Psychoacoustic Tasks Research Articles

Psychoacoustic Performance in Children Completing Fast ForWord Training

It has been hypothesized that one cause of children's language disorders is poor temporal processing. When children are not able to follow the rapid modulations in the speech signal that cue phonemic information, development of critical language concepts might be missed. It has also been suggested that intensive auditory training on a hierarchy of temporal tasks may significantly improve language processing. Temporal processing was evaluated in children with normal language and those with language impairment who were enrolled in an intensive computerized auditory training program. The psychoacoustic tasks were aimed at evaluating the ability to (1) process signals arriving in very close succession, and (2) discriminate signals changing rapidly in frequency. Three dependent variables included thresholds for brief tones presented in three conditions: quiet, just before a masker, and simultaneously with a masker. A fourth dependent variable was the minimum detectable change in a tone sweeping up in frequency. Despite minimal changes in performance over the five-week period, there were overlaps in performance on all tasks between the groups suggesting a complex relationship between temporal processing and language development. Children with language impairment who had better performance on the masking and frequency discrimination tasks showed greater success on the auditory training program.

Language-specific knowledge and the perception of tonal contrasts in Italian and English

Intonation, including details of tonal alignment [i.e., the synchronization of tones and segments (D’Imperio, 2000)], has been claimed to be part of the phonological knowledge of native speakers. This linguistic knowledge can be assumed to influence the perception of tonal contrasts. Both American English and Neapolitan Italian have two rising pitch accents (L+H* and L*+H) whose alignment is contrastive, although details of their implementation differ. The accents also cue different pragmatic functions (e.g., cuing the question/statement contrast only in Neapolitan) and are subject to different syntagmatic constraints in the two languages. This study tested the hypotheses that the American listeners would be able to perceive the contrast between the two Neapolitan accents, despite the aforementioned differences, and that they would respond similarly to a linguistic (question/statement) and a psychoacoustic (early/late peak) identification task. The stimuli were constructed by manipulating the alignment of a Neapolitan utterance through PSOLA. These stimuli were employed in a linguistic task for both language groups and a psychoacoustic task for the Americans only. Although the Americans could perform the linguistic task, scoring similarly to the Neapolitans, they could not perform the categorization in the psychoacoustic task. The results bear upon the ‘‘universality’’ of tonal perception.

Onset overmasking of a brief amplitude increment in a pure tone and sensorineural hearing impairment.

The goal of this investigation was to determine, in patients with sensorineural hearing loss who may show an audiologic alteration in onset overmasking, whether different pathologic conditions differ in this respect, and whether patients with a vestibular neurotomy damaging the cochlear efferents will be affected. Auditory detection of brief signals, when presented at the beginning of a simultaneous long masking sound, may require a higher acoustic level than when presented after several hundred milliseconds. The proposed explanation, in terms of auditory nerve fibers adaptation has been based on the observation of a proportionally smaller increase of firing in response to an amplitude increment at the onset of a stimulus. However, this may not explain all the data, and other underlying processes are certainly involved. The degree or type of sensorineural pathologic condition may be a contributing factor. In addition, the cochlear efferent system, which exhibits a time course and a high-frequency predominance compatible with that of onset overmasking, could be involved. Onset overmasking of a brief amplitude increment in one pure tone was examined in 6 normal subjects, 12 patients who had undergone vestibular neurotomy, 8 subjects with Meniere's-like symptoms, 5 subjects with presbyacusis, and 3 patients with a small neuroma. Both ears of all subjects were tested. Detection thresholds, amount of onset overmasking, and differences between the two ears were examined. All results from subjects with presbyacusis and neuroma were within the range observed in the group of normal subjects. In the group of eight Ménière's syndrome patients, four had results outside the normal range, three had deteriorated detection, and one had better detection. Among the 12 subjects who had undergone neurotomy, 2 had better detection in the unoperated ear. The results from Ménière's patients indicate that, in addition to the previously reported improved detection threshold for short onset delay, a deterioration of detection thresholds may occur in some subjects. Overall, the results from neurotomized ears do not provide evidence for an involvement of cochlear efferents in this tested psychoacoustic task.

