PESTI: A procedure for estimating individual thresholds in infant listeners

An adaptive procedure for rapid estimation of adult thresholds (PEST: Parameter Estimation by Sequential Testing; Taylor & Creelman, 1967) was modified and applied to the estimation of auditory thresholds in 6-month-old infants (PESTI). This procedure yielded similar absolute thresholds to those obtained in previous research with the method of constant stimuli. Advantages of the present procedure are outlined.     

Detection and discrimination thresholds for auditory periodicity

Complex periodic auditory signals, produced by the Guttman-Julesz procedure of repeating segments of random noise, were employed to address the low region of auditory periodicity. Periodicity detection and discrimination tasks were examined with a common experimental procedure and a common measure of thresholds. Typically, detection and discrimination performance suffer at extremely low periodicities, presumably because of the extremely close spacing of harmonics throughout the auditory spectrum. Interaural phase effects are extremely weak for these signals, being largely confined to threshold-detection tasks. Despite qualitative phenomenological differences for different periodicity regions, detection and discrimination functions show no sharp discontinuities over a wide range of periodicities.     

Frequency selectivity for hearing-impaired and broadband-noise-masked normal listeners

When evaluating frequency selectivity, it is difficult to determine if the deviation from normal performance observed for hearing-impaired listeners reflects abnormal cochlear function or normal, level-dependent changes in frequency selectivity. This experiment was designed to investigate the dependence of frequency-selectivity measures on threshold and signal level. Auditory-filter characteristics, critical ratios, forward-masked psychophysical tuning curves, and narrowband-noise masking patterns were obtained from normal-hearing listeners in quiet and in the presence of broadband noise at five levels. These findings were then compared to previously obtained frequency-selectivity measurements for subjects with mild-to-moderate sensorineural hearing loss whose absolute thresholds are comparable to the normal-hearing listeners' masked thresholds. The results suggest that frequency selectivity deterioriates as threshold increases for all subjects. However, the poor frequency selectivity exhibited by hearing-impaired listeners may not be explained entirely by the effects of threshold and signal level. Nevertheless, because frequency selectivity is poorer in the normal auditory system at higher stimulus levels, the deviation from normal performance observed for hearing-impaired listeners may not be as large as previously suggested.     

Effect of simultaneous auditory stimulation on vibrotactile thresholds

Vibrotactile thresholds were determined at 250 and 400 Hz in the presence of (1) the sounds emitted by the vibrator, (2) continuous tonal or narrow-band masking noise, or (3) a pulsed tone synchronized with the vibrator signal. The measure of a cross-modality effect was the threshold shift occurring between each condition and the control condition, in which earmuff silencers eliminated the vibrator sounds. Continuous tones or noise had no effect upon vibrotactile thresholds. However, auditory signals synchronized with the vibrator signals did significantly elevate vibrotactile thresholds.     

A forced-choice adaptive procedure for measuring auditory thresholds in children

A modification of the two-down/one-up tracking procedure was used to estimate thresholds of audibility in 46 children (ages 3 to 6 years) and 10 adults. A two-alternative forced-choice version (26 children, 5 adults) of this method was successful in estimating thresholds of audibility in 5-year-olds, but not in 3- and 4-year-olds. A single-interval version of the procedure was successful in estimating thresholds of audibility for all the children. Measures from the children of between- and within-subjects variability, psychometric functions, and response bias all indicate that the procedure enables one to estimate thresholds that are in close agreement with those obtained from adults and with results of other investigators.     

A comparison of chinchilla auditory evoked response and behavioral response thresholds

The auditory sensitivity of the chinchilla was measured by both a behavioral and auditory evoked-response (AER) procedure. There was no significant difference in either the waveform or the threshold of the AER recorded over the tentorium from awake and anesthetized chinchillas. The chinchilla threshold for pure tones appears to be more sensitive when measured by the behavioral technique than by the AER method. Both the AER and behavioral response of three chinchillas exposed to a 105 dB SPL octave band of noise centered at 2 KHz for 3 h shifted markedly after the exposure. However, the difference between the AER and behavioral response threshold was reduced or absent. During the process of recovery the difference between the two responses begins to reappear.     

Strain differences in auditory thresholds in the canary (Serinus canarius)

Canaries (Serinus canarius) of the Belgian waterslager strain from two different colonies were trained with operant techniques for audiometric testing. For both young and old birds, absolute thresholds in the middle- to high-frequency region of the audiogram were between 30 and 40 dB (SPL) higher than those of other song birds, including canaries of other strains. Thus the Belgian waterslager canary, selectively bred for loud, low-pitched song, has also developed poor high-frequency hearing.     

The effect of warning interval on the electric phosphene and auditory thresholds

Using different warning signals and threshold stimuli, the thresholds, as determined by a method of limits, were found to rise monotonically as the interval between warning signal and threshold stimulus increased from I to 9 sec. It was found that the variability of the threshold did not increase as the threshold increased. Similar results were obtained for phosphene and auditory thresholds and with visual and auditory warnings; therefore the effect was considered to be central. Motokawa's finding of a minimum in the phosphene threshold 2 sec. after a flash of white light was not repeated. The rise in threshold was not obtained when the warning intervals were randomized and so seemed to depend on the use of fixed warning intervals. A model was developed relating threshold level to accuracy of anticipation of the end of the warning interval.     

