedestal on continuously) and frequency (250, 1000, or 4000 Hz). The sinusoids were presented in a low-pass filtered background noise with an overall level of 68-69 dB SPL which had two purposes: (1) to mask spectral splatter; (2) to induce an adaptation effect, which caused the continuous 4000-Hz pedestal (but not the other two pedestals) to decay to inaudibility (adaptation). We were particularly interested in determining whether the difference in noise-induced adaptation across frequency would influence the pattern of results. Seven normal-hearing subjects were used. Thresholds improved with increasing frequency and with increasing duration for both increments and decrements. However, the effect of increment/decrement duration decreased with increasing frequency; at 4000 Hz thresholds were almost the same for increment durations of 10 and 20 ms. The energy of the increments at threshold increased markedly with increasing increment duration (especially from 20 to 200 ms), suggesting a dominant role for the onsets of the increments as opposed to ongoing differences in level. Increasing the pedestal duration before the increment from 10 to 200 ms slightly improved thresholds for increment and decrement durations of 10 and 20 ms. Increment thresholds were similar for the gated and continuous pedestals at all frequencies, even though the 4000-Hz continuous pedestal decayed to inaudibility. However, thresholds for 200-ms increments were somewhat lower for continuous than for gated pedestals, and supplementary experiments found a larger gated-continuous difference for pedestals presented in quiet. Making the pedestal continuous adversely affected performance for the 10- and 20-ms decrements, but not for the 200-ms decrement. We suggest that the results for decrement detection may be affected by neural long-term adaptation, although they are not clearly related to loudness adaptation.

Adult↗
PubMed1998

Factors related to magnitude estimation scaling of complex auditory stimuli: aging.

The purpose of this study was to examine the effects of aging on magnitude estimation scaling of the loudness of complex auditory stimuli in the form of rock music. The subjects were 10 young adults (M age = 19.3 yr.), and 10 older individuals (M age = 54.2 yr.). The older individuals' mean numerical responses suggested that they perceived the rock music stimuli as louder for all nine suprathreshold intensities tested. The older group of subjects may have perceived the suprathreshold stimulus intensities as being louder because of physical and affective changes that naturally occur in central auditory processing during the aging process.

Acoustic Stimulation↗
PubMed1984

A comparison of variability among measurements of subjective tinnitus and objective stimuli.

8 patients with subjective tinnitus were trained in pitch-matching, loudness-matching, and simultaneous-masking tasks using narrow-band noise and/or pure-tone stimuli. Extensive pitch-matching, loudness-matching and masking measurements were then obtained for their tinnitus, after which the same measurements were obtained for objective stimuli which approximated the frequency and intensity of the tinnitus. Variability for pitch and loudness matching to tinnitus was extremely large relative to the same measurements for objective stimuli. This was particularly true for pitch-matching where even the most consistent patients showed variability for matches to their tinnitus which was an order of magnitude greater than for matches to objective stimuli in the same frequency region. No evidence of frequency-specific masking of tinnitus was seen in any of the patients although such evidence was obtained for the masking of objective stimuli. The results suggest that the large variability in matches to tinnitus, and the lack of normal frequency-specific masking of tinnitus in these patients may reflect interactions at levels higher than the end-organ rather than a degradation in peripheral auditory function.

Auditory Perception↗
PubMed1986

[Responses of neurons of the parietal association cortex of the cat to acoustic stimulation before and after suppression of the auditory cortex in the cat].

The aim of this work was to study the influence of auditory cortex suppression in cat on response patterns of the parietal associative cortex neurons responding to different frequency tones. Suppression was performed by two methods: bilateral isolation and application of 6% nembutal solution on the cortex surface. Frequency-thresholds curves were plotted for all neurons studied. Prior to suppression the majority (84%) of studied neurons had one or two characteristic frequencies. After suppression the percentage of such cells fell to 63% of all responding neurons. Frequency range to which neurons could respond was altered as well. Normally almost all neurons tested could respond to a wide spectrum of presented frequencies. After suppression 69% of neurons did not respond to tones above 8-10 kHz. This may indicate that mainly information about high frequency tones is transmitted via the auditory cortex. The possibility that associative thalamic nuclei are the main source of acoustic information for parietal associative cortex neurons is discussed.

