Deaf Talkers Research Articles

Perceptual evaluations of spectral and temporal modifications of deaf speech.

The perceptual effect of modifying speech produced by deaf talkers was investigated to discover the changes necessary for disordered speech to be judged normal. Recordings of passages read by three deaf talkers were used as material. For the first two experiments, a three-syllable word was extracted from the deaf talkers' passages and from a similar passage recorded by a hearing talker. Each of the deaf speech samples was paired with the normal speech sample to generate various continua that differed in the spectral and temporal modifications applied to them. Within each continuum, the individual stimuli varied in the shape of the spectrum envelope and were produced by linear interpolation of LPC analysis parameters between the deaf and normal speech end points. Results suggest that correcting the temporal component of deaf speech alone is not enough to make it sound normal. Spectral corrections that approximate about 70% of normal appear to be necessary for the deaf speech samples to be judged normal. A third experiment made use of a 10-syllable segment of speech in which the relative contributions of spectral and temporal adjustments were investigated. The general conclusion of these three experiments is that spectral adjustments are more important to perceptual judgments of normality than temporal adjustments.

The Establishment of Open Articulatory Postures by Deaf and Hearing Talkers

Previous researchers have proposed that prelingually deafened talkers do not displace the tongue body to establish vowel steady-state postures and displace the jaw excessively. The purpose of this investigation was to evaluate the opening gesture lingual displacement patterns of three deaf and two hearing adult talkers. Cinefluorography and x-ray microbeam data indicated that the deaf subjects displaced their tongue bodies during the opening gestures. However, their glossal movement trajectories were qualitatively dissimilar to those of the hearing subjects. Whereas the hearing subjects moved the tongue differently for different vowel contexts, the deaf subjects had similar trajectories for all contexts. The common trajectories suggest that some deaf talkers contract their tongue muscles such that the tongue body moves similarly for all vowels. The deaf subjects also appeared to have a less flexible tongue body during speech production than the hearing subjects. Means for quantifying and comparing the lingual behaviors of deaf and hearing talkers are considered.

Jaw and lip movements of deaf talkers producing utterances with known stress patterns

This investigation determined whether prelingually deaf talkers could correctly produce stressed and unstressed syllables across known changes in stress patterning and phonetic composition. Three deaf and three hearing adults spoke sets of homogeneous syllable strings with stress patterns that they could tap successfully with a finger. Strain gauge transduction of lower lip and jaw movement indicated that both deaf and hearing subjects produced different displacements and durations for the stressed and unstressed syllables, regardless of the stress pattern. Jaw movement did not become more variable with changes in phonetic composition of the syllables. The results show no evidence that motoric abilities (as assessed in lip and jaw movements) limit deaf talkers in producing desired stress patterns.

Perceptual judgments of modified deaf speech

The perceptual effects of modifying speech produced by deaf talkers were investigated to examine, in part, the changes necessary for disordered speech to be judged normal. Recordings of the rainbow passage produced by a number of deaf male speakers were studied and three passages judged to be moderately disordered were selected. The word “beautiful” was extracted from these passages and from a similar passage recorded by a hearing talker. Each of the deaf talkers' productions was paired with the normal production to make two types of continua. One type was based on a time warping of the disordered speech to fit the temporal structure of the normal speech, while the other was based on a time warping of the normal speech to the temporal structure of the disordered speech. Each continuum contained ten steps, ranging from disordered to normal spectral properties. Graduate students in the fields of speech and hearing judged whether the stimuli sounded normal or disordered. Continua based on the normal talker's...

The influence of final-syllable position on the vowel and word duration of deaf talkers.

Hearing talkers produce shorter vowel and word durations in multisyllabic contexts than in monosyllabic contexts. This investigation determined whether a similar effect occurs for deaf talkers, a population often characterized as lacking coarticulation in their speech. Four prelingually deafened adults and two hearing controls produced three sets of word sequences. Each set included a kernel word and six derived forms (e.g., "speed," "speedy," "speeding," etc.). The derived forms were created by adding unstressed and stressed syllables to the kernel form. A spectrographic analysis indicated that the deaf subjects did not always decrease word and vowel durations for the derivatives. Unlike hearing speakers, they often did not reduce vowel segments more than consonant segments. Three explanations are forwarded for the shortening effects. One relates to the implementation of temporal rules, the second concerns the organization imposed upon the articulators to produce speech, and the third suggests a language-independent vocal tract characteristic. The role of auditory information in developing the shortening effects is also considered.

