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N I Durlach

Publications and source records attributed to N I Durlach.

At least 55 records · Page 3Linked to original sources
PubMed1986

Towards a model for discrimination of broadband signals.

The conventional model for broadband discrimination assumes that resolution is limited by peripheral internal noise that is statistically independent across channels. In this paper, we extend this model in a number of directions. In particular, we compute, compare, and discuss the effects of interchannel correlation and central noise on the sensitivity index d', for discrimination of overall level and discrimination of spectral shape.

Auditory Perception↗
PubMed1986

Interaural magnification.

In principle, magnification of interaural differences, as could be achieved by the use of an enlarged head, will improve auditory spatial perception. This note presents some preliminary thoughts and observations on a signal-processing scheme for interaural magnification.

Auditory Perception↗
PubMed1986

Multichannel syllabic compression for severely impaired listeners.

Two listeners with congenital hearing losses characterized by flat audiograms and dynamic ranges of 18-33 dB were tested with three compression systems and one (reference) linear amplification system. The compression systems placed progressively larger amounts of speech energy within the listener's residual dynamic range, by raising to audibility and compressing 25, 50, and 90 percent of the short-term input amplitude distribution in each of 16 frequency bands. The comparison linear system was defined by adjusting six octave-wide bands of speech to comfortable levels. System performance was evaluated with nonsence CVC syllables presented at a constant input level and spoken by two talkers. Extensive training was provided to ensure stable performance. The results were notably speaker-dependent, with compression consistently providing better performance for one speaker, linear amplification for the other. Averaged over speakers, however, there was no net advantage for any of the compression systems for any listener. The use of high compression ratios and large input ranges tended to degrade perception of initial consonants and vowels. Under some conditions, however, final consonant scores were higher with compression than with linear amplification. Compression generally enhanced the distinction between stops and fricatives, but degraded spectral-concentration and relative-intensity cues required to identify place of articulation.

Adult↗
PubMed1985

Speaking clearly for the hard of hearing I: Intelligibility differences between clear and conversational speech.

This paper is concerned with variations in the intelligibility of speech produced for hearing-impaired listeners under two conditions. Estimates were made of the magnitude of the intelligibility differences between attempts to speak clearly and attempts to speak conversationally. Five listeners with sensorineural hearing losses were tested on groups of nonsense sentences spoken clearly and conversationally by three male talkers as a function of level and frequency-gain characteristic. The average intelligibility difference between clear and conversational speech averaged across talker was found to be 17 percentage points. To a first approximation, this difference was independent of the listener, level, and frequency-gain characteristic. Analysis of segmental-level errors was only possible for two listeners and indicated that improvements in intelligibility occurred across all phoneme classes.

Adult↗
PubMed1985

Research on the Tadoma method of speech communication.

In Tadoma, speech is received by placing a hand on the talker's face and monitoring actions associated with speech production. Our initial research has documented the speech perception, speech production, and linguistic abilities of deaf-blind individuals highly trained in Tadoma. This research has demonstrated that good speech reception can be achieved through the tactile sense: Performance is roughly equivalent to that of normals listening in noise or babble with a signal-to-noise ratio in the range 0-6 dB. It appears that the principal cues employed are lip movement, jaw movement, oral airflow, and laryngeal vibration, and that the errors which occur are caused primarily by inadequate information on tongue position. Our current research includes (1) learning of Tadoma by normal subjects with simulated deafness and blindness, (2) augmenting Tadoma with a supplemental tactile display of tongue position, and (3) developing a synthetic Tadoma system in which signals recorded from a talker's face are used to drive an artificial face. This research is expected to increase our understanding of Tadoma and its relation to other tactile communication methods, show that performance obtained through Tadoma does not represent the ultimate limits of the tactile sense, and provide a research tool for studying transformations of Tadoma.

Adult↗
PubMed1985

Discrimination and identification of frequency-lowered speech in listeners with high-frequency hearing impairment.

The effects of frequency lowering on consonant perception were studied in four listeners with high-frequency sensorineural loss. Frequency lowering, accomplished by pitch-invariant nonuniform compression of the short-term spectral envelope, included lowering to bandwidths of 2500 and 1250 Hz. Performance on frequency lowering was compared to that obtained with linear amplification using uniform or high-frequency emphasis. Results of pairwise discrimination tests indicated that performance on lowering to 1250 Hz was inferior to that obtained with linear amplification. After training, performance on consonant identification with lowering to bandwidths of 2500 or 1250 Hz was equivalent or inferior to that obtained with linear amplification, depending on the subject. In most cases, the performance of the impaired subjects on a given lowering condition was inferior to that obtained by normal subjects, except for one impaired subject whose performance on two lowering conditions was similar to normal.

Hearing Loss, Sensorineural↗
PubMed1984

Intensity perception. XIII. Perceptual anchor model of context-coding.

