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PubMed1994

Ontogenetic variations in auditory arousal threshold during sleep.

Developmental variations in auditory arousal thresholds during sleep were investigated in four groups of normal male subjects--children, preadolescents, adolescents, and young adults. Arousal thresholds were determined during NREM and REM sleep for tones presented via earphone insert on a single night following two adaptation nights of undisturbed sleep. Age-related relationships were observed for both awakening frequency and stimulus intensity required to effect awakening, with awakenings occurring more frequently in response to lower stimulus intensities with increasing age. Although stimulus intensities required for awakening were high and statistically equivalent across sleep stages in nonadults, higher intensity stimuli were required in Stage 4 relative to Stage 2 and REM sleep in adults. These results confirm previous observations of marked resistance to awakening during sleep in preadolescent children and suggest that processes underlying awakening from sleep undergo systematic modification during ontogenetic development.

Adolescent↗
PubMed2006

Loudness summation and the mismatch negativity event-related brain potential in humans.

Abstract Infrequently omitting a sound from a repetitive sequence elicits the mismatch negativity (MMN) ERP response when the stimulus onset asynchrony (SOA) is less than 200 ms. We contrasted two alternative explanations of omission MMN. (1) Each sound starts a separate temporal integration process. Omissions violate the constancy of the temporal structure within the integration window. (2) Sounds preceding an omission are perceived to be louder than those followed by a sound within the integration period, because omissions allow the full stimulus aftereffect to be included in perceived loudness. We varied the SOA between 117 and 217 ms. For this case, the temporal structure explanation predicts that no MMN will be elicited, whereas the loudness summation explanation predicts that MMN will be elicited. MMN was elicited by tone omissions with random SOA, suggesting that loudness summation plays an important role in the elicitation of omission MMN.

Acoustic Stimulation↗
PubMed1984

Sensitivity to light and sound following minor head injury.

9 consecutively referred closed head injury (CHI) patients were assessed for sensitivity to light and sound stimuli, within 7-19 days of injury, on both objective and subjective measures. Patients were matched with controls on age, sex, race, socio-economic status and order of test administration. The mean luminance (1366 lux) tolerated by CHI patients was significantly lower (0.01 level by Student's t-test for related samples) than that tolerated by controls (1783 lux). The mean sound intensity tolerated by CHI patients was also lower (82 db) than for controls (94 db), though this difference was not statistically significant. Subjective ratings of sensitivity made by CHI patients after exposure to intense sound and light stimuli, showed no relationship to objective ratings of tolerance. The results demonstrate an objective basis for complaints of increased sensitivity, at least to light, following CHI. These findings do not support earlier "psychogenic" explanations of post-concussion syndrome (PCS) etiology.

Adolescent↗
PubMed1990

Influence of stimulation parameters on auditory stimulus processing in schizophrenia and major depression: an auditory evoked potential study.

The influence of stimulation frequency and stimulus intensity on the auditory evoked potential components N1 and P2 was investigated in schizophrenic and major depressive patients. The findings in the patients were compared with those in normal controls. At a high stimulation frequency the amplitude of N1 was enhanced in both schizophrenic and major depressive patients; the latency of N1 increased only in the schizophrenic patients. These changes may be related to impairments of auditory input control and processing in these diseases. In the schizophrenic patients, P2 latency was prolonged under treatment with high-potency neuroleptic drugs.

Acoustic Stimulation↗
PubMed2006

Acoustic parameters of snoring sound to compare natural snores with snores during 'steady-state' propofol sedation.

OBJECTIVES: To investigate the acoustic similarity between natural and sedation-induced snores. DESIGN: Prospective observational study. SETTING: University Hospital Aintree, Liverpool, UK. PARTICIPANTS: Twenty-one patients, who had already had overnight snore recordings, completed a pre-operative sleep nasendoscopic examination. Endoscopic examination of the upper aero-digestive tract was performed at sequentially increasing, steady-state sedation levels, using intravenous propofol administered according to a weight/time-based algorithm to predict blood and effect site (tissue) concentrations. At each sedation level at which snoring occurred, snoring sound was recorded. From these samples, snore files, comprising the inspiratory sound of each snore were created. Similarly, from natural snores recorded pre-operatively, snore files, comprising the inspiratory sounds of the first 100 snores with the patient sleeping in a supine position, were also created. MAIN OUTCOME MEASURES: Snore duration (s), loudness (dBA), periodicity (%) and energy ratios for the frequency sub-bands 0-200, 0-250 and 0-400 Hz. RESULTS: Snore loudness increased significantly (P < 0.0001), whilst energy ratios for frequency bands 0-200, 0-250 and 0-400 Hz all decreased significantly as sedation level increased (P < 0.001). A significant difference between natural snoring and snoring induced at the lowest sedation level was shown (P < 0.0001). Endoscopic examination was not tolerated at this sedation level. CONCLUSIONS: The acoustic characteristics of sedation-induced and natural snores are sufficiently different to recommend the need for further research to determine whether the technique of sleep nasendoscopy is, in fact, a valid predictor of outcome of snoring surgery.