Marking word boundaries to improve the intelligibility of the speech of the deaf.

Speech of deaf talkers has often been characterized as staccato, leading to the perception of improper grouping of syllables. In an attempt to compensate for this syllabication, word boundaries of 30 sentences spoken by 10 deaf children were acoustically marked by means of silent pauses with a duration of 160 ms inserted between words. Subsequent tests with normal-hearing listeners demonstrated that after insertion of pauses the intelligibility of the sentences increased significantly (p less than .01) from 27% to 31%. A control measure showed that this increase was not merely due to a general deceleration of speech rate: When all phonemes were lengthened until the same sentence duration was obtained as after insertion of pauses, a (nonsignificant) decrease in intelligibility (M = 26%) resulted. The results are compared to earlier studies of speech of the deaf in which segmental and suprasegmental aspects were manipulated.

Articulatory reorganization in deaf talkers

The ability of five intelligible deaf talkers to reorganize articulatory gestures was examined with the use of a bite block. Each subject produced the phrase “say a pVp again” (where V = [i, a, u, æ, ı] or [ɛ]), with 14 repetitions of each vowel in random order. The speech samples were obtained with and without the subjects wearing their hearing aids. Measures of VOT, vowel duration, F1, and F2 were obtained from wideband spectrograms. The speech of the two subjects with an early onset of deafness was affected by the presence of the bite block whereas the speech of the remaining three subjects, whose deafness occurred in adulthood, was not. Performance was similar for all subjects irrespective of whether they were wearing their hearing aids. The role of auditory information in the formative years of speech motor control is discussed. [Research supported by the Easter Seal Research Foundation and a Biomedical Research Support Grant from the NIH.]

Acoustic distinctions between intelligible and unintelligible vowels in the speech of the deaf

The purpose of this study was to determine if systematic differences in F1,F2, and duration distinguished intelligible and unintelligible vowels in the speech of the deaf. Five deaf speakers produced 35 tokens of selected vowels in CVC monosyllabic words. The intelligibility of the vowel was rated on a 1–5 scale by three listeners familiar with the speech of the deaf. Differences between the deaf speakers and a control group of speakers with normal hearing were noted in mean formant values and token‐to‐token variability in F1 and F2. These differences were present even in the most intelligible samples produced by the deaf subjects. In general, relatively large differences in F1 and F2 were present for intelligible and unintelligible productions in the speech of the deaf talkers. Further, token‐to‐token variability in F1 and F2 was greater for the unintelligible than the intelligible productions. There was, however, some overlap of the distribution of intelligible and unintelligible tokens, suggesting that other acoustic dimensions in addition to formant values contributed to perceived intelligibility. No obvious relationship between duration and intelligibility was noted. [Work supported in part by the Easter Seal Research Foundation.]

A usable test for the speech intelligibility of deaf talkers.

A strange fact about the contemporary education of the hearing-impaired is that the intelligibility of their speech is seldom measured. This paper describes an easy way to use an accurate test for the intelligibility of the speech of severely hearing-impaired speakers. The test is based upon the use of minimal pairs of words and requires no more than 30 minutes to administer. Data on the validity, reliability, and internal consistency of the test are presented to show that it can reliably predict the intelligibility of running speech.

A spectrographic investigation of consonant-vowel transitions in the speech of deaf adults

A spectrographic investigation was carried out on the speech of normal-hearing and deaf speakers; the research attempted to answer questions concerning formant transitions, coarticulation and neutralization of vowels in the speech of the deaf adults. Recordings were made of each subject reading a constant carrier phrase into which a changing medial monosyllable was embedded. The deaf subjects chosen for this investigation were judged to be above average in intelligibility (for deaf talkers that is); they exhibited a profound bilateral hearing loss of early onset. Wide band spectrograms were made of selected recorded stimulus items. The results indicated that the transitions of deaf speakers had a restricted range and slower rate of movement than did those of the normal talkers. Further, the speech of the deaf showed relatively few coarticulation effects, their vowel formants tended to be neutralized and they tended to begin any given articulatory sequence in a manner similar to any other regardless of context.