The effect of age on temporal integration

The present study was designed to assess the effects of age, independent of hearing loss, on temporal integration of sinusoidal signals. Thresholds for detecting a 1000-Hz sinusoid as a function of signal duration were measured for signal durations ranging from 20–500 ms. The signal had a rise/fall time of 10 ms. Subjects were younger (18–22) and older (over age 65) adults with normal hearing (thresholds less than 20 dB HL) for frequencies of 4 kHz and below. At the shortest signal duration (20 ms), thresholds for both groups were elevated approximately 16 dB relative to their thresholds for the 500-ms signal. Both older and younger adults also exhibited similar decreases in threshold as a function of signal duration. Overall, the findings suggest that unlike most temporally based psychoacoustic tasks, temporal integration of sinusoids remains relatively unchanged as a function of age.

Classification of the acoustic environments using a psychoacoustic model

Complex digital hearing aid algorithms employ different signal processing stages, e.g., noise reduction and loudness control. Most of these stages are suitable only for special acoustic environments or need different parameter sets for different environments to assure optimum rehabilitation success. Future ‘‘intelligent’’ digital hearing aids should therefore incorporate a model of the acoustic environment to adapt the signal processing to the acoustic environment. In particular, the presence of a speech signal and of different types of ambient noise should be detectable. In this study, the perception model introduced by Dau et al. [J. Acoust. Soc. Am. 102, 2829–2919 (1996)], which was originally developed to model different psychoacoustical tasks, e.g., forward masking and modulation detection is used as a preprocessor for this type of classification algorithms. This approach seems promising, as the model includes a modulation frequency analysis which was shown to be a good estimator of speech activity [Ostendorf, Fortschritte der Akustik DAGA 98, Zürich]. First results on the classification accuracy using this model are presented.

Individual noise sensitivity and performance on psychoacoustic tasks

In environmental noise surveys, self-reported noise sensitivity turned out to be a major predictor of noise-annoyance reactions. Its relationship to basic measures of auditory functioning, however, has not been systematically explored yet. Therefore, in the present investigation, a sample of 61 unselected listeners was subjected to a battery of psychoacoustic laboratory 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’’ versus ‘‘high’’ noise sensitivity on the basis of scores obtained from a psychometrically evaluated questionnaire [K. Zimmer and W. 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.

Speech perception in children with specific reading difficulties (dyslexia).

Many experimental studies over the last two decades have suggested that groups of children who suffer significant delay in reading also show a weakness in phoneme discrimination and identification. In order to look further at the relation between type of reading deficit, auditory acuity, and speech discrimination, a group of 13 children with specific reading difficulty (SRD), 12 chronological-age controls, and 12 reading-age controls were tested on a battery of speech-perceptual, psychoacoustic, and reading tests. A sub-group of children with Specific Reading Difficulty (SRD) were poor at speech discrimination tests, whereas the rest of the SRD group performed within norms. For this sub-group, discrimination performance was particularly poor for consonant contrasts differing in a single feature that was not acoustically salient, and problems were encountered with nasal and fricative contrasts as wells with stop contrasts. These children did not differ from controls in their performance on non-speech psychoacoustic tasks. An evaluation is made of the reported phonemic awareness skills of beginning readers with regard to speech-processing issues which may help in understanding what factors are important in reading development.

Effect of otoacoustic emissions on just-noticeable differences for intensity in normally hearing subjects

Measurements of spontaneous and click-evoked otoacoustic emissions (OAEs) were used to classify listeners with normal hearing into one of two categories--those with spontaneous emissions (SOAEs) and high-level transiently evoked emissions (TEOAEs) in both ears (strong emissions) and those with no SOAEs and low-level TEOAEs in either ear (weak emissions). Just-noticeable differences (jnd's) in intensity for 1-kHz pure tones presented at either 60, 40, or 20 dB SL were determined for these two groups using a continuous pedestal technique. Mean jnd's for intensity for the two groups did not differ significantly. Intratest variability was compared and the group with strong emissions had significantly higher variability for presentation levels of 20 dB SL and lower variability at 60 dB SL. Additional testing of intensity jnd's was performed in individuals with strong emissions using pure tones 30 Hz lower than a targeted SOAE frequency. Large interindividual differences were present without a specific pattern. It is concluded that OAE activity level does not affect the mean jnd for intensity discrimination. Individuals with strong emissions have less variance when performing the test at higher levels and more variance for lower level stimuli than do individuals with weak emission characteristics. Because an ear's OAE characteristics can alter performance on psychoacoustic tasks, knowledge of such characteristics is desirable when psychoacoustic results are acquired and reported.