In our preliminary theory of intensity resolution [e.g., see N. I. Durlach and L. D. Braida, J. Acoust. Soc. Am. 46, 372-383 (1969)], two modes of memory operation are postulated: the trace mode and the context-coding mode. In this paper, we present a revised model of the context-coding mode which describes explicitly a process by which sensations are coded relative to the context and which predicts a resolution edge effect [L. D. Braida and N. I. Durlach, J. Acoust. Soc. Am. 51, 483-502 (1972); J. E. Berliner, L. D. Braida, and N. I. Durlach, J. Acoust. Soc. Am. 61, 1256-1267 (1977)]. The sensation arising from a given stimulus presentation is coded by determining its distance from internal references or perceptual anchors. The noise in this process, combined with the sensation noise, constitutes the limitation on resolution in the model. In the revised model the probability density functions of the decision variable are not precisely Gaussian (and cannot be expressed analytically in closed form). This paper outlines the predictions of the model for one-interval paradigms and for fixed-level two-interval paradigms and derives estimates of the values of model parameters.

Discrimination Learning↗
PubMed1983

Intensity perception. XII. Effect of presentation probability on absolute identification.

Identification experiments using 13 tone-pulse stimuli (1000 Hz, 500 ms) spaced by equal decibel increments from 42 to 90 dB SPL were conducted under three conditions: all intensities equally likely (denoted Q), the middle intensity presented on roughly 1/3 of the trials (M), and each of the extreme intensities presented on roughly 1/5 of the trials (E). Experiments were performed both with and without feedback, and results were analyzed in terms of sensitivity and bias. Similar results were obtained with and without feedback: listeners generally shifted biases in the M and E conditions relative to the Q condition to increase percent-correct scores, but there were only minor changes in sensitivity from condition to condition. However, sensitivities were generally higher and biases more optimal when feedback was available. The results on sensitivity are consistent with those associated with payoff variation [Lippmann et al., J. Acoust. Soc. Am. 59, 129-134 (1976)], but are inconsistent with those reported for presentation probability variation in tone frequency identification [Cuddy et al., J. Exp. Psychol. 100, 218-220 (1973)]. In an auxilliary experiment concerned with tone frequency identification, results consistent with those obtained for intensity, but inconsistent with those reported by Cuddy et al., were obtained.

Feedback↗
PubMed1983

Discrimination of speech processed by low-pass filtering and pitch-invariant frequency lowering.

Consonant discriminability by normal-hearing listeners was studied for monosyllables processed using frequency lowering with either uniform (linear) or nonuniform (warped) compression of the frequency axis. The bandwidth of the compressed signal was either 2500 or 1250 Hz and five compression characteristics were studied, in addition to low-pass filtering, for each of the two bandwidths. Stimuli were 24 consonant-vowel syllables made up of 24 consonants and three vowels, recorded three times by each of two male and female speakers. A "roving-speaker, roving-vowel, roving-utterance," two-interval, forced-choiced procedure with feedback was employed. As expected, performance for the 2500-Hz bandwidth was superior to that for the 1250-Hz bandwidth. For each bandwidth, compression schemes which accomplished greater lowering of the high frequencies relative to the low frequencies resulted in the highest performance. Overall performance for the best frequency-lowering system studied, however, was roughly comparable to that obtained for low-pass filtering. Patterns of performance over articulatory features were different for frequency lowering and filtering. In general, lowering was superior to filtering for contrasts of fricative sounds but inferior for contrasts of nasals and semivowels.

Female↗
PubMed1982

Analytic study of the Tadoma method: identification of consonants and vowels by an experienced Tadoma user.

Performance on identifying consonant and vowel stimuli through the Tadoma methods of speechreading was studied for a deaf-blind, experienced user of Tadoma. For a set of 24 consonants in CV syllables, performance averaged 55%. For a set of 15 vowels and diphthongs in CVC syllables, performance averaged 56%. Confusion matrices derived from the identification tests were analyzed for performance on a set of articulatory/phonological features, the results of the feature analysis for consonants indicated that the features voicing, lip rounding frication, and place were well-perceived; for vowels, and features lip rounding, tenseness, and vertical lip separation were well-perceived.

Adult↗
PubMed1982

Analytic study of the Tadoma method: further experiments with inexperienced observers.

Results are presented for two studies of speechreading through the Tadoma method using normal subjects with simulated deafness and blindness. In the first study, subjects received training on the identification of consonant and vowel stimuli through Tadoma. In posttraining tests, an average score of 73% was obtained on a set of 24 consonants presented in CV syllables, and an average score of 82% was obtained on a set of 15 vowels and diphthongs presented in /g/-V-/d/ syllables. An analysis of the confusion matrices derived from the identification tests in terms of of various articulatory/phonological features indicated that the features place, voicing, frication, and round were well-perceived for consonants and round, tense, vertical lip separation, and low, for vowels. In the second study, subjects received training through Tadoma on comprehension of sentences composed of words from a 43-item vocabulary. In tests for which sentence stimuli were repeated until a correct response was obtained, the subjects identified an average of 30% of the words correctly on the first presentation and required an average of roughly four presentations for complete identification of the stimulus.

