Sentence intonation and syllable stress in speech produced during simultaneous communication.

This study investigated prosodic variables of syllable stress and intonation contours in contextual speech produced during simultaneous communication (SC). Ten normal-hearing, experienced sign language users were recorded under SC and speech only (SO) conditions speaking a set of sentences containing stressed versus unstressed versions of the same syllables and a set of sentences containing interrogative versus declarative versions of the same words. Results indicated longer sentence durations for SC than SO for all speech materials. Vowel duration and fundamental frequency differences between stressed and unstressed syllables as well as intonation contour differences between declarative and interrogative sentences were essentially the same in both SC and SO conditions. The conclusion that prosodic rules were not violated in SC is consistent with previous research indicating that temporal alterations produced by simultaneous communication do not involve violations of other temporal rules of English speech.

Effect of vowel environment on consonant duration: an extension of normative data to adult contextual speech.

In this study, we investigated the effect of vowel environment on consonant duration in contextual speech produced by adults. Previous studies, such as Schwartz's published in 1969 and DiSimoni's in 1974, of vowel influence on consonant duration have supported the notion of anticipatory scanning in which final vowel targets influence the duration of preceding fricative consonants. These studies were based on repetitions of nonsense syllables by children and adults, but no research has been reported that extends these data to contextual speech or examines speaker gender differences. Forty adult normal speakers (20 women and 20 men) recorded palatal and alveolar fricatives produced in four vowel environments in words embedded in contextual sentences. Results indicated significant effects of vowel context on consonant duration in contextual speech and revealed anticipatory scanning effects that are similar to those seen with nonsense syllables in previous studies. These normative data can form the basis for comparison of the effects of temporal alterations produced by speaking conditions such as simultaneous communication.

Effect of vowel environment on fricative consonant duration in speech produced during simultaneous communication.

This study investigated the effect of vowel environment on fricative consonant duration in contextual speech produced during simultaneous communication (SC). Previous studies (Schwartz, 1969) of vowel influences on consonant duration supported the notion of anticipatory scanning, in which final vowel targets influence the duration of preceding fricative consonants. Ten normal-hearing, experienced sign language users recorded palatal and alveolar fricatives produced in four vowel environments in contextual sentences under SC and speech-only (SO) conditions. Results indicated longer sentence durations for SC than for SO, and significant effects of vowel context on fricative consonant duration in contextual speech in both SC and SO conditions that revealed similar anticipatory scanning effects as seen in previous studies. These data confirm previous research indicating that the temporal alterations produced by simultaneous communication do not involve violations of the temporal rules of English speech.

Temporal characteristics of speech produced by inexperienced signers during simultaneous communication.

This study investigated temporal characteristics of speech produced during simultaneous communication (SC) by inexperienced signers. Recordings of stimulus words embedded in sentences produced with speech-only versus SC were made by 12 students during the first and last weeks of an introductory sign language course. Results indicated significant temporal differences between speech-only and SC conditions during both the first week and the last week of the class. Inexperienced signers appeared to sign between words in SC during the first week of the class, thereby extending interword intervals. At the last week of the class, they appeared to shift toward simultaneously signing while producing the words, thereby elongating segmental temporal characteristics, such as vowel duration. The specific temporal differences between SC and speech-only conditions were consistent with previous findings regarding the effect of SC on temporal characteristics of speech with experienced signers.

Voice onset time in speech produced by inexperienced signers during simultaneous communication.

This study investigated sentence duration and voice onset time (VOT) of plosive consonants in words produced during simultaneous communication (SC) by inexperienced signers. Stimulus words embedded in a sentence were produced with speech only and produced with SC by 12 inexperienced sign language users during the first and last weeks of an introductory sign language course. Results indicated significant differences between the speech and SC conditions in sentence duration and VOT of initial plosives at both the beginning and the end of the class. Voiced/voiceless VOT contrasts were enhanced in SC but followed English voicing rules and varied appropriately with place of articulation. These results are consistent with previous findings regarding the influence of rate changes on the temporal fine structure of speech (Miller, 1987) and were similar to the voicing contrast results reported for clear speech by Picheny, Durlach, and Braida (1986) and for experienced signers using SC by Schiavetti, Whitehead, Metz, Whitehead, and Mignerey (1996).