Short‐term temporal integration at high‐frequencies: Evidence for the influence of peripheral nonlinearity?

Temporal integration in the auditory system can be modeled by a compressive nonlinearity followed by a temporal integrator. For a fixed integrator, the more compressive the nonlinearity, the greater the effective integration. Compressive nonlinearity on the basilar membrane is marked at medium levels, but is reduced at low and high levels. To assess whether this influences temporal integration, thresholds of a 6.5‐kHz sinusoid were measured in the presence of a long‐duration broadband‐noise masker as function of signal duration, using three different noise spectrum levels, −10, 20, and 50 dB (re: 20 μPa). Signal level dB was plotted against log(time) for each level. For signal durations between 20 and 200 ms, there was no significant difference in the slopes of the three functions. However, between 1 and 10 ms the slope of the function for the mid‐level masker was steeper by a factor of between 1.5 and 2. This is consistent with the greater mid‐level compression on the basilar membrane, if one assumes a fixed short‐term temporal integrator. Performance in other psychoacoustic tasks, including differences between normal‐hearing and hearing‐impaired listeners, is also discussed in terms of peripheral processing. [Work supported by the MRC, EPSRC, and Meridian Audio (UK).]

Training transfer in simple psychoacoustic tasks

This paper reports preliminary results about the extent to which the learning curve in one psychoacoustic task is altered by practice in another psychoacoustic task. The primary interest in training transfer is motivated by the idea that variations in training transfer across tasks is closely related to structural properties of the perceptual system under consideration and, therefore, that results on training transfer should be useful in forming hypotheses about these properties. The tasks considered in this studies are frequency and intensity discrimination and the variables across which training transfer is being measured include, in addition to frequency versus intensity and left ear versus right ear, reference frequency, reference intensity, and increment size. [The authors are indebted to Lucia Vaina of Boston University for inspiring this research by informing them of equivalent work currently being conducted in the area of visual psychophysics.]

A model of the effective auditory signal processing. I: Masking experiments

A model is described that simulates the detection characteristics of the human auditory system for different psychoacoustical tasks. An optimal detection process is attached to the model after the preprocessing stages. The statistical basis was provided by the assumption of an internal Gaussian noise following nonlinear processing in the peripheral auditory system. The nonlinear processing describes essential features of human temporal processing, such as forward masking, temporal integration, and dynamic range compression. Simulations and measurements of backward, simultaneous, and forward masking are presented employing deterministic (frozen) and stochastic (running) broadband noise maskers. The stimuli were presented to the model in an paradigm (adaptive forced-choice procedure) identical to the one used with human subjects. In most cases, a very good agreement between simulated and measured thresholds is achieved.

Psychoacoustical contribution of each lateral lemniscus

Although each lateral lemniscus is required for sound localization in its contralateral hemifield, no auditory function is yet known for the neural activity evoked in the lemniscus ipsilateral to a sound source. In an attempt to assess the role played by the ipsilateral lemniscus, monaural cats were tested on an array of psychoacoustical tasks before and after surgical section of one or the other lateral lemniscus. The results show that the lemniscus contralateral to the remaining intact ear is either necessary or sufficient for 24 of the 26 tests administered. However, the lemniscus ipsilateral to the intact ear is both necessary and sufficient (or alternatively, the contralateral lemniscus makes no obvious contribution) to normal thresholds in two of the tasks: detection of low-frequency tones (< 4 kHz) and detection of low-frequency AM modulation. Because of their projections to the ipsilateral inferior colliculus via the ipsilateral lateral lemniscus, the anatomical substrate of these two unusual tasks is probably the fibers from the MSO and possibly, the LSO, ipsilateral to the intact ear.

