Word length effects on EMG/vowel duration relationships in apraxic speakers.

The effects of word length on the timing of lip electromyographic (EMG) activity for production of the vowel /u/ and the relationship of this activity to vowel duration were examined in matched male and female pairs of normal and apraxic speakers. Both apraxic speakers had suffered left cerebrovascular accidents, which resulted in apraxia of speech as the primary communication deficit. For all participants, the interval of time in which lip muscle activity was present prior to the onset of voicing for the /u/ (EMG onset interval) in each word systematically decreased as word length increased. However, EMG activity offset intervals, which were measured from the onset of voicing for /u/ to the onset of the reduction of EMG activity during the vowel (EMG termination interval), decreased as word length increased only for the normal speakers. Relative onset of EMG activity was not significantly related to relative offset of EMG activity or relative vowel duration. However, the relative EMG onset interval was correlated with the duration of an entire word. Findings for the relative EMG termination interval were variable and are discussed relative to the severity of apraxia of speech.

Lip EMG activity during vowel production in apraxia of speech: phrase context and word length effects.

This investigation examined the timing relationships of EMG activity underlying vowel production in 2 normal individuals and in 2 individuals with marked-to-severe apraxia of speech of approximately two-and-one-half years duration. The timing of lip muscle activity was investigated in monosyllabic words embedded in phrases and in syllable word stems as a function of changes in word length. Specifically, the onset and offset of EMG activity of lip muscles used for production of /u/ in the monosyllables and word stems were examined. The results revealed that the relative amounts of time devoted to onset and offset of EMG activity for lip rounding are disorganized in apraxia of speech. Word length appeared to affect the timing of the onset of muscle activity for both the normal speakers and the speakers with apraxia of speech. Word length also influenced the offset of muscle activity, but its effect was less systematic for the speakers with apraxia of speech. The findings suggest that termination of EMG activity may be at least as disturbed as the initiation of EMG activity in apraxia of speech.

Speech breathing in senescent and younger women during oral reading.

Breathing patterns in 20-30-year-old and 60-70-year-old women were recorded noninvasively during various nonspeech and oral reading tasks. On the nonspeech tasks, the only significant difference between groups was a smaller mean vital capacity for the older women. On oral reading, the older women had significantly greater means for absolute and relative inhalatory volumes, relative inhalatory airflow rates, absolute and relative volumes during nonphonatory exhalations, and relative exhalatory volumes. No significant mean differences between groups were found on absolute inhalatory airflow rates, absolute exhalatory volumes during speech, and absolute and relative exhalatory airflow rates. In both age groups, increases in sentence length were associated with significantly increased inhalatory and exhalatory volumes but mean airflow rates were not significantly affected by sentence length. Some differential effects of reading context on only the older group seemed to represent additional demands placed on their respiratory systems for speech breathing.

Voice onset time in young and 70-year-old women.

This study was conducted to determine the effect of aging on voice onset time (VOT). Ten women between 20 and 30 years old and 10 women between 70 and 80 years old read CVC syllables embedded in a carrier phrase. Spectrograms were used to measure VOT for voiced and voiceless bilabial and velar stops in the context of high and low vowels. Findings revealed that VOT was generally the same in older and younger subjects, and both age groups maintained similar voiced/voiceless and bilabial/velar distinctions. Older subjects demonstrated significantly shorter VOTs only in certain contexts involving place of consonant production and vowel context. The effects of aging on VOT, therefore, seem to appear only in selected phonetic contexts.

Relationships of vowel characteristics to listener ratings of breathiness.

This experiment was designed to investigate the relationships of listener ratings of breathiness to vowel duration, speaking rate, and the relative energy in three frequency ranges (100-500, 1500-2500, and 3500-4500 Hz) in vowel spectra. The effects of vowel SPL also were considered. Listeners used a seven-point equal-appearing interval scale to rate a sentence spoken by each of 10 young adult females in each of four voice qualities: normal speech, mildly breathy, severely breathy, and whisper. Significant Pearson correlations to the ratings were found only for mean SPL and the relative energy in the 100-500 and 3500-4500 Hz ranges. After the effects of mean SPL were accounted for in partial correlation and multiple regression analyses, all vowel parameters were related significantly to the mean ratings. The partial correlations for vowel duration were as high as those for the three frequency ranges. Vowel duration may be as important as spectral characteristics of vowels when breathiness is judged from samples of connected discourse.

Spectrographic study of vowels in stutterers' fluent speech.

Measurements were made of the formant frequencies and formant transitions associated with the vowels /i/, /ae/ and /u/ produced by seven moderate-to-severe stutterers when they read fluently in a control (normal) condition and under four experimental condition: masking noise, delayed auditory feedback, rhythmic pacing, and whispering. The first and second formant frequencies in an isolated /hVd/ context were more centralized than those reported for nonstutterers. The formant frequencies were centralized even more in reading, but varied little across conditions despite changes in fluency, speaking rates, and vowel duration. Duration and rate of formant transitions also were essentially the same across conditions. These findings and those reported in other studies indicate that stutterers' vowel production is more restricted, spatially and temporally, than nonstutterers'.

Syntactic and phonological influences on children's articulation.

The effects of syntactic and phonological structure on the consonant articulations of children with phonological deficits were investigated. Three structural variables were studied: syntactic structure (noun phrase, declarative sentence and passive sentence), work structure (monosyllable and disyllable) and word position (initial and final). Syntactic structure and word structure significantly affected the accuracy of articulation and the degree of word simplification. Structural complexity may contribute to overall hierarchial complexity, in turn causing children to simplify their speech.

Articulatory and phonological aspects of consonant substitutions in apraxia of speech.

The articulatory and distinctive features in 825 consonant substitutions produced by nine subjects with apraxia of speech were analyzed. The articulatory and distinctive features of the target consonants were retained beyond chance levels. The substitution patterns observed were very systematic in that more substitutions were made in the initial word position and stops, alveolars, and voiced consonants were used most often as substitutes for target consonants. The retention and usage of the features in the substitutions were closely related to the phonological markedness of the features, Most of the markedness changes were from marked-to-unmarked. The relationships between distinctive features and their markedness suggest that apraxia of speech is primarily a phonological disorder that is manifested in articulatoriy changes. It appears therefore that speakers with apraxia of speech systematically reduce linguistic complexity and simplify the production of consonants. In addition, the substitutions made in apraxia of speech are similar to those made by children.

Syntax influences the accuracy of consonant production in language-disordered children.

Nine children with restricted syntactic and phonological development repeated 20 target consonants embbedded in noun phrase, simple declarative, and passive structures to determine the influence of syntactic complexity on accuracy of consonant production. The children made significantly more errors in the sentence contexts than in the noun phrase context. This was found for both early-developing and late-developing consonants. However, the ratio of the number of distinctive feature modifications to the number of consonant errors showed that segmental errors were not produced as less exact approximations of the target consonants. Instead, the children simply made more errors of a predictable type, suggesting that the effect of syntax on accuracy of consonant production is quantitative rather than qualitative.