Animals↗
PubMed2004

Neuropsychology: pitch discrimination in the early blind.

Do blind people develop superior abilities in auditory perception to compensate for their lack of vision? They are known to be better than sighted people at orientating themselves by sound, but it is not clear whether this enhanced awareness extends to other auditory domains, such as listening to music or to voices. Here we show that blind people are better than sighted controls at judging the direction of pitch change between sounds, even when the speed of change is ten times faster than that perceived by the controls--but only if they became blind at an early age. The younger the onset of blindness, the better is the performance, which is in line with cerebral plasticity being optimal during the early years.

Acoustic Stimulation↗
PubMed2003

Cochlear compression: perceptual measures and implications for normal and impaired hearing.

This article provides a review of recent developments in our understanding of how cochlear nonlinearity affects sound perception and how a loss of the nonlinearity associated with cochlear hearing impairment changes the way sounds are perceived. The response of the healthy mammalian basilar membrane (BM) to sound is sharply tuned, highly nonlinear, and compressive. Damage to the outer hair cells (OHCs) results in changes to all three attributes: in the case of total OHC loss, the response of the BM becomes broadly tuned and linear. Many of the differences in auditory perception and performance between normal-hearing and hearing-impaired listeners can be explained in terms of these changes in BM response. Effects that can be accounted for in this way include poorer audiometric thresholds, loudness recruitment, reduced frequency selectivity, and changes in apparent temporal processing. All these effects can influence the ability of hearing-impaired listeners to perceive speech, especially in complex acoustic backgrounds. A number of behavioral methods have been proposed to estimate cochlear nonlinearity in individual listeners. By separating the effects of cochlear nonlinearity from other aspects of hearing impairment, such methods may contribute towards identifying the different physiological mechanisms responsible for hearing loss in individual patients. This in turn may lead to more accurate diagnoses and more effective hearing-aid fitting for individual patients. A remaining challenge is to devise a behavioral measure that is sufficiently accurate and efficient to be used in a clinical setting.

Acoustic Stimulation↗
PubMed2005

Evaluation of speech disorders in children with cleft lip and palate.

BACKGROUND: We investigated the reliability of nasopharyngoscopy and auditory perception, two common clinical methods employed in examining the speech pathology of children with cleft lip and palate. PATIENTS AND METHODS: Nasopharyngoscopy was performed to assess velopharyngeal closure function and nasopharyngeal morphology. The auditory examination evaluated nasality and other speech disorders such as articulatory tension, shift in articulation, and sigmatism. The study was based on the audio and video recordings of twelve patients (9.5 +/- 0.5 years) after surgical rehabilitation of their cleft lip and palate. The speech sample consisted of reading a standardized sequence of words. The recordings were analyzed by several examiners with different experience in the evaluation procedure at two time-points. Inter-rater and intra-rater reliability was determined by Cohen's Kappa coefficient and by estimation of the 95% intervals of confidence. RESULTS: Analysis of the visual and auditory-perceptual findings by the experienced raters was highly reliable. However, the less experienced raters' results showed greater variability, as did morphological evaluation in both groups. Comparison between visual and auditory evaluations concerning hypernasality resulted in little correlation. CONCLUSIONS: These two subjective methods of evaluation are recommended because of their high reliability with experienced raters. Our results suggest that "experience" is an essential criterion in determining the structural quality of the morphological and functional assessment of typical speech pathologies in children with cleft lip and palate. In addition, the data demonstrate the necessity of special multidisciplinary rehabilitation teams in so-called cleft centers.

Child↗