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L D Braida

Publications and source records attributed to L D Braida.

53 records · Page 3Linked to original sources
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↗
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↗
PubMed1978

Analytic study of the Tadoma method: discrimination ability of untrained observers.

This study reports the ability of two observers with normal-hearing and sight to discriminate pairs of speech elements through the Tadoma method of speechreading. The observers were blindfolded and exposed to masking noise to eliminate visual and auditory cues. They placed their right hand over the speaker's face and neck so that the thumb rested lightly on the lips and the fingers fanned out over the cheek and neck. The discrimination tests were conducted using an ABX procedure. Average discrimination scores for the five types of test materials used in the ABX tests were 87% on W-22 words, 83% on Modified Rhyme Test words, 70% on vowels, 77% on CV and VC nonsense syllables, and 71% on consonant clusters. In all of the ABX tests, the inexperienced observers performed at least as well as the experienced Tadoma user studied by Norton, et al (1977). This finding indicates that the basic tactile sensitivity of inexperienced observers is comparable to that of an experienced deaf-blind Tadoma user.

Cues↗
PubMed1978

Intensity perception. IX. Effect of a fixed standard on resolution in identification.

This note reports some measurements of the changes in identification performance that result form presenting a fixed standard before each trial. These measurements indicate that the presence of the standard improves performance for test stimuli in the vicinity of the standard, except when the standard is near the extremes of the stimulus range.

Discrimination, Psychological↗
PubMed1977

Analytic study of the Tadoma method: background and preliminary results.

Certain deaf-blind persons have been taught, through the Tadoma method of speechreading, to use vibrotactile cues from the face and neck to understand speech. This paper reports the results of preliminary tests of the speechreading ability of one adult Tadoma user. The tests were of four major types: (1) discrimination of speech stimuli; (2) recognition of words in isolation and in sentences; (3) interpretation of prosodic and syntactic features in sentences; and (4) comprehension of written (Braille) and oral speech. Words in highly contextual environments were much better perceived than were words in low-context environments. Many of the word errors involved phonemic substitutions which shared articulatory features with the target phonemes, with a higher error rate for vowels than consonants. Relative to performance on word-recognition tests, performance on some of the discrimination tests was worse than expected. Perception of sentences appeared to be mildly sensitive to rate of talking and to speaker differences. Results of the tests on perception of prosodic and syntactic features, while inconclusive, indicate that many of the features tested were not used in interpreting sentences. On an English comprehension test, a higher score was obtained for items administered in Braille than through oral presentation.

Adult↗
PubMed1977

Intensity perception. VIII. Loudness comparisons between different types of stimuli.

In this paper, we describe an extension of our preliminary theory of intensity resolution [Durlach and Braida, J. Acoust. Soc. Am. 46, 372-383 (1969)] to include loudness comparisons among different types of stimuli. The extended theory relates mean loudness matches to discrimination and provides a framework for the interpretation of results on the intrasubject variability of loudness comparisons. The predicted relation between mean loudness matches and discrimination is essentially the same as that proposed by Riesz [J. Acoust. Soc. Am. 5, 211-216 (1933)]. With regard to the variability of loudness comparisons, the extended model is essentially the same as the preliminary model except that a new term is included in the trace-mode memory variance to account for the dissimilarity of the stimuli being compared. The model is compared to some published data on loudness matching and discrimination and to some new data of our own on the variability of loudness comparisons obtained in a two-interval, roving-level, loudness-discrimination experiment.

Acoustic Stimulation↗