Effects of environmental noise on computer-derived voice estimates from female speakers.

The purpose of this study was to examine the influence of noise on voice profile statistics from female samples. Six young adult females served as subjects. Five had normal voices; one had a pathological voice with accompanying bilateral vocal nodules. Each female subject was required to match a generated 235 Hz tone (+/- 2 Hz) while maintaining a constant output level of 70 dB SPL (+/- 5 dB). Data collected from a previous study involving a normal male subject were included for comparative purposes. Noise was generated from a personal computer fan which had a strong center frequency component at 235 Hz. Six different A-weighted signal-to-noise [S/N(A)] conditions were created, ranging in 5 dB increments from 25 to 0 dB. Results revealed that fundamental frequency was reasonably resistant to the effects of noise and to the effects of the noisy (pathological) voice signal. Jitter and shimmer estimates generally increased as noise floors elevated. The greatest amount of measurement error was found for the pathological female voice when captured in the presence of environmental noise. Findings are discussed relative to clinical issues surrounding measurement error.

Accuracy of jitter estimates using different filter settings on Visi-Pitch: a preliminary report.

Preliminary findings are presented regarding Visi-Pitch settings in relation to automatically derived perturbation values (jitter). Jitter values were estimated from sustained phonation of /a/ at each of four filter settings for three subjects using Visi-Pitch. Data were compared to values obtained by hand measuring the same signals and employing Koike's formula. Results indicated that the magnitude of difference between jitter estimated by Visi-Pitch and hand measurement was small. Findings support the use of the manufacturer's recommended filter settings as opposed to alternative settings suggested by Karnell.

A comparison of temporal measures of speech using spectrograms and digital oscillograms.

To determine whether any systematic differences occur as a result of using spectrograms versus digital oscillograms to make durational measurements, a number of temporal features (e.g., voice onset time, vowel duration, and consonant closure duration) for 3 speakers were independently measured by 2 different investigators. Both experimenters measured the same intervals with conventional spectrograms and with digital oscillograms, separated by at least a 2-week interval. Oscillograms tended to reveal slightly longer vowel durations and more voicing during consonant closure, while spectrograms evidenced slightly longer consonant closure durations. In general, variations between the two types of instrumentation were no more than 8 to 10 ms and are, therefore, of primary consequence only for studies in which quite small temporal differences are critical.

Perception of the voiced-voiceless contrast in syllable-final stops.

A computer editing technique was used to remove varying amounts of voicing from the syllable-final closure intervals of naturally produced tokens of /p epsilon b, p epsilon d, p epsilon g, pag, pig, pug/. Vowels for all six syllables were approximately the same duration, and the final release bursts were retained. Identification results showed that voiceless responses tended to occur in relatively large numbers when all of the closure voicing and, in most cases, a portion of the preceding vowel-to-consonant (VC) transition had been removed. A second experiment demonstrated that removal of final release bursts had very little effect on the identification functions. Acoustic measurements were made in an attempt to gain information about the acoustic bases of the listeners' voiced-voiceless judgments. In general, stimuli that subjects tended to identify as voiceless showed higher first-formant offset frequencies and shorter intensity decay times than stimuli that subjects tended to identify as voiced. However, for stops following /i/ and /u/ these acoustic differences were relatively small. We were unable to find a single acoustic measure, or any combination of measures, that clearly explained the listeners' voiced-voiceless decisions.

Cross-sectional study of gross and fine motor development. Birth to 6 years of age.

A total of 187 healthy children between birth and six years of age were administered a comprehensive gross and fine motor development assessment. The assessment device was a hybrid instrument consisting of 192 items derived from 15 commonly used instruments. The purpose of the study was to 1) define motor behavior relative to a performance distribution expressed in age ranges, 2) identify patterns of performance across a range from birth to 6 years of age, and 3) assess the stability of performance by comparing select tasks with norms available in the literature. Emergence and achievement levels of successful performance were defined for 37 items relative to 68 percent and 95 percent of the children across the range from birth to 6 years of age. These results were compared with eight assessment devices. Emergence comparisons were found to be fairly similar to published norms; achievement comparisons showed a higher frequency of discrepancies with published norms. Performance patterns were displayed graphically to illustrate symmetry and asymmetry in normal development milestones.

Phrase-level timing patterns in English: effects of emphatic stress location and speaking rate.

Phrase-level timing patterns in the utterance Bob hit the big dog were studied as a function of emphatic-stress location at two speaking rates. Five emphatic-stress conditions were defined: emphasis on each of the four content words, and one condition with no emphatic stress (neutral emphasis). Three subjects produced twenty repetitions of each condition at both rates. Results showed (1) the effect of emphatic stress on segment duration was not confined to the emphasized segments, but was manifest in nonemphasized segments as well; (2) when emphatic stress occurred near the beginning of the utterance, segment durations toward the end of the utterance were shortened relative to the duration of these segments in the neutral-emphasis utterance; however, for emphatic stress late in the utterance, beginning segments were not so modified; (3) the duration correlate of emphasis varied with position-in-utterance; and (4) increased speaking rate reduced or eliminated timing contrasts observed at the conversational rate, and affected the utterance-final segment differently from segments in other utterance positions.