Duration discrimination and subjective duration for ramped and damped sounds.

The perception of stimuli with ramped envelopes (gradual attack and abrupt decay) and damped envelopes (abrupt attack and gradual decay) was studied in subjective and objective tasks. Magnitude estimation (ME) of perceived duration was measured for broadband noise, 1.0-kHz, and 8.0-kHz tones for durations between 10 and 200 ms. Damped sounds were judged to be shorter than ramped sounds. Matching experiments between sounds with ramped, damped, and rectangular envelopes also showed that damped sounds are perceived to be shorter than ramped sounds, and, additionally, the reason for the effect is a result of the damped sound being judged shorter than a rectangular-gated sound rather than the ramped sound being judged longer than a rectangular-gated sound. These matching studies also demonstrate that the size of the effect is larger for tones (factor of 2.0) than for broadband noise (factor of 1.5). There are two plausible explanations for the finding that damped sounds are judged to be shorter than ramped or rectangular-gated sounds: (1) the abrupt offset at a high level of the ramped sound (or a rectangular-gated sound) results in a persistence of perception (forward masking) that is considered in judgments of the subjective duration; and (2) listeners may ignore a portion of the decay of a damped sound because they consider it an "echo" [Stecker and Hafter, J. Acoust. Soc. Am. 107, 3358-3368 (2000)]. In another experiment, duration discrimination for broadband noise with ramped, damped, and rectangular envelopes was studied as a function of duration (10 to 100 ms) to determine if differences in perceived duration are associated with the size of measured Weber fractions. A forced-choice adaptive procedure was used. Duration discrimination was poorer for noise with ramped envelopes than for noise with damped or rectangular envelopes. This result is inconsistent with differences in perceived duration and no explanation was readily apparent.

Safety and clinical performance of acoustic reflex tests.

OBJECTIVE: Safety and effectiveness of acoustic reflex tests are important issues because these tests are widely applied to screen for retrocochlear pathology. Previous studies have reported moderately high sensitivity and specificity for detection of acoustic neuroma. However, there have been reports of possible iatrogenic hearing loss resulting from acoustic reflex threshold (ART) and decay (ARD) tests. This study assessed safety and clinical performance of ART tests for detection of acoustic neuroma. DESIGN: We report a case in which ARD testing resulted in a significant bilateral permanent threshold shift. This case was the impetus for us to investigate the clinical utility of ART and ARD tests. We analyzed sensitivity and specificity of ART, as well as asymmetry in pure-tone thresholds (PTT) for detection of acoustic neuroma in 56 tumor and 108 non-tumor ears. RESULTS AND CONCLUSIONS: Sensitivity and specificity were higher for PTT asymmetry than for ART. Ipsilateral ART at 1000 Hz had poor sensitivity and specificity for detection of acoustic neuroma, and involves some potential risk to residual hearing for presentation levels higher than 115 dB SPL. Approximately half of the acoustic neuroma group had ipsilateral ARTs that would require administration of ARD tests at levels exceeding 115 dB SPL. Therefore, we conclude that PTT asymmetry is a more effective test for detection of acoustic neuroma, and involves no risk to residual hearing. Future studies of contralateral reflex threshold and ARD in combination with PTT asymmetry are recommended.

The peaked audiometric configuration in Meniere's disease: disease related?

