Acoustic features of normal-hearing pre-term infant cry.

Acoustic features of expiratory cry vocalizations were studied in 125 pre-term infants prior to being discharged from a level-3 neonatal intensive care unit. The purpose was to describe various phonatory behaviors in infants in whom significant hearing loss could be ruled out. We also compared these results with normal-hearing full-term infants, and evaluated whether linkage exists among acoustic cry features and various anthropometric, diagnostic and treatment variables obtained throughout the peri- and neonatal periods. Our analysis revealed that cry duration was significantly related to total days receiving respiratory assistance. The occurrence of other complex spectral and temporal aspects of acoustic cry vocalizations including harmonic doubling and vibrato also increased in infants receiving some form of respiratory assistance. The presence of harmonic doubling also depended on weight and conceptional age at test. The discussion focuses on the implication of these relationships and directions for future research.

Inverse-filtered air flow and EGG measures for sustained vowels and syllables.

The purpose of this investigation was to compare the effects of two speaking tasks on laryngeal measures obtained from inverse-filtered air flow and electroglottograph (EGG) waveforms. Flow amplitude, air flow duty cycle, EGG duty cycle, and fundamental frequency were measured for normal young and aged adults during vowel prolongation and syllable repetition. There were significant between-task differences for flow amplitude and fundamental frequency. Variability appeared no greater for syllable repetition than vowel prolongations. Syllable repetition was slightly better than vowel prolongation for differentiating the vocal behaviors of aged and young speakers. Between-task relationships were strong for fundamental frequency and more moderate for the other laryngeal measures. It was concluded that syllable repetition would be preferable to vowel prolongation for measurement of aerodynamic and EGG parameters and that findings could be generalized across speaking tasks for fundamental frequency but not air flow and duty cycle measures.

A comparison of selected phonatory behaviors of healthy aged and young adults.

Selected phonatory behaviors of healthy aged and young men and women were compared. Inverse-filtered air flow, electroglottograph (EGG), and intraoral air pressure signals were recorded as subjects phonated in each of four conditions: normal, soft, loud, loud/high pitched. Minimum flow offset, flow amplitude, air flow duty cycle, EGG duty cycle, estimated subglottal pressure, and fundamental frequency were derived from the recorded signals and compared among age/gender groups. Males had significantly greater flow amplitude than females regardless of age. Significant Age x Sex interactions were found for fundamental frequency and duty cycle measures. Duty cycles and fundamental frequency increased for males and decreased for females with aging. For the normal phonatory condition, aged men had significantly greater duty cycle measures, flow amplitude, and estimated subglottal pressure than young men. There were significant differences in fundamental frequency and EGG duty cycle between aged and young women during normal phonation. It was concluded that the effects of aging on phonatory behaviors are different in degree and kind for men and women. Fewer significant age-related differences in phonatory measures for women than men were consistent with reports of less age-related laryngeal degeneration in females than males.

Syllable durations of preword and early word vocalizations.

The continuity in development of syllable duration patterns was examined in 7 young children as they progressed from preword to multiword periods of vocalization development. Using a combination of lexical and chronological age points, monthly vocalization samples were analyzed for bisyllable duration and final syllable lengthening. Results revealed no systematic increase or decrease in the duration of bisyllables produced by the children as a group. Lengthening of final syllables was observed across nearly all recording sessions for all children. It is likely that the feature of bisyllable duration is not discernibly sensitive to changes associated with a developing speech mechanism and environmental input. On the other hand, the regularity in final syllable lengthening is consistent with a continuity theory of development.

Acoustic validation of phonological knowledge and its relationship to treatment.

The speech of 4 phonologically disordered children with place and voicing errors affecting initial stop consonants was described through phonological and acoustic analyses. Productions of target voiced and voiceless alveolar and velar stops were transcribed and acoustically analyzed before and after treatment that was administered on a predetermined contrast. Three of the children produced significant, although largely imperceptible, differences in VOT for a given stop when it represented different adult stops. The presence of productive phonological knowledge, as inferred from acoustic data, facilitated rapid generalization of correct production of the treated contrast. In the absence of acoustically determined productive knowledge, a longer treatment period was necessary to achieve a lower level of production accuracy on the same treated contrast. Sources of speech sound errors for the 4 children were hypothesized by comparing the children's underlying representations determined from both acoustic and descriptive phonological data.

A comparison of intrasubject variation across sessions of three vocal frequency perturbation indices.