Acoustics↗
PubMed1983

Computerized testing of signal-encoding strategies with round-window implants.

After extensive testing of a patient with two bipolar modiolar electrodes connected to a percutaneous plug in 1977, we provided four patients with a single-channel monopolar round-window electrode connected to a tuned radio-frequency receiver coil. Loudness and pitch discrimination and results of psychophysical scaling experiments of extracochlear electrodes are comparable to those with intracochlear stimulation. Extensive testing with a computerized test system and with tape-recorded and live speech material showed that accurate vowel and speaker identification by stimulation alone is possible and that discrimination by lipreading is considerably improved. Interactive training sessions further improve discrimination results. Different signal-encoding algorithms can be used to generate in real time stimulation signals from prestored speech parameters (such as pitch, gain, formants, and zerocrossing intervals).

Adult↗
PubMed1993

Temporal analysis in normal and impaired hearing.

The ear contains an array of filters that separate the components of a complex signal into "channels" tuned to different center frequencies. Temporal analysis can be considered as two processes: analysis of the time pattern occurring within each channel, and comparison of the time patterns across channels. Within-channel acuity can be characterized by tasks such as gap detection, or by the ability to detect amplitude modulation as a function of modulation rate. The smallest detectable gap duration for a white noise stimulus is 2-3 ms. The results can be modeled by an array of filters, with each filter followed by a nonlinearity and a (central) sliding temporal integrator. Hearing impairment of cochlear origin can have adverse effects on temporal resolution because it often reduces the audible bandwidth of the stimuli, and because it results in a reduced sensation level of the stimuli. The sliding temporal integrator appears to be unaffected by hearing loss, although the nonlinearity preceding the integrator may be abnormal, and this can lead to reduced temporal resolution for sounds with slowly fluctuating envelopes. Hearing impairment of more central origin may also adversely affect temporal resolution, but the mechanisms responsible for this are not known. The acuity of across-channel temporal analysis depends on whether the task is one of discrimination or of identification of temporal order. The finest acuity (1-2 ms) occurs for discrimination tasks. Identification of temporal order is an order of magnitude worse. When the elements of a sequence of sounds are perceived as more than one source (more than one perceptual stream), the ability to judge the order of the elements can be very poor. Perceptual grouping processes can also have dramatic effects on the perceived temporal structure of sound. Conversely, temporal structure can have a powerful influence on perceptual grouping.

Cochlea↗
PubMed1982

Noise effects in free recall with different orienting tasks.

Subjects were shown either a list of non-associated words or a list on which words could be organized into related groups. In Expt 1 either no orienting instructions were given or subjects had to rate the words for Pleasantness (semantic orienting task). The three-way interaction of noise x list type x orienting task was significant. Eighty-five dBC white noise compared with 65 dBC improved performance on the non-associated list with no orienting task and increased recall in the original sequence, but had the reverse effect with semantic orienting. With the associated list noise had no marked effects in the non-orienting condition, and improved performance in the orienting condition. It is concluded that in noise maintenance rehearsal tends to be adopted unless instructions induce an alternative strategy, and in the latter event noise reinforces use of the alternative strategy. In Expt 2, all subjects carried out a physical orienting task, rating the words for the sounds they contained. Noise aided performance on the non-associated list and impaired it on the associated list. This result is taken to be compatible with the above interpretation of noise effects.

Humans↗
PubMed2000

Localization of brief sounds: effects of level and background noise.

Listeners show systematic errors in vertical-plane localization of wide-band sounds when tested with brief-duration stimuli at high intensities, but long-duration sounds at any comfortable level do not produce such errors. Improvements in high-level sound localization associated with increased stimulus duration might result from temporal integration or from adaptation that might allow reliable processing of later portions of the stimulus. Free-field localization judgments were obtained for clicks and for 3- and 100-ms noise bursts presented at sensation levels from 30 to 55 dB. For the brief (clicks and 3-ms) stimuli, listeners showed compression of elevation judgments and increased rates and unusual patterns of front/back confusion at sensation levels higher than 40-45 dB. At lower sensation levels, brief sounds were localized accurately. The localization task was repeated using 3-ms noise burst targets in a background of spatially diffuse, wide-band noise intended to pre-adapt the system prior to the target onset. For high-level targets, the addition of background noise afforded mild release from the elevation compression effect. Finally, a train of identical, high-level, 3-ms bursts was found to be localized more accurately than a single burst. These results support the adaptation hypothesis.