A retrospective analysis of audiograms was completed for persons from 3 different patient groups. These 3 groups were (1) persons with unilateral Meniere's disease, (2) persons with unilateral acoustic tumor, and (3) persons from the general clinical population of an audiology clinic in a major medical center. As Paparella, McDermott, Luiz, and de Sousa (1982) also report, the most common audiometric configuration in the Meniere's disease group was peaked, a condition in which poorer hearing is reported in the low and high frequencies, and an island of better hearing sensitivity occurs at either 1.0 or 2.0 kHz. Some of the peaked audiograms from persons in our Meniere's disease group could be a result of a low-frequency hearing loss caused by Meniere's disease combined with a high-frequency hearing loss due to aging or other environmental factors. However, 27% (13/48) of the peaked audiograms in ears with Meniere's disease were found in persons with no hearing loss in the high frequencies of their nondiseased ear. Thus, the peaked audiometric configuration is associated with Meniere's disease, as suggested by research results from animals with experimentally induced endolymphatic hydrops. Peaked audiometric configurations were also observed in roughly 9% of the general clinical population and in 12.5% of ears of persons with acoustic tumors. A rule--based on the audiometric configurations that maximized identification of patients with Meniere's disease--using the general clinical population as a control did not fare as well when the tumor group was used as a control. This finding provides further evidence that peaked audiograms, although common to Meniere's disease, are not pathognomonic of this disease. Furthermore, these results indicate that the diagnosis of Meniere's disease from audiometric profiles is risky, at best.

Masker laterality and cueing in forward-masked intensity discrimination.

Forward-masked intensity discrimination was measured as a function of level in experiments designed to reveal insights into the mechanism(s) underlying the midlevel elevation of the Weber fraction. The standard and maskers were 1.0-kHz tones that were separated by 100 ms. Performance was measured for listeners with normal hearing using an adaptive procedure. In experiment 1, intensity discrimination was measured in the presence of an ipsilateral masker (80 dB SPL), a contralateral masker (93 dB SPL), and a binaural (dichotic) masker produced by combining the ipsilateral and contralateral maskers. Listeners perceived only the contralateral masker in the binaural-masker condition. The contralateral masker produced a small midlevel elevation of the Weber fraction. The ipsilateral masker and the binaural masker produced a large, midlevel elevation of the Weber fraction. Experiment 2 found that a two-tone masker resulted in a reduction (improvement) in the Weber fraction for some conditions, but the midlevel elevation remained for all subjects in this cue-tone condition. Experiment 3 demonstrated that cross talk could not account for all of the masking observed with contralateral maskers. Taken together, the results suggest that a single complex mechanism or multiple mechanisms may be responsible for the masking seen in these experiments. On the basis of the cueing results, it is concluded that a portion of the masking is due to cognitive factors; however, a sensory mechanism cannot be ruled out for the remaining portion, based on the results of these experiments. Finally, a small but significant amount of masking due to contralateral maskers places the mechanism for this outcome central to the cochlear nucleus.

Basilar membrane nonlinearity and loudness.

Loudness matching functions for tones for persons with one shifted-threshold ear (hearing loss and noise-shifted thresholds) and one ear within normal limits were used to derive the presumed basilar membrane (BM) input-output (I/O) function in a normal ear. The comparison was made by assuming that the BM I/O function for the ear with the cochlear threshold shift has a slope of one (a linearized cochlea). The function for the normal ear was derived from the loudness matching function based on this assumption. Comparisons were made for archival basilar membrane data [M. A. Ruggero, N. C. Rich, A. Recio, S. S. Narayan, and L. Robles, J. Acoust. Soc. Am. 101, 2151-2163 (1997)] for chinchilla and archival loudness matches for long-duration tones for persons with various degrees of cochlear hearing loss [F. Miskolczy-Fodor, J. Acoust Soc. Am. 32, 486-492 (1960)]. Comparisons were made also between BM I/O functions and ones derived from loudness matches for persons with unilateral hearing loss simulated by broadband noise. The results show a close resemblance between the basilar membrane I/O function and the function derived from loudness matches for long-duration tones, even though the comparison was between human and chinchilla data. As the degree of threshold shift increases from 40 to 80 dB, the derived BM I/O functions become shallower, with slopes for losses of 60 dB or more falling in the range of values reported for physiological data. Additional measures with short-duration tones in noise show that the slope of the loudness function and the slope of the derived basilar membrane I/O function are associated with the behavioral threshold for the tone. The results for long-duration tones suggest a correspondence between BM displacement and loudness perception in cases of recruitment, but the relation between the degree of loss and the amount of BM compression and the relation between signal duration and compression suggests that other factors, such as the neural population response, may play a role.

