Accuracy and variability of acoustic measures of voicing onset

Five commonly used methods for determining the onset of voicing of syllable-initial stop consonants were compared. The speech and glottal activity of 16 native speakers of Cantonese with normal voice quality were investigated during the production of consonant vowel (CV) syllables in Cantonese. Syllables consisted of the initial consonants /ph/, /th/, /kh/, /p/, /t/, and /k/ followed by the vowel /a/. All syllables had a high level tone, and were all real words in Cantonese. Measurements of voicing onset were made based on the onset of periodicity in the acoustic waveform, and on spectrographic measures of the onset of a voicing bar (f0), the onset of the first formant (F1), second formant (F2), and third formant (F3). These measurements were then compared against the onset of glottal opening as determined by electroglottography. Both accuracy and variability of each measure were calculated. Results suggest that the presence of aspiration in a syllable decreased the accuracy and increased the variability of spectrogram-based measurements, but did not strongly affect measurements made from the acoustic waveform. Overall, the acoustic waveform provided the most accurate estimate of voicing onset; measurements made from the amplitude waveform were also the least variable of the five measures. These results can be explained as a consequence of differences in spectral tilt of the voicing source in breathy versus modal phonation. ©2003 Acoustical Society of America.published_or_final_versio

Timing and Intensity Variability in the Metronomic Speech of Stuttering and Nonstuttering Speakers

The timing and intensity variability of 8 adults who stutter and 8 age-matched fluent speakers was investigated under metronomic conditions. Participants were required to produce double or triple-stress patterns at a slow speech rate (1 syllable/870 ms) when repeating the syllable /stæt/ or /stræt/ nine times. Measures that are sensitive to cyclic rather than overall variation in syllable timing and intensity were employed. Specifically, durational variation between successive syllable onsets as well as intensity variation of the beginning consonant and vowel in successive syllables were computed. Results revealed that, although intensity variation was similar, the timing of successive syllables of persons who stutter was significantly more variable than that of persons who do not stutter. These outcomes are discussed in relation to previous experiments of timing control of persons who stutter and normally fluent persons during metronomic stimulation