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Noise audiometer.

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Acoustic Stimulation↗

Consonant confusions in patients with sensorineural hearing loss.

Consonant confusion matrices were obtained from 22 outpatient listeners with sensorineural hearing loss for four sets of CV and VC nonsense syllables, presented monaurally at SRT + 40 DB. Testing was typically conducted for six hours on each of two separate days. Overall performance and patterns of confusions were stable over time. Analysis of the matrices in terms of phonological features indicated that the patterns of consonant confusions varied both with degree and configuration of the subject's loss. Scaling of intersubject similarity using a pairwise multidimensional scaling analysis resulted in consistent classification of subjects according to audiometric configuration into three groups-essentially normal hearing, flat or rising audiograms, and high-frequency hearing losses.

Adult↗

Intelligibility of time-altered speech in relation to chronological aging.

The Northwestern University Auditory Test Number 6 (NU-6) measure of speech discrimination was time compressed and presented to four age groups ranging from 54 to 84 years of age. Experimental stimuli were presented at sensation levels of 24, 32, and 40 dB to an equal number of right and left ears and male and female subjects. Results indicated that intelligibility decreased as a function of increasing time compression and age and decreasing sensation level. Changes in speech intelligibility associated with the aging process appear to be closely allied to changes in the temporal resolving power of the central auditory processing system.

Adult↗

Effects of stimulus frequency and intensity on the middle componenets of the averaged auditory eletroencephalic response.

Middle components (latency 8-50 msec) of the averaged auditory electroencephalic response (AAER), evoked by brief duration tone bursts, were recorded from 11 normal-hearing subjects. Latency and amplitude measurements were made on five peaks (Na, Pa, Nb, Pb, and Nc) of the AAER waveforms recorded for 27 experimental conditions: three conditions of stimulus frequency (250, 1000, and 4000 Hz) at each of nine conditions of signal intensity (a no-stimulus control and 10, 20, 30, 40, 50, 60, 70, and 80 dB fe: group thresholds). Latency for each peak decreased with increased stimulus frequency, and it tended to decrease slightly with increases in stimulus intensity. Amplitude input-output characteristics varied with stimulus frequency and response peak. In general, the most linear input-output characteristics occurred for the early peaks and high stimulus frequencies. Characteristics for later peaks and lower frequencies tended to asymptote at moderate stimulus intensities. Between-subject variability was not much greater than within-subject variability for the single event auditory evoked potential (AEP). The variance of the AEP, however, was nearly as great (as much as two-thirds) as the variance of the background EEG, despite the large difference between AEP and background EEG amplitude.

Acoustic Stimulation↗

The acoustic reflex and temporary threshold shift: temporal characteristics.

One ear of each of seven normal-hearing subjects was exposed to a continuous 1000-Hz tone at 110 dB SPL for three minutes. During exposure, a broad-band noise at 100 dB SPL was presented to the contralateral ear. The noise was either continuous or pulsed. Four pulsed conditions employed repetition periods of 360, 180, 90, or 9 msec with a 50% duty cycle. A control condition in which no noise was presented was also included. Temporary threshold shift was measured at selected postexposure times at the frequency one-half octave above the exposure frequency. TTS2 was greatest for the control condition and least for the 360- and 180-msec conditions. Results are discussed in relation to the dynamics of the acoustic reflex, particularly reflex relaxation, reflex adaptation, and reflex temporal summation.

Acoustic Stimulation↗

Auditory discrimination of voiceless fricatives in children.

Auditory discrimination of the voiceless fricatives magnitude of theta f integral of s was studied in 200 subjects between the ages of four and six and a half years. In the test task the subject was asked to remember one of the sounds and then to indicate each time this sound was presented. Two types of errors were analyzed. An error of omission was a failure to identify the remembered sound, and this type of error did not change with age. An error of commission, a failure to discriminate between the remembered sound and one of the other voiceless fricatives, decreased with age. The results are interpreted as support for a theory of the development of auditory perception of speech in which discrimination of some properties in speech, such as relatively weak spectral cues and second formant transitions, have to be learned by a child.

Age Factors↗

Detection of tones in band-reject noise.

Three experiments were conducted to investigate the detectability of tonal signals simultaneously presented with computer-generated, long duration (.5 sec), band-reject maskers. In Experiment 1, detectability of a tone of 500, 1000, or 2000 Hz presented at 50 dB SPL was measured as a function of the width of a spectral "notch" symmetrically placed around the tone. A narrow notch resulted in decreased detectability relative to the wide band (zero-notch width) control condition. Further increases in notch width resulted in increased detectability until subjects approached errorless performance. In Experiment 2, psychometric functions were obtained for a 1000-Hz tone presented in four notch-noise conditions. The slopes of the psychometric functions were consistently steeper in the band-reject conditions relative to the zero notch-width condition. These slope differences result in relationships between threshold and notch width that depend upon the region of the psychometric function from which the threshold estimates are obtained. In Experiment 3, the decrease in performance associated with the notch was found to increase in proportion to notch depth. The data suggest that spectral edges placed in the immediate vicinity of a tone reduce the detectability of the tonal signal. This "edge effect" is discussed in relation to two-tone inhibition that has been observed in the auditory nerve.

Acoustic Stimulation↗

Tone-on-tone masking in subjects with normal hearing and with sensorineural hearing loss.

Quiet and masked thresholds were obtained from 5 subjects with normal hearing and 31 subjects with sensorineural hearing loss. Maskers were pure tones varying in frequency and intensity. The hearing-impaired subjects showed an abnormal spread of masking when masking was measured in terms of masked threshold. The abnormal spread of masking seems to be related to both the hearing threshold of the masker and the quiet threshold of the test signal. The notch due to detection of combination tones found on the high-frequency slope of masked audiograms of normal subjects (obscuring the actual extent to which the signal is masked) tends to accentuate the apparent abnormal upward spread of masking in the hearing-impaired subjects. The abnormal spread in the latter case is real, but comparison with the normal case must take the notch into account.

Acoustic Stimulation↗

Temporal integration of tone glides by children with auditory-memory and reading problems.

Temporal auditory integration for short-duration, frequency-varying signals was examined in children with deficits in auditory memory and reading. Signals were similar to those previously used: a fixed-frequency tone, a tone glide rising in frequency, and a tone glide falling in frequency. No significant differences were found between the Experimental and Control groups' thresholds as a function of signal class (i.e., fixed-frequency or tone glide) or duration. In addition, a significant asymmetry in the thresholds of short-duration rising and falling tone glides was found for both groups. Falling tone glides were detected at higher intensities than were rising tone glides. Data from this study indicated this particular group of children with auditory memory and reading problems was able to detect simple and complex short-duration signals in a manner similar to normal children.

Acoustic Stimulation↗