Previous investigators have shown that vowel duration decreases as the number of syllables in a word increases, when carrier phrases constitute the material. Umeda [J. Acoust. Soc. Am. 52, 133(A) (1972)] found that, in connected text, factors other than the number of syllables in the word have stronger influence in vowel duration. It turned out that differences were very small, if present at all, in vowel duration in connected text material. This investigation was conducted to find whether the differences result from speakers' idiosyncracies or from different speech modes—carrier phrase reading and connected speech. Two subjects, one of whom served in Umeda's study, read lists of monosyllabic and polysyllabic words in carrier phrases. Measurements were taken on the duration of one vowel /æ/, in stressed syllables in words of varying length. Conditions also investigated were the position of the stressed syllable and the class of the following consonant. Analyses of variance were computed separately for each subject. Results from the carrier sentence material confirm previous findings of the decreased duration, at least up to three syllables. One subject, while showing the characteristic shortening in vowel duration in the carrier phrase mode, exhibited almost no differences in duration of the vowel in connected text. Apparently the dependence of vowel duration on number of syllables is one of the dominating factors in the carrier phrase mode, but is a negligible factor in connected speech.
Difference limens (DLs) for fundamental frequency (F0) of naturally spoken sentences were studied. The experiments can be classified into two major categories. In the first category the fundamental frequency of a portion of sentences of 2 to 3 s in duration was manipulated. The second set of experiments used very short sentences (‘‘The subject verb’’) in which the F0 of the entire sentence was manipulated. Across experiments, sentences of comparable length yielded similar DLs, except when the F0 was abruptly shifted within a continuous voicing period. However, the DLs did vary significantly as a function of stimulus complexity and speaker. The range of DLs obtained in this series of experiments was between 10 and 50 times greater than that found with sustained synthetic vowels.
Groups of men were exposed for a 24-h period to either 70-Hz tones at 112.8±10 dB re 0.0002 dyn/cm2 or 300-Hz tones at 113.4±3 dB re 0.0002 dyn/cm2. During the exposure, performance on a sensory-motor task (“RATER”) was tested periodically, and auditory threshold shifts were measured. No decrement in RATER performance was noted for either group. TTSs were moderate except for one subject. The general behavior of the groups and statements made during informal interviews indicated that similar exposure conditions would be well tolerated on a routine basis.
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