Sources of auditory masking in infants: Distraction effects

Previous work has demonstrated that infants' thresholds for a pure tone are elevated by a masker more than would be predicted from their critical bandwidths. The present studies explored the nature of this additional masking. In Experiment 1, detection thresholds of 6-month-old infants and of adults for a 1-kHz tone were estimated under three conditions: in quiet, in the presence of a 4- to 10-kHz bandpass noise at 40 dB SPL, and in the presence of the same noise at 50 dB SPL. The noise was gated on at the beginning of each trial. Adult thresholds were the same in all three conditions, indicating that little or no sensory masking took place in the presence of the noise. Infant thresholds were about 10 dB higher in the presence of the noise. We term this effect distraction masking. In Experiment 2, the effect of gating the noise on at trial onset was examined. Thresholds for the same tone were estimated in quiet and in the presence of the band-pass noise at 40 dB SPL, but the noise was presented continuously during the session. Under these conditions, distraction masking was still observed for infants. These findings suggest that a masker can have nonsensory effects on infants' performance in a psychoacoustic task.

Discrimination of syllable duration in English and French short sentences

Two experiments were conducted in order to study the perceptual discrimination of syllable duration within sentences. Two natural French sentences and one English sentence, each consisting of eight syllables were resynthesized with 15% increases and decreases in syllable duration up to ± 60%. The modified, then randomized, stimuli were presented once to 20 subjects whose task was to judge how natural they sounded (experiment I). The same stimuli were then used to determine whether the modifications in duration were perceptible (experiment II). The results provide evidence of the fact that judgment of the rhythmic quality of sentences (a psycholinguistic task) and temporal discrimination (a psychoacoustic task) both have the same functional basis. The differential limen found in two experiments for both languages is remarkably similar and its estimated value is approximately 25% for an average syllable duration.

Individual differences in auditory capabilities. I.

Twenty-eight audiometrically normal adult listeners were given a variety of auditory tests, ranging from quiet and masked thresholds through the discrimination of simple and moderately complex temporal patterns. Test-retest reliability was good. Individual differences persisted on a variety of psychoacoustic tasks following a period of training using adaptive threshold-tracking methods, and with trial-by-trial feedback. Large individual differences in performance on temporal-sequence-discrimination tasks suggest that this form of temporal processing may be of clinical significance. In addition, high correlations were obtained within given classes of tests (as, between all tests of frequency discrimination) and between certain classes of tests (as, between tests of frequency discrimination and those of sequence discrimination). Patterns of individual differences were found which support the conclusion that individual differences in auditory performance are, in part, a function of patterns of independent abilities.

Midfrequency dysfunction in listeners having high-frequency sensorineural hearing loss.

Two-tone unmasking, psychophysical tuning curves and pure-tone masking patterns were measured at 500 and 1000 Hz in 17 listeners having high-frequency sensorineural hearing loss due to noise exposure. Results were compared to similar data obtained from 20 normal-hearing young adults. In addition, measures of word-recognition ability were obtained in quiet and in noise for both groups. The primary findings were as follows: (a) 29% (n = 5) of the hearing-impaired subjects exhibited abnormal results on at least one of the psychoacoustic tasks investigated; (b) the observed abnormalities were reliable; and (c) there appeared to be a relation between the presence of midfrequency dysfunction and degree of difficulty on word-recognition tasks. These results and their implications are discussed.

Pure tone pitch perception and low-frequency hearing loss.