Comparison of intelligibility with duration and pitch control in the speech of deaf children

Two measurements of prosody were made from the connected speech of 37 hearing-impaired and six normally hearing adolescents: (1) average word duration, and (2) amount of variation in fundamental frequency. The intelligibility of the subjects was measured by scoring the performance of 50 normal listeners. A significant (negative) correlation was found between average word duration and intelligibility, and a slightly higher (also negative) correlation between the duration of function words and intelligibility. In contrast, linguistically appropriate pitch control, as measured by the amount of F0 variation, does not correlate with speech intelligibility. That is, the speech of both intelligible and highly unintelligible speakers may exhibit a large amount of F0 variation. The amount of F0 variation is probably an inadequate measure of pitch control, since it takes into account neither the appropriateness of F0 variation nor any of the following three deviations common among deaf talkers: (1) F0 quaver, (2) F0 discontinuity, and (3) diplophonia. [Supported by NINDS Grant NS 03856.]

Phonation characteristics: a comparison of normal hearing, deaf trained orally, and deaf trained in the Rochester Method

This paper is concerned with a quantitative description of the phonation characteristics of deaf talkers and the manner in which those characteristics differ as a function of the student's training background. A total of 40 deaf high school students (20 male and 20 female), ages 15–18, served as subjects. All subjects were prelingually deaf, with hearing losses of 90 dB or more in the better ear. Eighteen of the deaf subjects had received all of their formal speech training at the Clarke School for the Deaf, where only the oral method is used. Twenty-two deaf subjects had received all of their communication training at the Rochester School for the Deaf, where the method of combining fingerspelling and speech is used. An analogous group of normally hearing high school students was used for comparison. Speech samples were recorded as the subjects read a phonetically balanced paragraph. The high-quality speech recordings were digitalized and subsequently processed using a period-by-period computer analysis program. This method provided information about each subject's mean fundamental frequency, variability and skewness of the distribution, and phonation time ratio. The results are discussed both in terms of group performance and individual differences.

An Acoustic and Electromyographic Investigation of Consonant-Vowel Transitions in the Speech of Deaf Adults

An acoustic and electromyographic investigation of the speech of normal-hearing and deaf speakers attempted to answer questions concerning formant transitions, coarticulation, and neutralization of vowels in the speech of deaf adults. In order to accomplish this, EMG and acoustic recordings were made simultaneously as each subject read a constant phrase into which a variable key word was embedded. The deaf speakers chosen for this study were judged to be above average in intelligibility for deaf talkers with a profound bilateral hearing loss of early onset. Acoustical analysis was performed by making wide-band spectrograms of selected recorded stimulus items. The amplitude display of the sonograph was used for relating electromyographic events to acoustic events in time. The results of this study showed that the transitions of deaf speakers had a restricted range of movement and a slower rate of movement than those of normal speakers. The speech of the deaf shows relatively small coarticulation effects, their vowels tend to be neutralized regardless of the context, and they tend to begin an articulatory sequence in a similar manner regardless of the context. The deaf speakers also exhibited difficulty coordinating articulation with phonation and their articulatory behavior showed greater variability than did the articulatory behavior of the normal speakers. The discussion of the results will indicate their implications for speech training of the deaf.

An electromyographic study of consonant articulation in hearing-impaired and normal speakers.

The purpose of this study was to obtain comparative information on the articulation of some common consonants by a very small sample of normal and deaf talkers. Information on the organization of articulation was collected by electromyography. Electrodes were placed on some diagnostic locations on the facial and tongue musculature, and the patterns of contractions were measured for 11 common consonants spoken in a disyllabic frame. The results show that patterns of facial muscle contractions in the deaf speakers are in general correct, by comparison with normals, although they are generally exaggerated. On the other hand, tongue muscle patterns of the deaf speakers are stereotyped but frequently wrong, though there is no consistent pattern to the direction of the errors.