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PubMed2003

Effect of a noise modulation masker on the detection of second-order amplitude modulation.

Amplitude modulation waveforms can contain complex patterns of modulation frequency and depth that are characteristic of many biologically relevant sounds. To investigate the mechanisms involved in the processing of such patterns, we measured detection thresholds for second-order amplitude modulation (AM), a sinusoidal AM in which AM depth varies with time at frequency f(m)'. Second-order AM generates sidebands in the modulation spectrum on either side of the frequency components introduced by the first-order AM. Previous masking studies suggested that a distortion product located at f(m)' contributes to the detection of second-order AM. This hypothesis was tested by masking the putative distortion product using a noise modulation masker centred on (1) the second-order modulation frequency (f(m)'=2 Hz) and (2) the first-order modulation frequency (f(m)=16 Hz). The second-order AM was applied to a 5-kHz pure-tone carrier. Increasing the depth of a 2-Hz-wide noise modulator masker centred on 2 Hz had little effect on detection thresholds for second-order AM, but increased detection thresholds for 2-Hz first-order AM six-fold. Increasing the depth of an 8-Hz-wide noise modulator masker centred on 16 Hz increased detection thresholds for both first- and second-order AM three-fold. These results show that the detection of the second-order AM, when f(m)' is 2 Hz, is not dependent on the detection of modulation at f(m)' but is dependent on the detection of modulation components centred on f(m).

Adult↗
PubMed2004

Speech intelligibility of the callsign acquisition test in a quiet environment.

This paper reports on preliminary experiments aimed at standardizing speech intelligibility of military Callsign Acquisition Test (CAT) using average power levels of callsign items measured by the Root Mean Square (RMS) and maximum power levels of callsign items (Peak). The results obtained indicate that at a minimum sound pressure level (SPL) of 10.57 dBHL, the CAT tests were more difficult than NU-6 (Northwestern University, Auditory Test No. 6) and CID-W22 (Central Institute for the Deaf, Test W-22). At the maximum SPL values, the CAT tests reveal more intelligibility than NU-6 and CID-W22. The CAT-Peak test attained 95% intelligibility as NU-6 at 27.5 dBHL, and with CID-W22, 92.4% intelligibility at 27 dBHL. The CAT-RMS achieved 90% intelligibility when compared with NU-6, and 87% intelligibility score when compared with CID-W22; all at 24 dBHL.

Adolescent↗
PubMed1982

Temporal auditory acuity in blind and sighted subjects: a signal detection analysis.

Temporal auditory sensitivity was compared in five adventitiously blind and five normally sighted subjects in a signal-detection paradigm. Following determination of individual auditory flutter fusion (AFF) thresholds the subjects were required to make forced-choice responses between a fluttering and fused white noise under stimulus probabilities of 0.25, 0.50, and 0.75. From these data indices of sensory sensitivity (d') and response bias (Beta) were computed and compared. Analysis indicated no significant differences in auditory sensitivity between the two groups. These findings further weaken the traditional hypothesis of sensory compensation.

Adolescent↗
PubMed1985

Minimal time interval in auditory temporal resolution.

Human auditory temporal resolution was measured. Normal-hearing adults in 3 age groups (I: mn age: 24 yrs, N:55; II: mn age: 44.5 yrs, N: 25; III: mn age: 66.4 yrs, N:18) were required to indicate in which of 2 successive noise bursts of relatively low frequency (concentrated from .1-.5 kc/s) a brief temporal gap was inserted. The noise was created by passing a 100-c/s square wave through an electronic switch with virtually instantaneous rise-fall time and through a clinical audiometer to the associated earphone. The level was set at about the loudness of each S's HTL at .25 kc/s. The minimum detectable time interval (delta t) varied lawfully and significantly (p less than .001) with burst duration and with age. For all ages delta t was approximately equal to 3 msec when the burst duration was longest (85 msec), but at the shortest duration (10 msec) it rose to 17.6, 22.2, and 29.9 msec for Grps I-III, respectively. The interaction between age and duration was also significant (p less than .001). It was suggested that establishment of delta t by this or a similar procedure could offer an important parameter for evaluation of auditory function.

