Biomedical subjects

L Max

Publications and source records attributed to L Max.

9 recordsLinked to original sources

PubMed2005

Indication of a Lombard vocal response in the St. Lawrence River Beluga.

Noise pollution is recognized as a potential danger to marine mammals in general, and to the St. Lawrence beluga in particular. One method of determining the impacts of noise on an animal's communication is to observe a natural and repeatable response of the vocal system to variations in noise level. This is accomplished by observing intensity changes in animal vocalizations in response to environmental noise. One such response observed in humans, songbirds, and some primates is the Lombard vocal response. This response represents a vocal system reaction manifested by changes in vocalization level in direct response to changes in the noise field. In this research, a population of belugas in the St. Lawrence River Estuary was tested to determine whether a Lombard response existed by using hidden Markhov-classified vocalizations as targets for acoustical analyses. Correlation and regression analyses of signals and noise indicated that the phenomenon does exist. Further, results of human subjects experiments [Egan, J. J. (1966), Ph.D. dissertation; Scheifele, P. M. (2003), Ph.D. dissertation], along with previously reported data from other animal species, are similar to those exhibited by the belugas. Overall, findings suggest that typical noise levels in the St. Lawrence River Estuary have a detectable effect on the communication of the beluga.

Animal Communication↗

PubMed1999

Some issues in the statistical analysis of completely randomized and repeated measures designs for speech, language, and hearing research.

Contemporary investigators in the areas of speech, language, and hearing rely heavily on inferential statistical procedures to answer both basic and applied research questions. Such statistical procedures typically involve a number of assumptions that need to be fulfilled in order for the procedure to be appropriate for a specific data set. Unfortunately, a review of recent publications in the Journal of Speech, Language, and Hearing Research indicated that some pivotal issues related to those underlying assumptions, although widely discussed and emphasized in the statistical literature, often appear to be neglected in these fields of research. This tutorial therefore addresses two issues that are particularly important for an appropriate and accurate use of some of the most commonly used statistical procedures. The first issue concerns the importance of addressing the sphericity assumption in studies with a repeated measures design. The second issue concerns the definition of the experimental units in a statistical analysis and applies to both completely randomized and repeated measures designs. Theoretical aspects associated with each issue are discussed, and appropriate strategies for data entry and analysis are presented.

Hearing↗

PubMed1998

Adaptation of stuttering frequency during repeated readings: associated changes in acoustic parameters of perceptually fluent speech.

This study is part of a series investigating the hypothesis that stuttering adaptation is a result of motor learning. Previous investigations indicate that nonspeech motor learning typically is associated with an increase in speed of performance. Previous investigations of stuttering, on the other hand, indicate that improvements in fluency during most fluency-enhancing conditions or after stuttering treatment tend to be associated with decreased speech rate, increased duration of specific acoustic segments, and decreased vowel duration variability. The present acoustic findings, obtained from 8 individuals who stutter, reveal that speech adjustments occurring during adaptation differ from those reported for other fluency-enhancing conditions or stuttering treatment. Instead, the observed changes are consistent with those occurring during skill improvements for nonspeech motor tasks and, thus, with a motor learning hypothesis of stuttering adaptation. During the last of 6 repeated readings, a statistically significant increase in articulation rate was observed, together with a decrease in word duration, vowel duration, and consonant-vowel (CV) transition extent. Other adjustments showing relatively consistent trends across individual subjects included decreased CV transition rate and duration, and increased variability of both CV transition extent and vowel duration.

Adolescent↗

PubMed1997

Acoustic measures of temporal intervals across speaking rates: variability of syllable- and phrase-level relative timing.

It has been suggested previously that at least some levels of the temporal organization for speech production are characterized by proportional timing. The proportional timing model maintains that the duration of temporal intervals within a sequence would remain proportionally invariant across changes in overall duration of the sequence. In order to test this hypothesis for the acoustic level of speech production, 18 women produced three trials of the utterance "Buy Bobby a poppy" at each of three speaking rates (i.e., slow, normal, fast). Acoustically derived temporal intervals were paired to form ratios reflecting either syllable-level or phrase-level relative timing. Findings indicated that ratios of temporal intervals at both the syllable-level and phrase-level did not remain invariant across speaking rates. Rather, statistically significant changes in the relative duration of both types of intervals were observed as a function of overall rate of production. For most of the obtained ratios, the direction of these changes was highly consistent across individual subjects.

