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Biomedical subjects

M F Dorman

Publications and source records attributed to M F Dorman.

At least 55 records · Page 3Linked to original sources
PubMed1987

Vowel intelligibility in the absence of the acoustic reflex: performance-intensity characteristics.

Performance-intensity functions were defined for ten synthetic vowels whose durations (50 ms) were shorter than the time necessary for the acoustic reflex to alter the transmission characteristics of the middle ear. Recognition accuracy for ten listeners with normal auditory function was asymptotic from 72 to 90 dB and then fell linearly to 108 dB. Thus, at SPLs greater than approximately 90 dB, the auditory encoding of vowels is altered by the absence of the acoustic reflex.

Adult↗
PubMed1987

Effects of spectral flattening on vowel identification.

The identification of front vowels was studied in normal-hearing listeners using stimuli whose spectra had been altered to approximate the spectrum of vowels processed by auditory filters similar to those that might accompany sensorineural hearing loss. In the first experiment, front vowels were identified with greater than 95% accuracy when the first formant was specified in a normal manner and the higher frequency formants were represented by a broad, flat spectral plateau ranging from approximately 1600 to 3500 Hz. In the second experiment, the bandwidth of the first formant was systematically widened for stimuli with already flattened higher frequency formants. Normal vowel identification was preserved until the first formant was widened to six times its normal bandwidth. These results may account for the coexistence of abnormal vowel masking patterns (indicating flattened auditory spectra) and normal vowel recognition.

Auditory Perception↗
PubMed1985

Influence of the first formant on the recognition of voiced stop consonants by hearing-impaired listeners.

In order to examine first formant masking effects in hearing-impaired listeners, bay, day, and gay were synthesized with and without a first formant. The signals were presented at several levels. Removal of the first formant did not improve intelligibility at levels above, at, or below the point of maximum intelligibility. These results and others converge to suggest that masking spread from the first formant is not a significant factor in the identification of voiced stop consonants by listeners with sloping, mild-to-moderate hearing loss.

Aged↗
PubMed1985

Phonetic identification by elderly normal and hearing-impaired listeners.

Young normal-hearing listeners, elderly normal-hearing listeners, and elderly hearing-impaired listeners were tested on a variety of phonetic identification tasks. Where identity was cued by stimulus duration, the elderly hearing-impaired listeners evidenced normal identification functions. On a task in which there were multiple cues to vowel identity, performance was also normal. On a/b d g/identification task in which the starting frequency of the second formant was varied, performance was abnormal for both the elderly hearing-impaired listeners and the elderly normal-hearing listeners. We conclude that errors in phonetic identification among elderly hearing-impaired listeners with mild to moderate, sloping hearing impairment do not stem from abnormalities in processing stimulus duration. The results with the /b d g/continuum suggest that one factor underlying errors may be an inability to base identification on dynamic spectral information when relatively static information, which is normally characteristic of a phonetic segment, is unavailable.

Adult↗
PubMed1984

Processing of cues for stop consonant voicing by young hearing-impaired listeners.

To assess whether young hearing-impaired listeners are as sensitive as normal-hearing children to the cues for stop consonant voicing, we presented stimuli from along VOT continua to young normal-hearing listeners and to listeners with mild, moderate, severe, and profound hearing impairments. The response measures were the location of the phonetic boundaries, the change in boundaries with changes in place of articulation, and response variability. The listeners with normal hearing sensitivity and those with mild and moderate hearing impairments did not differ in performance on any response measure. The listeners with severe impairments did not show the expected change in VOT boundary with changes in place of articulation. Moreover, stimulus uncertainty (i.e., the number of possible choices in the response set) affected their response variability. One listener with profound impairment was able to process the cues for voicing in a normal fashion under conditions of minimum stimulus uncertainty. We infer from these results that the cochlear damage which underlies mild and moderate hearing impairment does not significantly alter the auditory representation of VOT. However, the cochlear damage underlying severe impairment, possibly interacting with high signal presentation levels, does alter the auditory representation of VOT.

Adolescent↗
PubMed1983

Susceptibility to intraspeech spread of masking in listeners with sensorineural hearing loss.