Humans↗
PubMed1982

Tactile communication of speech: II. Comparison of two spectral displays in a vowel discrimination task.

Vowel discrimination experiments were performed comparing two tactile, Optacon-based, spectral displays: a frequency-amplitude (FA) display and a time-swept (TS) display. The set of vowel pairs tested consisted of all pairs from the set of ten American nondipthongized vowels. One set of materials consisted of natural /b/-V-/t/'s (with each vowel represented by 12 utterances generated by four speakers producing each vowel three times). A second set consisted of synthetic vowels (with each vowel represented by a single waveform). On the average, th score obtained with the second set of materials was substantially better than with the first (92% vs 79%); the score obtained with the TS display was slightly better than with the FA display (87% vs 83%); the feature best differentiated was tenseness, followed by the features high and low, then by round and back, and finally by retroflexion; and the correlation between discrimination performance and the physical parameters duration, amplitude, F1, and F2/F1 (taken singly) was relatively weak. In general, the results of this study, together with those of other studies previously reported, suggest that the two displays studied are far from optimum.

Data Display↗
PubMed1981

Study of multichannel amplitude compression and linear amplification for persons with sensorineural hearing loss.

Experiments were conducted on five listeners with sensorineural hearing impairments using two 16-channel, computer-controlled, amplitude compression systems, and four linear systems. One of the compression systems was designed to restore normal equal loudness contours, the other employed reduced high-frequency emphasis and reduced compression ratios. The linear systems differed only in their frequency-gain characteristics (orthotelephonic plus three characteristics with high-frequency emphasis that were expected to produce better results than orthotelephonic). In the main experiment, all systems were compared for each listener using nonsense CVC monosyllables and sentence materials spoken by male and female talkers and presented in quiet/anechoic and noisy/reverberant environments at the most comfortable level for each listener. The linear systems with high-frequency emphasis performed substantially better than the orthotelephonic system. Performance with compression was generally slightly worse than with linear amplification. Compression was superior to linear amplification only when speech materials with significant item-to-item level variation were used in quiet with subjects with more severe losses and when reduced input speech levels were used. To the extent that these two conditions represent real-life communication conditions, these results suggest that compression is preferable to linear amplification in a wearable hearing aid.

Adult↗
PubMed1981

Binaural interaction of impaired listeners. A review of past research.

This paper reviews past studies of binaural interaction in impaired listeners. The topics covered include localization and lateralization; equal loudness, centering and lateralization adaptation; detection of signals in noise; and discrimination of interaural time delay and interaural amplitude ratio. Comments concerning experimental design and procedures, as well as interpretation of results, are often included with descriptions of the studies.

Auditory Perception↗
PubMed1980

Intensity perception. X. Effect of preceding stimulus on identification performance.

This article describes some results on the effect of the preceding stimulus on performance in an intensity-identification experiment with feedback. Based on previous research and our own subjective experiences as listeners, we had expected that sensitivity would increase when the intensities of the preceding and current stimuli were close together. The results of our experiments show, however, that this is not the case: sensitivity is indepenent of the preceding stimulus. The fact that the response variance tends to decrease when the intensities of the preceding and current stimuli are close together is found to be caused solely by sequential effects in response bias. These findings create an interesting puzzle concerning the mechanism by which feedback improves sensitivity in identification. Apparently, the most obvious hypothesis--namely, that the feedback enables the previous stimulus to be used as a standard for judging the current stimulus--is false.

Acoustic Stimulation↗
PubMed1980

Intensity perception XI. Experimental results on the relation of intensity resolution to loudness matching.

According to a recent extension of our theory of intensity perception [Lim et al., J. Acoust. Soc. Am 62, 1256-1267 (1977)], two stimuli are matched in loudness if and only if their intensities divide the respective dynamic ranges proportionally in terms of just noticeable differences. This study reports results of intensity discrimination and loudness matching experiments designed to test this prediction. Data were obtained over most of the dynamic range for three different types of sounds: a 1000-Hz tone in quiet, a 1000-Hz tone partially masked by a 2-octave band of noise, and spectrally flat wide-band noise. Of the five subjects tested, three produced results that had sufficient internal consistency to be useful for testing the predictions. For these subjects, the data and the theory were found to be reasonably consistent. Comparison with other studies, however, reveals that loudness matching results vary with matching paradigm by an amount that is significant with respect to the task of evaluating the theory. Hence, a rigorous test of the theory requires an improved understanding of the effects of matching paradigm.

Humans↗