Within-subject variation of three vocal frequency perturbation indices was compared across multiple sessions. The magnitude of jitter factor (JF), pitch perturbation quotient (PPQ), and directional perturbation quotient (DPF) was measured every other day for 33 consecutive days for ten female and five male normal young adult speakers. Perturbation measures were calculated using a zero-crossing analysis of taped [i] and [u] productions. Pearson product-moment correlations among the three perturbation indices were calculated to examine their relation over time. Coefficients of variation for JF, PPQ, and DPF were considered indicative of the temporal stability of the three measures. JF and PPQ provided redundant information about laryngeal behaviors in steady-state productions. DPF, however, appeared to measure different laryngeal behaviors. Also, JF and PPQ varied considerably within individuals across sessions while DPF was the more temporally stable measure. Multiple sampling sessions and measurement of both the magnitude and direction of period differences are advised for future investigations of vocal frequency perturbation.

Vocal fundamental frequency characteristics during the first two years of life.

Vocal fundamental frequency (Fo) characteristics were sampled for a group of seven young children. The children were followed longitudinally for a 12-month period, spanning preword, single-word, and multiword vocalizations. The Fo characteristics were analyzed with reference to chronological age, vocalization length, and lexicon size. Measures of average Fo and Fo variability changed little during the 12-month period for each child. A rising-falling intonation contour was the most prevalent Fo contour among the children. In general, the influence of vocalization length and language acquisition on measures of Fo was negligible. It is suggested that relative uniformity in vocal Fo exists in early vocalizations across preword and meaningful speech periods.

Acoustic observations in young children's non-cry vocalizations.

A corpus of 1200 non-cry vocalization samples produced by 14 normal children between the ages of 11-25 months was examined retrospectively. Six percent of the samples yielded instances of either harmonic doubling (HD), fundamental frequency (F0) shift, or biphonation (Bp). These spectrographic features relate to short duration changes in F0, reflecting alterations in vocal fold state characteristics. The HD and Bp segments were perceptually judged to be harsh, while F0 shift closely reflected pitch breaks. The frequency of occurrence of the three acoustic features suggests that they are normally occurring phonatory events in normal children's vocal patterns.

Clinical application of two phonologically based treatment procedures.

Two phonological process-based treatment procedures were applied in an ongoing clinical program. Subjects were 4 children aged 3:1, 3:8, 4:1, and 5:1. Two subjects were assigned to a minimal pairs contrasting procedure, and 2 were assigned to a modified cycles procedure based on results of a detailed phonological analysis. All children demonstrated marked changes in their phonological systems as shown by the results of pretreatment and follow-up generalization probes. Correct production generalized to sounds affected by the treatment process that were not a focus of training. Correct production of untrained sounds lagged behind that of trained sounds for all subjects. Results support the hypothesis that articulation remediation is enhanced by treating phonological processes as well as the notion that the acquisition of phonology is a gradual process. Both treatment procedures used in this study were found to be effective and efficient, as evidenced by the elimination of up to three phonological processes within 2 1/2 months for each subject.

Developmental trends in vocal fundamental frequency of young children.

Fundamental frequency (F0) values are reported for 14 children between the ages of 11 and 25 months, an age period characterized by changes in physiological and linguistic development. Subjects were grouped into 3-month age intervals reflecting a continuum of physical development and were audiotape-recorded during spontaneous speech productions. Acoustic analysis of average F0 and F0 variability was performed. F0 variability was found to decrease as subject age increased, as did segment durations. The decrease in average F0 across the arbitrary age groups did not reach significance; however, when viewed within the overall developmental period and in comparison with data from other studies of younger and older children, average F0 during this age is consistent with a decreasing trend throughout early childhood.

A comparison of language samples elicited at home and in the clinic.

One of the most common methods of obtaining diagnostic information about a child's language production is to collect and analyze a spontaneous language sample. Usually, this sample is collected in a clinical setting by a speech-language pathologist. Because children's language production seems very sensitive to situational variables, there is some question about the representativeness of language samples obtained in clinical settings. This study compared language samples obtained in the home by the mothers with those obtained in the clinic by speech-language pathologists. Subjects were three- to five-year-old children who had been referred for speech and language diagnostics. Results were that the children's mean-length-of-utterance (MLU) scores were better for the home sample, although there was no difference between their Developmental Sentence Scores (DSS) for the home sample and the clinic sample. The home samples yielded higher MLU stage placements (Brown, 1973) and higher estimated language ages on the DSS (Lee, 1974) for most of the children. Clinical implications of the results are discussed.