Adult↗
PubMed1982

Auditory brainstem responses and masking level differences from persons with brainstem lesion.

Twenty subjects with abnormal auditory brainstem responses (ABR) and diagnosed brainstem lesion or disease were studied. Normal listeners were used as controls. The objective of the project was to examine the relationship of the particular ABR patterns exhibited by these subjects to the binaural masking level differences (MLD) and transbrainstem acoustic reflex (AR) patterns yielded by the same subjects. Patients whose ABR abnormalities commenced with brainstem potentials I, II, or III had small or no MLD and absent or abnormal AR. Patients whose ABR abnormalities commenced with brainstem potentials IV or V yielded normal MLD and AR behavior. Most important, these findings suggest that MLD size is influenced by activity which also contributes importantly to the development of the early auditory brainstem potentials.

Adult↗
PubMed1988

Audiological evaluation of nonalcoholic, drug-free posttraumatic stress disorder patients.

Auditory functions of 32 Israeli soldiers with posttraumatic stress disorder (PTSD) were evaluated and compared with those of 32 matched controls without PTSD. The evaluation included peripheral auditory functions, tolerance to noise, and central auditory informational functions. Tolerance of intense auditory stimuli by PTSD patients was similar to that of controls. Significant differences were found between left and right ear central auditory functions in a subgroup of 13 PTSD subjects, but neither in other PTSD patients nor in controls. These findings are discussed in the light of previous research concerning abnormal responses to auditory stimulus in PTSD, hemispheric disconnection, alexithymia, and psychosomatic disorders.

Adult↗
PubMed2002

The neuroanatomical substrate of sound duration discrimination.

We investigated the neuroanatomical substrate of sound duration discrimination, using the same experimental design as in a previous study on sound intensity discrimination [J. Neurosci. 18 (16) (1998) 6388]. Seven normal subjects were trained to detect deviant sounds presented with a slightly longer duration than a 300 ms long standard harmonic sound, using a Go/No Go paradigm. Individual psychometric curves were assessed using a three-step psychoacoustic procedure. Subjects were then scanned while passively listening to the standard sound, and while discriminating changes in sound duration at four different performance levels (d'=1.5, 2.5, 3.5 and 4.5). Analysis of regional cerebral blood flow (rCBF) data outlined activation, during the discrimination conditions, of a right hemispheric fronto-parietal network very similar to the one previously observed for intensity discrimination, as well as additional activation in the right prefrontal cortex (Brodmann Area (BA) 10), bilateral basal ganglia and cerebellar hemispheres. These findings suggest that discrimination of sound duration, as for discrimination of sound intensity, involves two cerebral networks: a supramodal right fronto-parietal cortical network responsible for allocation of sensory attentional resources, and a network of regions such as the basal ganglia, cerebellum, and right prefrontal cortex, more specifically involved in the temporal aspects of the discrimination task.

Acoustic Stimulation↗
PubMed1991

Speech identification difficulties of hearing-impaired elderly persons: the contributions of auditory processing deficits.

This study examined the performance of four subject groups on several temporally based measures of auditory processing and several measures of speech identification. The four subjects groups were (a) young normal-hearing adults; (b)-hearing-impaired elderly subjects ranging in age from 65 to 75 years; (c) hearing-impaired elderly adults ranging in age from 76 to 86 years; and (d) young normal-hearing listeners with hearing loss simulated with a spectrally shaped masking noise adjusted to match the actual hearing loss of the two elderly groups. In addition to between-group analyses of performance on the auditory processing and speech identification tasks, correlational and regression analyses within the two groups of elderly hearing-impaired listeners were performed. The results revealed that the threshold elevation accompanying sensorineural hearing loss was the primary factor affecting the speech identification performance of the hearing-impaired elderly subjects both as groups and as individuals. However, significant increases in the proportion of speech identification score variance accounted for were obtained in the elderly subjects by including various measures of auditory processing.

Adult↗
PubMed1992

The role of spectral and temporal cues in vowel identification by listeners with impaired hearing.