Production and perception of final consonant voicing in speech produced by inexperienced signers during simultaneous communication.

Simultaneous communications combines both spoken and manual modes to produce each word of an utterance. This study investigated the potential influence of alterations in the temporal structure of speech produced by inexperienced signers during simultaneous communication on the perception of final consonant voicing. Inexperienced signers recorded words that differed only in the voicing characteristic of the final consonant under two conditions: (1) speech alone and (2) simultaneous communication. The words were subsequently digitally edited to remove the final consonant and played to 20 listeners who, in a forced-choice paradigm, circled the word they thought they heard. Results indicated that accurate perception of final consonant voicing was not impaired by changes in the temporal structure of speech that accompanied the inexperienced signers' simultaneous communication.

Effect of fingerspelling task on temporal characteristics and perceived naturalness of speech in simultaneous communication.

This study investigated the effect of fingerspelling task length on temporal characteristics and perceived naturalness of speech produced during simultaneous communication. Stimulus words at four levels of fingerspelling task length were embedded in a sentence that was spoken and produced with simultaneous communication. Five temporal measures were calculated from acoustic recordings, and perceived speech naturalness was rated by a panel of listeners using a 9-point scale. Results indicated significant differences in temporal measures and naturalness ratings between the speech and simultaneous communication conditions and among levels of fingerspelling task length. Speech produced during simultaneous communication was rated as less natural and demonstrated increased interword interval, diphthong, word, and sentence durations. Regression analysis indicated significant correlations between temporal measures and perceived speech naturalness, and analysis of variance showed significant increases in segmental and interword interval durations and perceived speech unnaturalness as fingerspelling task length increased. These results are discussed in relation to previous findings regarding production and perception characteristics of speech that is altered in temporal parameters by a variety of conditions.

Effect of sign task on speech timing in simultaneous communication.

The purpose of this investigation was to study the effect of the signing task on temporal features of speech during simultaneous communication (SC). The effects of three independent variables: (a) communication mode (speech only vs. SC); (b) sign task demand (base vs. elaborated signs); and (c) type of sign movement (kinetic vs. morphokinetic) were studied on five dependent variables: (a) word duration; (b) sentence duration; (c) diphthong duration; (d) interword interval before signed experimental word (IWIB); and (e) interword interval after signed experimental word (IWIA). Audio recordings were made of 12 normal hearing, experienced sign language users speaking experimental words that varied in sign task demand and movement under SC and speech only (SO) conditions. Results indicated longer sentence durations for SC than SO and longer anticipatory durations of IWIB and diphthong before signed words, especially those using signs with greater task demand or with movements including hand shape change. IWIA only lengthened for SC vs. SO with no further effect of sign task demand or movement. These results indicate finite effects of sign task demand and movement on pause and segment durations before the sign but not as strong an effect as has been reported for increased finger spelling task length.

Production and perception of final consonant voicing in speech during simultaneous communication.

Simultaneous communication combines both spoken and manual modes to produce each word of an utterance. This study investigated the potential influence of alterations in the temporal structure of speech produced during simultaneous communication on the perception of final consonant voicing. Experienced signers recorded words that differed only in the voicing characteristic of the final consonant under two conditions: (a) speech alone and (b) simultaneous communication. The words were digitally edited to remove the final consonant and played to 20 listeners who, in a forced-choice paradigm, circled the word they thought they heard. Results indicated that accurate perception of final consonant voicing was not impaired by changes in the temporal structure of speech that accompany simultaneous communication.

Criterion validity of the Language Background Questionnaire: a self-assessment instrument.

The present investigation examined relationships between the Language Background Questionnaire (LBQ) self-assessed sign language skills. LBQ self-assessed spoken communication skills, and formal independent sign and spoken communication skills assessments of young adults who are deaf or hard of hearing. Results indicated a high degree of congruence between self-assessed communication skills and formal independent assessments of communication skills. The findings establish reasonable criterion validity for the LBQ regarding self-assessed sign language and spoken communication skills.