Forward-masked intensity discrimination: duration effects and spectral effects.

Three experiments were completed to examine the effect of masker duration and spectrum on forward-masked intensity discrimination. Four listeners participated in each experiment. Intensity discrimination was measured in quiet and in the presence of forward maskers using adaptive forced-choice procedures. The standard duration was either short (10 ms) or long (250 ms) in experiment 1 and short (10 ms) in experiment 2. The standard always occurred 100 ms after the offset of the masker. In the first experiment employing 1.0-kHz maskers and standards, a short duration masker (10 ms) produced more masking than a long duration masker (250 ms). A mid-level elevation of the Weber fraction was observed for all conditions. To ensure that the results of experiment 1 were not influenced by off-frequency listening, the second experiment employed a broadband noise masker. As before, a short duration (10 ms) masker produced more masking than a long duration masker (100 ms) and a mid-level elevation of Weber fractions was observed. This outcome is inconsistent with a peripheral sensory effect for which an increase in masker duration should result in a greater amount of adaptation, and, as a consequence more masking. A third experiment employing a broadband noise masker and standard showed the greatest amount of masking for low-level standards, but only when the duration of the masker and standard was short. This result is similar to one seen for a single listener in the first experiment for short duration tonal maskers and standards. For this listener, a second tone presented at 4.133 kHz presented simultaneously with the 1.0 kHz masker reduced significantly the amount of masking for low-level standards, but the mid-level elevation of the Weber fraction remained. Taken together, these results suggest that perceptual similarity plays a role in forward-masked intensity discrimination but does not account entirely for the mid-level elevation of the Weber fraction.

Identification of pseudohypacusis using speech recognition thresholds.

OBJECTIVE: To determine the extent to which procedural variations affect pure-tone average-spondee threshold (PTA-SRT) agreement in pseudohypacusis, to propose a theoretical framework to account for threshold differences due to procedural variations, and to devise an effective screening test for identification of pseudohypacusis. DESIGN: The subjects were normally hearing listeners who feigned a hearing loss. One experimental group received an ascending pure-tone (PT) technique combined with an ascending SRT procedure. A second experimental group received an ascending PT technique paired with a descending SRT procedure. A third experimental group received an ascending SRT procedure paired with a descending PT procedure. RESULTS: The group mean difference between the three-frequency PTA and the SRT was 10.6, 2.3, and 41.6 dB for the first, second, and third experimental groups, respectively. Comparison SRTs and PTAs from cooperative patients with hearing loss showed that a two-frequency PTA yielded a more effective test for pseudohypacusis than did a three-frequency PTA. CONCLUSIONS: The procedural differences noted in this study are consistent with a loudness bias. It is recommended that clinicians employ an ascending procedure to measure SRTs and a descending procedure to measure PT thresholds to maximize the effectiveness of a screening test for pseudohypacusis based on PTA-SRT differences.

Evaluating hearing threshold differences between ears as a screen for acoustic neuroma.

Differences in pure tone thresholds between ears were evaluated at two different patient care facilities to determine this measure's value as a screen for acoustic neuroma. We evaluated the audiograms of tumor and nontumor groups to estimate the true positive rates and false positive rates for several decision rules. Threshold differences were found to be a more effective diagnostic tool for females than for males. However, even for the most effective rules, the efficiency of this test alone is mediocre, which indicates that hearing threshold differences between ears must be combined with other criteria for a cost-effective approach to acoustic neuroma identification. Furthermore, tumor size was not predicted by the amount of threshold asymmetry between ears, which suggests that some large, potentially life-threatening tumors may be missed if pure tone threshold differences are the sole criterion for referral for additional tests.

Intensity resolution and loudness in broadband noise.

