Electroglottographic observations of young stutterers' fluency.

The purpose of this study was to compare the laryngeal behavior associated with the perceptually fluent speech of young stutterers (n = 8) to that of their normally fluent peers (n = 8). Laryngeal behavior during fluent productions of the initial and final consonants and medial vowels in each of the words Pete, bake, face, and veal was observed by means of an electroglottograph (EGG). The recorded EGG signal was electrically processed to obtain a measure of vocal fold abduction from the "open quotient" (glottal open time divided by glottal period) during consonant-vowel (CV) and vowel-consonant (VC) transitions, as well as during the central portion of the vowel. In each case, a Typical pattern for the abduction measure that was consistent with the underlying production mechanism for the sound sequence was found for the normally fluent subjects. The normally fluent children exhibited significantly more Typical patterns during the CV/CV transitions than did the stuttering youngsters, with 72% of the total transition samples from normally fluent youngsters being Typical versus 42% for the young stutterers. Though some Atypical patterns for the vowels were noted, most of the normally fluent (94%) and stuttering (84%) youngsters' total vowel samples were Typical. These findings suggest that some young stutterers tend to have difficulty stabilizing and controlling laryngeal gestures even during speech judged fluent by trained listeners, particularly at those points in the utterance where these youngsters must move between sound segments.

Encoding voice fundamental frequency into vibrotactile frequency.

Measured in this study was the ability of eight hearing and five deaf subjects to identify the stress pattern in a short sentence from the variation in voice fundamental frequency (F0), when presented aurally (for hearing subjects) and when transformed into vibrotactile pulse frequency. Various transformations from F0 to pulse frequency were tested in an attempt to determine an optimum transformation, the amount of F0 information that could be transmitted, and what the limitations in the tactile channel might be. The results indicated that a one- or two-octave reduction of F0 vibrotactile frequency (transmitting every second or third glottal pulse) might result in a significant ability to discriminate the intonation patterns associated with moderate-to-strong patterns of sentence stress in English. However, accurate reception of the details of the intonation pattern may require a slower than normal pronounciation because of an apparent temporal indeterminacy of about 200 ms in the perception of variations in vibrotactile frequency. A performance deficit noted for the two prelingually, profoundly deaf subjects with marginally discriminable encodings offers some support for our previous hypothesis that there is a natural association between auditory pitch and perceived vibrotactile frequency.