Previous research with speechlike signals has suggested that upward spread of masking from the first formant (F 1) may interfere with the identification of place of articulation information signaled by changes in the upper formants. This suggestion was tested by presenting two-formant stop consonant--vowel syllables varying along a/ba--/da/--/ga/ continuum to hearing-impaired listeners grouped according to etiological basis of the disorder. The syllables were presented monaurally at 80 dB and 100 dB SPL when formant amplitudes were equal and when F 1 amplitude was reduced by 6, 12, and 18 dB. Noise-on-tone masking patterns were also generated using narrow bands of noise at 80 and 100 dB SPL to assess the extent of upward spread of masking. Upward spread of masking could be demonstrated in both speech and nonspeech tasks, irrespective of the subject's age, audiometric configuration, or etiology of hearing impairment. Attenuation of F 1 had different effects on phonetic identification in different subject groups: While listeners with noise-induced hearing loss showed substantial improvement in identifying place of articulation, upward spread of masking did not consistently account for poor place identification in other types of sensorineural hearing impairment.

Adult↗
PubMed1981

Identification and discrimination of a synthesized voicing contrast by normal and sensorineural hearing-impaired children.

The identification and discrimination of a stop-consonant voicing contrast (/da/--/ta/) was assessed in children and adolescents who had moderate, severe, and profound sensorineural hearing losses. The location of the perceptual boundary between /da/ and /ta/ did not differ between normal listeners and listeners with moderate losses. Of the ten listeners with severe losses, five evidenced normal boundaries, three evidenced longer-than-normal boundaries, and two could not identify the stimuli at all. Of the three listeners with profound hearing losses, one could identify normally, and two could not identify at all. For the most part, discrimination data mirrored identification data. However, in some instances listeners were able to discriminate between stimuli they could not differentially identify. These subjects appeared to have the auditory capacity to resolve differences in voice-onset-time but could not use this capacity to make phonetic identification.

Adolescent↗
PubMed1981

Shifts in phonetic identification with changes in signal presentation level.

Identification functions for stimuli from a two-formant [bdg] continuum were assessed at three levels of signal presentation: 55, 70, and 90 dB SPL. At 90 dB the [b] category was narrowed, the [d] category virtually eliminated, and the [g] category greatly enlarged. Since high SPLs can alter the identification functions for these simplified speech signals, caution should be exercised when using stimuli of this nature to compare the speech perception abilities of normal hearing and hearing impaired listeners. If high SPLs, independent of cochlear damage, can alter identification functions, then perceptual experiments may best be conducted at equal SPLs rather than at equal SLs.

Hearing Loss, Sensorineural↗
PubMed1980

Identification of synthetic /bdg/ by hearing-impaired listeners under monotic and dichotic formant presentation.

Individuals with sensorineural hearing losses of both flat and sloping configuration evidence difficulty in identifying stop consonant place of articulation. To assess whether upward spread of masking is responsible for this difficulty, we presented hearing-impaired listeners with stimuli from a /ba da ga/ continuum in both monotic and dichotic (F1 to one ear; F2/F3 to the other ear) listening conditions. In the monotic conditions, listeners with similar audiograms evidence great variability in identification performance. In the dichotic conditions performance did not generally improve. For a few listeners, however, the improvement was striking. At moderate levels of signal presentation, upward spread of masking does not appear to be responsible for the poor identification of place by the majority of listeners with moderate hearing losses.

Adolescent↗
PubMed1980

Distribution of acoustic cues for stop consonant place of articulation in VCV syllables.

Most theoretical accounts of the identification of stop consonant place of articulation have focused on how bursts and formant transitions conspire to signal place in CV syllables. In the present series of experiments we have examined the identification of place in VCV syllables and have found that not only do the burst and opening transitions affect the judgement of place, but so also do the closing transitions and the duration of the closure interval. This outcome is consistent with the outcomes of many other experiments in showing that there are multiple acoustic events which bear on the identification of a given phone and that those acoustic events are distributed over time. Theoretical accounts of place identification based on data of this kind may prove viable than theories based on data from the identification of place in the absolute, syllable-initial position.