Pitch perception for pure tones was investigated in a group of listeners with low-frequency sensorineural hearing loss. Pitch judgments from each listener were compared with results from psycho-acoustic tasks which provide information on the "place" of cochlear response. The pitch measures employed were: (1) binaural pure-tone pitch matching in a listener with unilateral hearing loss, (2) octave judgments in listeners with musical ability, and (3) pitch-intensity functions in other listeners. Cochlear place of response was inferred from psychophysical tuning curves (PTC's). Two distinct types of PTC's for low-frequency probe tones were observed. Three listeners demonstrated "abnormally tuned" PTC's. For these listeners the frequencies that were most effective at masking the probe were considerably higher than the probe frequency. The three remaining listeners demonstrated "normally tuned" PTC's. Listeners with abnormally tuned PTC's were suspected of having an extremely abnormal place of response for low-frequency tones; this response pattern being located more toward the base of the cochlea than in the listeners with normally tuned PTC's. Sensitivity thresholds measured in the presence of high-pass masking noise supported this hypothesis. Small pitch-frequency irregularities were observed in many listeners, although they were not consistently related to the inferred place of response for that frequency. The individual listeners' pitch judgments failed to distinguish between two types of PTC's. In particular, listeners who demonstrated abnormally tuned PTC's did not exhibit correspondingly large pitch irregularities. These results are difficult to explain on the basis of a classical "place" theory of pitch perception.

Psychoacoustic and phonetic temporal processing in normal and hearing-impaired listeners

Four measures of auditory temporal processing were obtained from 16 normals and 16 individuals with a hearing loss of heterogeneous origin. These measures were: (1) temporal integration—the difference in detection thresholds between signals of 10- and 1000-ms duration (which was determined to provide an estimate of the ability to integrate energy over time), (2) gap detection—the shortest duration of silence between two noise bursts that can be discriminated from an uninterrupted noise, (3) temporal difference limen—the increment in duration necessary to detect a difference in the duration of a noise burst, (4) gap difference limen—the increment in duration necessary to detect a difference in the duration of a silent interval between two noise bursts. Each measure was obtained for stimuli centered both at 500 and at 4000 Hz using a three-alternative forced-choice procedure. In addition, measures of identification and discrimination were obtained for two sets of synthetic speech syllables varying chiefly in a temporal parameter, voice-onset-time, from /ba/ to /pa/ and from /bi/ to /pi/. Finally, speech identification in noise was measured with the FAAF test. Most of the hearing-impaired listeners displayed poorer temporal analysis than the normals on all of the psychoacoustical tasks, regardless of whether the two groups were compared at similar sound pressure levels or at similar sensation levels. Although the hearing-impaired listeners displayed a reduction in the ability to discriminate subphonemic cues for the voiced–voiceless distinction, their identification of that distinction in stop consonants appeared to be normal. The hearing-impaired group made about twice as many errors as did the normals on each of the consonant features of place, manner, and voicing when identifying speech in noise. Increased temporal difference limen and longer gap-detection thresholds were found to correlate significantly with reduced speech intelligibility in noise, even when the effects of the pure-tone threshold loss were partialed out.

Midfrequency dysfunction in noise‐exposed persons

Several recent reports have observed that persons having high‐frequency sensorineural hearing loss attributed to noise exposure exhibit abnormal performance on various suprathreshold psychoacoustic tasks for stimuli confined to the midfrequency region where hearing thresholds are normal. It has also been suggested that this apparent midfrequency dysfunction may be partially responsible for the extreme difficulties in understanding speech experienced by some of these individuals. To explore this issue further, the present study measured psychophysical tuning curves, masking patterns and unmasking at 500 and 1000 Hz in 15 listeners having high‐frequency noise‐induced hearing loss. In addition, measures of speech understanding were obtained in quiet and in noise. Results are compared to similar data obtained from normal hearers. [Research supported by grant 1‐R01‐OH00972 from the National Institute of Occupational Safety and Health.]

A model of peripheral auditory processing

A critical‐band based hybrid computer model of cochlear hearing processes has been developed at the Environmental Acoustics Laboratory. The model incorporates elements representative of the mechanical response of the cochlear partition, integration patterns in the organ of corti, inhibitory mechanisms at the cochlea, and some primitive decision processes representative of brain stem Operations. The model has been developed for the Pennsylvania State University's hybrid computer which is a PDP 10 digital computer interfaced with an EAI 680 analog computer. The model's ability to discriminate certain acoustic stimuli has been assessed and its performance is compared to the performance of normal‐hearing listeners on similar psychoacoustic tasks. Implications of the results for hearing theory and for the understanding of mechanisms of cochlear hearing impairment are discussed.