Intensity resolution and loudness matching behavior for pure tones was studied in quiet and in two levels of noise (15 and 40 dB spectrum level) to test the predictions of several models for relating these phenomena. Five normally hearing listeners participated. The Weber functions in noise were elevated compared to the ones in quiet when comparisons were made at equal sound-pressure levels (SPLs). Loudness matching functions (dB SPL in quiet versus dB SPL in noise) showed a slope greater than unity. Modified power functions with threshold corrections were fitted to the matching data to estimate the loudness function exponent. The best-fitting loudness exponent for individual and group data (range = 0.24-0.35) was in the range of values typically found using magnitude estimation procedures for the loudness equation yielding the best fit. Three models for predicting Weber functions from loudness were evaluated with this loudness representation. One of these models, the subjective analog to Weber's law, yielded results inconsistent with the observed data. The other models, McGill and Goldberg's [J. Acoust. Soc. Am. 44, 576-581 (1968)] neural counting model and the proportional-jnd theory, predicted Weber functions that are consistent with the observed data if the variance of the decision variable is assumed to change in quiet and noise backgrounds. The proportional-jnd theory has such a change built into the model, but the underlying physiological mechanisms responsible for its success are unknown.

Intensity resolution and loudness in high-pass noise.

Intensity resolution and loudness growth for a 1000-Hz tone were studied in the presence of high-pass noise (cutoff: 1800 Hz). Intensity resolution was measured for gated and continuous standards using a three-interval forced-choice (3-IFC) adaptive procedure. Loudness matches were obtained using an adaptive, alternate binaural loudness balance procedure. Three subjects listened in three conditions (1) quiet; (2) high-pass noise with a spectrum level of 32 dB SPL; and (3) high-pass noise with a spectrum level of 42 dB SPL. Noise levels were selected so that detection thresholds were minimally affected at the test frequency; however, for frequencies in the noise passband, thresholds were shifted to either 50 or 60 dB SPL, depending on the spectrum level of the noise. On average, loudness growth and intensity resolution were unaltered by the presence of the noise for tonal levels below 40 dB SPL; above 40 dB SPL the following was generally true: (1) intensity resolution for gated standards was well described by Weber's law except at the highest levels where the Weber fraction decreased; (2) intensity resolution for continuous standards showed a "near-miss" to Weber's law, but just-noticeable differences (jnd's) were slightly larger than those in quiet for the same SPL; (3) loudness was reduced. A comparison of jnd's for equally loud tones showed that loudness is less dependent on excitation spread than the jnd. That is, jnd's in the threshold-shifted ear were larger than the ones in quiet when the comparison was made for tones judged to be equally loud.(ABSTRACT TRUNCATED AT 250 WORDS)

Attending to auditory filters that were not stimulated directly.

The effectiveness of two types of tonal cues for reducing frequency uncertainty was studied in a tonal detection-in-noise task. Signals varied at random from trial to trial over the range 750-3000 Hz. The three conditions included: (1) maximum uncertainty in which there were no cues; (2) minimal uncertainty in which "iconic cues" were identical to the signal to be detected; and (3) partial uncertainty in which "relative cues" were set to 2/3 of the signal frequency, i.e., at the musical 5th. Results show that relative cues and iconic cues were both effective in reducing uncertainty compared to the no-cue condition, but that performance with relative cues was poorer than with iconic cues by 1.4 dB. In addition, a modified probe-signal method was used to estimate the widths of the subjective listening bands. Application of a model of the auditory filter [R. Patterson and B. C. J. Moore, Frequency Selectivity in Hearing, edited by B. C. J. Moore (Academic, New York, 1986)] to these data showed that the subjective listening bands used with iconic cues were similar in width to typical measures of the critical band but that the bands used with relative cues were wider by a factor of roughly 1.6.

A cognitive influence on the loudness of tones that change continuously in level.