This study examined the use of duration and formant frequency in the labeling of synthetic CVC stimuli forming a beet-bit continuum. Durational and F2 frequency cues to vowel identity varied systematically across stimuli. Subjects with normal hearing tended to rely primarily on F2 frequency in vowel labeling, whereas subjects with impaired hearing relied less on F2 information. This group difference was observed even for stimuli with large F2 differences, which were easily discriminated by all subjects. The effect of vowel duration on labeling was similar for both groups, with long-duration stimuli receiving more "beet" responses than short-duration stimuli across the F2 range. Psychoacoustic measures of frequency resolution and temporal resolution were poor predictors of a subject's use of formant information and duration information in labeling.

Auditory Perception↗
PubMed1983

Relations between auditory functions in impaired hearing.

Relations between auditory functions, as expressed by coefficients of correlation, were studied for a group of 22 sensorineurally hearing-impaired subjects with moderate losses. In addition to the audiogram, we measured frequency resolution, temporal resolution, and speech reception in quiet and in noise. Frequency resolution was derived from masking with comb-filtered noise and from the psychophysical tuning curve, for both paradigms in simultaneous and in nonsimultaneous masking. The critical ratio was also determined. Temporal resolution was determined with intensity-modulated noise and from backward and forward masking. All tests were performed at 1000 Hz. Correlations among tests were gathered in a matrix and subjected to a principal-components analysis. It turned out that tests on frequency resolution form a cluster, and are approximately independent of audiometric loss. Furthermore, hearing loss for speech in noise is closely allied to frequency resolution, whereas hearing loss for speech in quiet is governed by audiometric loss.

Adult↗
PubMed1979

Development of inferior colliculus response properties in C57BL/6J mouse pups.

Response properties of inferior colliculus (IC) neurons were studied in traquilized C57BL/6J mice during a period of rapid auditory system development between 12 and 17 days of age. In IC units of the youngest mice, spontaneous activity was absent, a disproportionate number of onset responses was observed, and many units were not securely driven by sound. Frequency response ranges were restricted to relatively low frequencies, sharpness of tuning was poor, and thresholds at best frequencies (BFs) were quite high. Dynamic intensity ranges were restricted, but nonmonotonic functions were observed. By 15--17 days of age, spontaneous activity was appreciable, incidences of response patterns were near adult proportions, and most units in the ventrolateral nucleus were securely driven by tones. Response ranges had expanded markedly to include high frequencies, sharpness of tuning increased, and thresholds had decreased. Dynamic intensity ranges and intensity functions were similar to those observed in adult mice.

Acoustic Stimulation↗
PubMed2001

Sensitivity to brief changes of interaural time and interaural intensity.

The purpose of this study was to measure listeners' abilities to detect brief changes in interaural temporal disparities (ITDs) or interaural intensitive disparities (IIDs) conveyed by bursts of noise (probes) temporally and symmetrically flanked by segments of diotic or uncorrelated noise. Thresholds were measured using a four-interval, two-alternative, forced-choice adaptive task and the total duration of the bursts of noise was either 20, 40, or 100 ms. Probes were temporally centered within each burst and the durations of the probes ranged from 2 to 100 ms, depending upon the duration of the (longer) total burst of noise within which they were embedded. The results indicate that, for a given total duration of noise, there is a rapid decrease in threshold ITD or threshold IID as the duration of the probe is increased so that it occupies a larger portion of the total burst of noise. Mathematical analyses revealed that both threshold ITDs and threshold IIDs could be well accounted for by assuming that the listener processes both types of binaural cues via a single, symmetric, double-exponential temporal window. Interestingly, the shapes of the temporal windows that fit the data obtained from the human listeners resemble the shapes of the temporal windows derived by Wagner [H. Wagner, J. Comp. Physiol. A 169, 281-289 (1991)], who studied the barn owl. The time constants and relative weightings yielded temporal window functions that heavily emphasize information occurring within the very temporal center of the window. This temporal window function was found to be generalizable in the sense that it also accounts for classic data reported by Grantham and Wightman [D.W. Gratham and F.L. Wightman, J. Acoust. Soc. Am. 63, 511-523 (1978)] concerning sensitivity to dynamically changing interaural disparities.

Acoustic Stimulation↗