Voice onset time in speech produced during simultaneous communication.

This study investigated speaking rate and voice onset time (VOT) in speech produced during simultaneous communication (SC) by speakers with normal hearing. Stimulus words initiated with voiced and voiceless plosives were embedded in a sentence that was spoken and produced with SC. VOT measures were calculated from acoustic recordings and results indicated significant differences between speech-only and SC conditions, with speech produced during SC demonstrating both slower speaking rate and increased VOT of voiceless consonants. VOTs produced during both SC and speech-only conditions followed English voicing rules and varied appropriately with place of articulation. The somewhat enlarged voicing contrast during SC was consistent with previous findings regarding the influence of rate changes on the temporal fine structure of speech (Miller, 1987) and was similar to the voicing contrast results reported for clear speech by Picheny, Durlach, and Braida (1986).

Temporal characteristics of speech in simultaneous communication.

The purpose of this investigation was twofold: (a) to determine if there are changes in specific temporal characteristics of speech that occur during simultaneous communication, and (b) to determine if known temporal rules of spoken English are disrupted during simultaneous communication. Ten speakers uttered sentences consisting of a carrier phrase and experimental CVC words under conditions of: (a) speech, (b) speech combined with signed English, and (c) speech combined with signed English for every word except the CVC word that was fingerspelled. The temporal features investigated included: (a) sentence duration, (b) experimental CVC word duration, (c) vowel duration in experimental CVC words, (d) pause duration before and after experimental CVC words, and (e) consonantal effects on vowel duration. Results indicated that for all durational measures, the speech/sign/fingerspelling condition was longest, followed by the speech/sign condition, with the speech condition being shortest: It was also found that for all three speaking conditions, vowels were longer in duration when preceding voiced consonants than vowels preceding their voiceless cognates, and that a low vowel was longer in duration than a high vowel. These findings indicate that speakers consistently reduced their rate of speech when using simultaneous communication, but did not violate these specific temporal rules of English important for consonant and vowel perception.

Psychophysical analysis of audiovisual judgments of speech naturalness of nonstutterers and stutterers.

The purpose of this study was to determine through psychophysical comparison of scaling data whether speech naturalness judgments of stutterers and nonstutterers from audiovisual recordings form a prothetic or a metathetic continuum. Comparison of direct magnitude estimation and equal-appearing interval scale data indicated that speech naturalness forms a metathetic continuum when observers judge audiovisual recordings, suggesting that either scaling procedure is valid for the quantification of this dimension. Ease of use, an existing body of comparative data from different clinics, and somewhat better reliability favor the interval scaling procedure.

The use of artificial neural networks to estimate speech intelligibility from acoustic variables: a preliminary analysis.

Previous research has used regression analysis to attempt to predict the intelligibility of hearing-impaired speakers from acoustic speech parameters. Improvement of prediction may be achieved by the use of computerized artificial neural networks to process mathematically the acoustic input variables as part of the intelligibility process. A preliminary scheme for estimating speech intelligibility from acoustic parameters using a neural network is outlined and preliminary data illustrate its use.

Acoustic dimensions of hearing-impaired speakers' intelligibility: segmental and suprasegmental characteristics.

Regression and principal components analyses were employed to study the relationship between 28 segmental and suprasegmental acoustic parameters of speech production and measures of speech intelligibility for 40 severely to profoundly hearing-impaired persons in an effort to extend the findings of Metz, Samar, Schiavetti, Sitler, and Whitehead (1985). The principal components analysis derived six factors that accounted for 59% of the variance in the original 28 parameters. Consistent with the findings of Metz et al., a subsequent regression analysis using these six factors as predictor variables revealed two factors with strong predictive relationships to speech intelligibility. One factor primarily reflected segmental production processes related to the temporal and spatial differentiation of phonemes, whereas the other primarily reflected suprasegmental production processes associated with contrastive stress. However, the predictive capability of the present factor structure was somewhat reduced relative to the findings of Metz et al. (1985). Data presented indicate that the populations sampled in the two studies may have differed on one or more dimensions of subject characteristics. Considered collectively, the present findings and the findings of Metz et al. support the tractability of employing selected acoustic variables for the estimation of speech intelligibility.