The loudness of tones that change continuously in level over time was studied using magnitude estimation and a delayed loudness-balance procedure. In the magnitude estimation task, subjects estimated the loudness of continuous and intermittent 1000-Hz tones that either increased or decreased continuously in level over roughly 3 min. Two stimulus ranges were used: 30 to 70 and 50 to 90 dB SPL. For the low-level conditions, the results are essentially identical to those of Canévet and Scharf [J. Acoust. Soc. Am. 88, 2136-2142 (1990)], who ran similar conditions. Tones that increased in level changed in loudness as a function of SPL at a slower rate than tones that decreased in level. For the high-level conditions, the same result was obtained, but the magnitude of the difference among conditions is smaller. A delayed loudness-matching procedure was used to measure the physical magnitude corresponding to loudness differences among a subset of the conditions. Judged equal-loudness levels showed a sharp decline in loudness for conditions with tones that decreased continuously in level, but the magnitude of the reduction was less than that interpolated from magnitude estimates for identical stimuli. The source of the difference is unclear. To explore the role of cognitive influences, subjects' attention was diverted by a video word-identification task during the period of adaptation. For this task, the loudness decline was reduced for loudness balances and magnitude estimations compared to conditions where attention was concentrated on the adapting stimulus. In another magnitude-estimation task, the loudness decline for monaural stimulation was found to occur only in the "adapted" ear.(ABSTRACT TRUNCATED AT 250 WORDS)

Listening bandwidths and frequency uncertainty in pure-tone signal detection.

The effect of frequency uncertainty on the detection of tonal signals in noise was studied using a modified probe-signal method. Widths of the listening bands used during detection were measured directly, allowing for an analysis that separates the effects of having to monitor multiple independent bands from those due to limited frequency resolution. Uncertainty was varied by beginning each trial with a cue consisting of one, two, or four randomly chosen, simultaneously presented tones. An expected signal, whose frequency matched one of the components in a cue, was presented on a majority of trials. However, on remaining trials, the signal was a probe, which meant that its frequency differed from one of the components in the cue by a constant ratio. Performance as measured in percent correct declined for probes at increasingly distant ratios from the expected values. The results were converted to dB using individual psychometric functions for expected signals and listening bands were fitted using the rounded exponential filter of Patterson et al. [J. Acoust. Soc. Am. 72, 1788-1803 (1982)]. The obtained bandwidths are comparable to those reported using notched-noise maskers, but there is a small but consistent increase in bandwidth with increased numbers of components in the cues. The primary results is that the effects due to uncertainty are well described by a 1-of-M orthogonal band model, which takes into consideration limitations of the detector, including the widths of the listening bands.

A comparison of psychometric functions for detection in normal-hearing and hearing-impaired listeners.

Psychometric functions (PFD) for the detection of pure tones were obtained with a two-interval forced-choice procedure from a group of listeners with normal hearing and a group of listeners with sensorineural impairments of presumed cochlear origin. Five PFDs were obtained for each group at each of the four test frequencies (500, 2000, 4000, and 8000 Hz). The slopes of PFDs were abnormally steep in some of the hearing-impaired listeners, but were statistically significant only at 2000 Hz.

Two-, three-, and four-interval forced-choice staircase procedures: estimator bias and efficiency.

Threshold estimates for multiple-interval forced-choice staircase procedures were studied using computer simulations. A sigmoidal psychometric function shape governed the hypothetical subject's responses in the simulations. Parameters varied included the number of trials, the step size for stimulus level change, and decision rules that targeted 70.7% and 79.4% correct performance. Each threshold estimate was calculated by averaging the stimulus levels at which a reversal a stimulus level direction occurred. The results of the simulations suggest that, as the number of alternatives is increased from 2 to 4, the variability of repeated threshold estimates decreases or remains constant, and the accuracy of the estimator, in most cases, improves. A subset of the simulations was compared with data obtained in a detection-in-noise task. The behavioral data were consistent with the simulation results. Two major conclusions were reached. First, 3- and 4-interval forced-choice (IFC) procedures are more efficient than a 2IFC procedure with a decision rule that targets 70.7% correct performance even when the additional time required to complete 3- and 4IFC trials is considered. Second, the accuracy of 2IFC procedures can be improved by fitting the trial history of a staircase run using probit analysis.