Effects of rate and word boundary ambiguity on recall by normal and impaired listeners

Twenty normal-hearing and 20 hearing-impaired persons heard experimental sentences that included two syllables with an ambiguous word boundary and control sentences that did not include an ambiguous word boundary. The sentences were produced at two rates. Difficulty in generating a meaning for the ambiguous word boundary that made sense within the sentence appeared to reduce recall. For the normal-hearing persons, the difficulty with the ambiguous word boundary reduced recall of experimental sentence words when the speech was fast but not when it was slow. For the hearing-impaired persons, the difficulty reduced the recall of the experimental sentence words when the speech was slow but not when it was fast. Two weeks later, the same listeners heard a set of two syllables having ambiguous word boundaries that were isolated from their sentences. Varying speed of speaking affected the segmentation of the two syllables by the normal-hearing more than it affected the segmentation by the hearing-impaired.This work was supported by NINDS Grants No. NS10468 and 05362.     

Effect of auditory masking on lingual vibrotactile thresholds and magnitude estimation scaling responses

Auditory masking has become a frequently employed part of the procedure used in vibrotactile research. Research investigating the effect of auditory masking on lingual vibrotactile thresholds of sensitivity has shown that there is little difference between lingual vibrotactile thresholds under masking and no masking conditions. The purpose of the present study was to extend the investigation of the effect of auditory masking to include lingual vibrotactile suprathreshold scaling responses. 20 young adult subjects of mean age 19 yr. completed lingual vibrotactile-threshold and magnitude-estimation scaling tasks under conditions of bilateral auditory masking and no masking. Similar lingual vibrotactile-threshold values and magnitude-estimation power-function exponents for the conditions of masking and no masking were noted.     

Hemispheric lateralization of bilaterally presented homologous visual and auditory stimuli in normal adults, normal children, and children with central auditory dysfunction

Two experiments were conducted to examine the performance of normal adults, normal children, and children diagnosed with central auditory dysfunction presumed to involve the interhemispheric pathways on a dichotic digits test in common clinical use for the diagnosis of central auditory processing disorder (CAPD) and its corresponding visual analog. Results of the first experiment revealed a significant right ear advantage (REA) for the dichotic listening task and a left-visual-field advantage (LVFA) for the corresponding visual analog in normal adults and children. In the second experiment, results revealed a significantly larger REA in the children with CAPD as compared to the normal children. Results also revealed a reversed cerebral asymmetry (RVFA) for the children with CAPD on the visual task. Significant cross-modal correlations suggest that the two tasks may reflect, at least in part, similar interhemispheric processing mechanisms in children. Findings are discussed in relation to differential diagnosis and modality-specificity of CAPD.     

Hearing in passerine and psittacine birds: a comparative study of absolute and masked auditory thresholds

Operant conditioning and a psychophysical tracking procedure were used to measure auditory thresholds for pure tones in quiet and in noise for seven species of small birds--the budgerigar, canary, cockatiel, European starling, song sparrow, swamp sparrow, and the zebra finch. Audibility curves are roughly similar among the seven birds, with the maximum sensitivity between 2 and 5 kHz and poorer sensitivity outside this narrow region. Critical ratios (signal-to-noise ratio at masked threshold) were calculated from pure-tone thresholds in noise. Except for the budgerigar, the critical ratio functions of all birds increase at the rate of 3 dB/octave. This pattern is typical of that observed in most vertebrates. Critical ratios in the budgerigar, on the other hand, decrease gradually from 0.5 kHz to 2.8 kHz and increase dramatically above 2.8 kHz. The present research demonstrates that the critical ratio function for the budgerigar is not only different from other vertebrates but also different from other birds.     

Speech disfluencies under normal and delayed auditory feedback conditions

20 male and 20 female adults, matched by age, read under conditions of normal and 113-, 152-, 200-, 253-, 307-, and 347-msec. delayed auditory feedback. Disfluency counts were correlated with delayed auditory feedback reactions which were changes in disfluencies under delay conditions. Pearson product-moment and Spearman's rbos were negative and significant for delay times of 113, 153, 200, and 253 msec. The Pearson product-moment correlation for 307 msec. was also negative and significant. Two groups of 11 adults were selected from the original sample on the basis of high and low initial disfluency counts. Their reactions to delayed auditory feedback were compared, using a 2-way analysis of variance with repeated measures (groups X delay times). Both main effects were significant but not their interaction.     

A comparison of two flash and two click thresholds in schizophrenic and normal subjects

The thresholds of fusion of paired flashes and paired clicks were compared. It was found that schizophrenics tended to show relatively higher click thresholds than normal subjects and in the most deteriorated schizophrenics two click thresholds tended to be higher than two flash thresholds.