Acoustic and psychophysical dimensions of the perceived speech naturalness of nonstutterers and posttreatment stutterers.

The purpose of this study was twofold: to determine through psychophysical comparison of scaling data whether speech naturalness is a prothetic or a metathetic continuum, and to examine the relationship between selected acoustic characteristics of the speech of nonstutterers and treated stutterers and listeners' judgments of their speech naturalness. Comparison of magnitude estimation and interval scaling data indicated that speech naturalness behaves like a metathetic continuum, suggesting that either scaling procedure is valid for the quantification of this dimension. The speech of the nonstutterers was judged more natural than the speech of the treated stutterers, and a global voice onset time (VOT) measure (averaged across places of articulation) and a sentence duration measure were found to be the acoustic parameters most highly correlated with and predictive of speech naturalness. These results suggest the possibility that stuttering treatments that employ strategies like gentle voicing onset and prolonged speech may result in somewhat slower posttherapy speech patterns characterized by prolonged VOTs that could influence listeners to judge the speech as more unnatural than the speech of nonstutterers.

Articulatory dimensions of hearing-impaired speakers' intelligibility: evidence from a time-related aerodynamic, acoustic, and electroglottographic study.

Regression and principal components analyses were employed to study the relationship between 30 aerodynamic speech parameters and the speech intelligibility of 40 severely to profoundly hearing-impaired speakers. Regression analysis on the original 30 aerodynamic variables revealed that speech intelligibility was predicted by a cognate-pair voice onset-time difference measure and a measure of the stability of the volume-velocity rise time. Principal components analysis of the 30 independent variables derived seven factors that accounted for 84.3% of the variance in the original 30 parameters. Subsequent regression analysis using the seven factors as predictor variables revealed four factors with independent relationships to speech intelligibility. These included a factor that reflected cognate-pair voice onset-time distinctions, a factor that reflected cognate-pair peak volume-velocity distinctions, and two other factors, which reflected production stability of temporal distinctions between cognate pair members.

Comparison of period-by-period fundamental frequency of stutterers and nonstutterers over repeated utterances.

The fundamental frequency (f phi) of the first five periods in the acoustic wave form of vowels following stop consonant productions and the f phi of a period approximately 100 ms into the vowel were analyzed in the repeated fluent utterances of 10 nonstutterers and 10 stutterers both pre- and posttherapy. Group data indicate that the nonstutterers and stutterers showed similar f phi diminution patterns in vowels immediately following stop consonants. Additionally, the stutterers were not significantly different from the nonstutterers in their ability to achieve a stable f phi over repeated utterances. These results are discussed with respect to a previous analysis of the present data (Sacco & Metz, 1986) in which it was found that stutterers were significantly more variable than nonstutterers in their ability to achieve a stable f phi over repeated utterances. It is suggested that stutterings in the immediate vicinity of otherwise fluently produced words may influence certain production characteristics of those words.

A cognitive/experiential approach to aural rehabilitation.

This paper describes an experiential speechreading course that was designed to provide hearing-impaired students with real-life communication experiences. The course, intended to function as a supplement to traditional speechreading courses, was evaluated with a self-evaluation questionnaire completed by students who took the course and by a matched control group. Results indicate that the course was effective in increasing student self-perceptions of communication success in real-life situations.

Criterion validity of speech intelligibility rating-scale procedures for the hearing-impaired population.

The criterion validity and reliability of two popular rating-scale procedures for the assessment of the contextual speech intelligibility of hearing-impaired individuals (The NTID Scales) were studied under clinically typical conditions of test administration and evaluation. The criterion measure was a write-down procedure based on subjects' readings of sentence lists chosen from The CID Everyday Sentence lists. Although the results revealed generally high overall validity and reliability coefficients for the two scales, a close examination of the distribution of estimation error over the full range of rating-scale values revealed gross violations of measurement prediction within the clinically most frequent midrange of speech intelligibility. The results indicate that the rating-scale procedure significantly compromises clinical and research classification of an individual's speech intelligibility and that write-down procedures may provide a viable and significantly more accurate alternative for speech intelligibility assessment.