Adult↗

PubMed1997

Age-related effects on speech fluency.

This article provides a brief review of age-related changes in speech production before discussing fluency changes that have been found in aging, nonstuttering speakers. Most studies agree that old and young adults evidence similar frequencies of disfluency. The disfluencies of a 105-year-old woman were compared to the means of several geriatric groups whose average ages were more than 20 years younger. Overall frequencies and types were similar. Thus, aging speakers' fluency does not appear to be more susceptible to breakdowns than that of younger speakers, although there is some evidence that elderly speakers become much more disfluent than younger speakers under stressful conditions.

Adult↗

PubMed1997

Effects of aging on neuromotor processes of swallowing.

Isolated swallowing difficulties are present in a substantial percentage of elderly adults. Most have no known medical basis, although some may be caused by underlying, but undetected, medical conditions. Others may result from conditions that indirectly affect swallowing. After an overview of the neuroanatomy and neurophysiology of swallowing, this article reviews findings on changes in swallowing that accompany aging. Some of the differences reported have failed to be replicated consistently, and other changes are subtle, their significance unknown. Most studies, however, have found decreased sensitivity in both the oral and pharyngeal cavities. It is concluded that additional objective clinical measures are needed to isolate changes in swallowing due to age from those resulting from other causes. Clearly, further research is needed.

Adult↗

PubMed1997

Intelligibility of oesophageal and tracheo-oesophageal speech: preliminary observations.

The purpose of this study was to compare the intelligibility of two types of alaryngeal speech commonly used after total laryngectomy. Four male oesophageal speakers and four male tracheo-oesophageal speakers read a series of monosyllabic words, multisyllabic words and sentences. The monosyllabic word list consisted of several minimal pairs for each of eight phonetic contrasts; multisyllabic words and sentences were not selected on specific phonetic grounds. Audio recordings of all subjects' readings were presented to eight naïve adult listeners who completed both an item identification task and a scaling procedure. The item identification task revealed higher intelligibility fpr tracheo-oesophageal speakers than for oesophageal speakers during the monosyllabic word condition. Results from the scaling procedure indicated that listeners' subjective intelligibility ratings were also higher for the tracheo-oesophageal speakers than for the oesophageal speakers. Moreover, a high positive correlation was found between the speakers' intelligibility scores obtained from the word identification task and the scaling procedure.

Aged↗

PubMed1996

Speaking Fo and cepstral periodicity analysis of conversational speech in a 105-year-old woman: variability of aging effects.

We investigated speaking fundamental frequency and periodicity of voicing during conversational speech in a 105-year-old woman. Analyses revealed higher mean speaking fundamental frequency compared to previously published data obtained from elderly women. In the absence of normative data, the results of cepstrum analyses performed on vowels produced during connected speech revealed less periodicity for the 105-year-old woman's voice than for a 35-year-old woman's voice. The main finding of this study indicates that previously reported group trends regarding aging effects on mean speaking fundamental frequency of the female voice cannot simply be attributed to all elderly individuals. These results stress the importance, for clinical and research purposes, of recognizing the existence of considerable intra- as well as intersubject variability in the effects of aging on the voice.

Adult↗

PubMed1996

Vocal capacities in esophageal and tracheoesophageal speakers.

The present study investigated the vocal capacities of adult men who had undergone total laryngectomy. Esophageal (N = 10) and tracheoesophageal (N = 10) speakers were compared for the parameters maximum phonation time (MPT), maximum number of syllables that could be spoken on one air intake (SYLLS), dynamic range (DYN), frequency range (FREQ), and maximum intensity level (MIL). Statistical analyses yielded significant between-group differences for the parameters MPT, SYLLS, and MIL but not for DYN and FREQ. Thus, although the groups did not differ with respect to range of intensity and frequency measures, maximum performance on the durational and intensity measures was always less for the esophageal speakers than for the tracheoesophageal speakers. Pearson's product-moment correlations among these parameters were remarkably different for esophageal and tracheoesophageal subjects, suggesting that phonatory and aerodynamic factors interact differently in the two groups.

Aged↗