Methodological variables affecting phonational frequency range in adults.

This study examined the effects of selected elicitation variables on phonational frequency (Fo) range in normal adults. Twenty men and 20 women responded to five audiotaped tone conditions: (a) discrete steps, (b) slow steps, (c) fast steps, (d) slow glissando, and (e) fast glissando. These stimuli were devised to elicit each person's maximal and minimal Fo. All elicitation conditions evoked a significantly higher maximal Fo and a significantly larger Fo range (in both hertz and semitones) than did the discrete-steps condition. Fast steps produced a significantly higher minimal Fo than did fast glissando. Both slow glissando and fast glissando yielded a significantly larger Fo range in semitones than did fast steps. Finally, the women demonstrated a significantly larger Fo range (in hertz but not semitones) than did the men.

Factors influencing fundamental frequency range estimates in children.

Selected elicitation conditions were manipulated to determine their effect on fundamental frequency (Fo) range estimates in children. Forty normal children each responded to five autiotaped tone conditions: (a) discrete steps, (b) slow steps, (c) fast steps, (d) slow glissando, and (e) fast glissando. These tonal stimuli were devised to elicit each child's maximal and minimal Fo. The traditional discrete-steps condition was associated with a lower maximal Fo, higher minimal Fo, and a more restricted Fo range than all other conditions.

A method for relating loudness-matching and intensity-discrimination data.

A method that allows direct comparisons between pure-tone loudness-matching and intensity-discrimination data in normal and hearing-impaired listeners is described. This method makes a minimal number of assumptions about the relations between loudness perception and intensity-discrimination performance. Loudness is considered to be related to overall, perceived stimulus magnitude and intensity-discrimination performance is considered to reflect the accuracy with which a loudness judgment can be made. Because pure-tone intensity-discrimination performance varies as a function of stimulus level in normal ears, the standard level required to produce a particular difference limen in an impaired ear can be inferred from normal-ear intensity-discrimination data. Thus, plotting standard levels yielding normal difference limens as a function of standard levels yielding the equivalent sized difference limens from a threshold-shifted ear produces a function directly comparable to loudness recruitment functions. If loudness-growth and intensity-difference limens were tightly coupled in threshold-shifted ears, then stimuli that yield equal size difference limens would be equally loud. This relation was tested by obtaining loudness-matching and intensity-discrimination data from normal-hearing listeners with thresholds shifted by a wideband noise and hearing-impaired listeners with cochlear-type hearing losses. The results from these listeners show similarities between the traditional loudness-recruitment functions and "intensity-recruitment" functions derived from the assumed relation between the two measures. The primary difference between the functions is at low and moderate sensation levels where loudness grows at a more rapid rate than the difference limen.

The relations among critical ratios, critical bands, and intensity difference limens in man.

Band-narrowing estimates of the critical bandwidth (CB) are consistently larger than critical-ratio (CR) estimates for the same signal frequency. Bilger [in Hearing and Davis: Essays Honoring Hallowell Davis, edited by S.K. Hirsh et al. (Washington U.P., St. Louis, 1976), p. 191] proposed that this difference could be accounted for by reference to intensity-discrimination performance [CR(Hz)/CB(Hz) = delta I/I]. To test this hypothesis, band-narrowing, critical-ratio, and intensity-discrimination data were collected for four normally hearing, well-trained listeners. Signal frequency was 2000 Hz and two noise levels were used: 20 and 50 dB N0. The relations proposed by Bilger among critical-bandwidth estimates from band-narrowing experiments, critical-ratio estimates from pure-tone detection in wideband noise, and intensity discrimination for a critical-band-wide noise in wideband noise are not supported by the results of individual listeners, or results averaged across listeners.