Adolescent↗
PubMed2001

The influence of interaural stimulus uncertainty on binaural signal detection.

This paper investigated the influence of stimulus uncertainty in binaural detection experiments and the predictions of several binaural models for such conditions. Masked thresholds of a 500-Hz sinusoid were measured in an NrhoSpi condition for both running and frozen-noise maskers using a three interval, forced-choice (3IFC) procedure. The nominal masker correlation varied between 0.64 and 1, and the bandwidth of the masker was either 10, 100, or 1,000 Hz. The running-noise thresholds were expected to be higher than the frozen-noise thresholds because of stimulus uncertainty in the running-noise conditions. For an interaural correlation close to +1, no difference between frozen-noise and running-noise thresholds was expected for all values of the masker bandwidth. These expectations were supported by the experimental data: for interaural correlations less than 1.0, substantial differences between frozen and running-noise conditions were observed for bandwidths of 10 and 100 Hz. Two additional conditions were tested to further investigate the influence of stimulus uncertainty. In the first condition a different masker sample was chosen on each trial, but the correlation of the masker was forced to a fixed value. In the second condition one of two independent frozen-noise maskers was randomly chosen on each trial. Results from these experiments emphasized the influence of stimulus uncertainty in binaural detection tasks: if the degree of uncertainty in binaural cues was reduced, thresholds decreased towards thresholds in the conditions without any stimulus uncertainty. In the analysis of the data, stimulus uncertainty was expressed in terms of three theories of binaural processing: the interaural correlation, the EC theory, and a model based on the processing of interaural intensity differences (IIDs) and interaural time differences (ITDs). This analysis revealed that none of the theories tested could quantitatively account for the observed thresholds. In addition, it was found that, in conditions with stimulus uncertainty, predictions based on correlation differ from those based on the EC theory.

Attention↗
PubMed2001

Incorporation of loudness measures in active noise control.

An attempt has been made to use a modified version of a standard active noise control algorithm in order to take into account the unique response of the human auditory system. It has been shown in the past that decreasing the sound pressure level at a location does not guarantee a similar decrease in the perceived loudness at that location. Typically, active noise control is based on minimizing the "error signal" from a mechanical device such as a microphone, whose response is nominally flat across the frequency response range of the human ear. However, if the response of the ear can be approximated by digitally filtering the error signal before it reaches the adaptive controller, one can, in effect, minimize the more subjective loudness level, as opposed to the sound pressure level. The work reported here entails simulating active noise control based upon minimizing perceived loudness for a collection of input noise signals. A comparison of the loudness of the resulting error signal is made to the loudness of that resulting from standard sound pressure level minimization. It has been found that the effectiveness of this technique is largely dependent upon the nature of the input noise signal. Furthermore, this technique is judged to be worth considering for use with applications of active noise control where the uncontrolled noise more prominently constitutes low range audio frequencies (approximately 30 Hz-100 Hz) than medium range audio frequencies (approximately 300 Hz-600 Hz).

Algorithms↗
PubMed2001

Psychoacoustic correlates of individual noise sensitivity.

In environmental noise surveys, self-reported noise sensitivity, a stable personality trait covering attitudes toward a wide range of environmental sounds, is a major predictor of individual noise-annoyance reactions. Its relationship to basic measures of auditory functioning, however, has not been systematically explored. Therefore, in the present investigation, a sample of 61 unselected listeners was subjected to a battery of psychoacoustic procedures ranging from threshold determinations to loudness scaling tasks. No significant differences in absolute thresholds, intensity discrimination, simple auditory reaction time, or power-function exponents for loudness emerged, when the sample was split along the median into two groups of "low" vs "high" noise sensitivity on the basis of scores obtained from a psychometrically evaluated questionnaire [Zimmer and Ellermeier, Diagnostica 44, 11-20 (1998)]. Small, but systematic differences were found in verbal loudness estimates, and in ratings of the unpleasantness of natural sounds, thus suggesting that self-reported noise sensitivity captures evaluative rather than sensory aspects of auditory processing.

Adult↗