Humans↗
PubMed1979

Some experiments on the sound of silence in phonetic perception.

The results of several experiments demonstrate that silence is an important cue for the perception of stop-consonant and affricate manner. In some circumstances, silence is necessary; in others, it is sufficient. But silence is not the only cue to these manners. There are other cues that are more or less equivalent in their perceptual effects, though they are quite different acoustically. Finally, silence is effective as a cue when it separates utterances produced by male and female speakers. These findings are taken to imply that, in these instances, perception is constrained as if by some abstract conception of what vocal tracts do when they make linguistically significant gestures.

Cues↗
PubMed1976

Hemispheric specialization for speech perception in four-year-old children from low and middle socio-economic classes.

Four-year-old male and female children from low and middle socio-economic class (SEC) were presented a dichotic syllable task. Both low and middle SEC males evidenced significant right-ear advantages. Neither low nor middle SEC females evidenced a significant right-ear advantage. The similar ear advantage in the low and middle SEC populations replicates a previous study with six-year-olds and suggests that the variations in rearing conditions which occur in low and middle SEC classes does not affect hemispheric lateralization for speech perception.

Auditory Perception↗
PubMed1975

Hemispheric lateralization for speech perception in stutterers.

Sixteen adult, right-handed, moderate-to-severe atutterers (12 males, 4 females) and 20 nonstuttering controls (10 males, 10 females) were given a dichotic nonsense-syllable test to determine hemispheric lateralization for speech. Both male and female stutterers evidenced right-ear advantages in syllable identification similar in magnitude to those found for normals. These data confirm other reports of no difference in cerebral speech lateralization for stutterers and nonstutterers and, therefore, lend no support to theories that relate stuttering to abnormalities in cerebral lateralization. Acknowledgments. This study was conducted while the authors were at the University of Connecticut, Storrs. The assistance of Dr. R. L. Webster, the staff of the Institute for Behavioral Research, and the Departments of Psychology and Linguistics at the University of Connecticut is gratefully acknowledged.

Auditory Perception↗
PubMed1975

Vowel and nasal duration as cues to voicing in word-final stop consonants: spectrographic and perceptual studies.

To determine durational differences between vowel and nasal segments preceding word-final /t/ and /d/, spectrograms were made of adult speakers' productions of minimal pairs of the type /pent/-/pend/. Vowel, nasal, and vowel plus nasal (vocalic nucleus) durations were greater before /d/ than before /t/. Assuming the voiceless context as a base, the increase in nasal duration in the voiced case was proportionately greater than the increase in vowel duration. This outcome suggests that nasal duration is a more powerful cue to the voicing characteristic of the following consonant than is vowel duration. To test this, adult listeners were presented synthetic CVNC utterances in which the nasal and vowel segments were independently varied in duration over a range of 40 msec to 200 msec and were instructed to label the final stop consonant as either voiced /d/ or voiceless /t/. Although changes in both vowel and nasal duration were sufficient to cue both voiced and voiceless judgements, listeners' categorization of final consonants shifted more rapidly as a result of varying nasal rather than vowel duration. Nasal duration, therefore, appears to be a stronger cue than vowel duration for the word-final voiced-voiceless consonant distinction in CVNC utterances.

Acoustics↗
PubMed1975

Perception of temporal order in vowel sequences with and without formant transitions.

Temporal-order perception of phoneme segments in running speech is much superior to temporal-order perception in repeating vowel sequences. The more rapid rates possible in running speech may be due largely to the presence of formant transitions. In a series of five experiments we observed that many temporal-order misjudgements of repeating vowels can be explained in terms of auditory stream segregation, triggered for the most part by discontinuities in first-formant frequencies of adjacent vowels. Streaming, however, can be suppressed by formant transitions appropriate for the perception of stop consonants and by continuous transitions resembling those in coarticulated vowels. At rapid sequence rates, when the constraints of auditory streaming are removed, correct temporal-order identification is limited by linguistic transformations of vowels into other phoneme segments.

Adolescent↗