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Biomedical subjects

W Decoster

Publications and source records attributed to W Decoster.

7 recordsLinked to original sources
PubMed2000

Longitudinal voice changes: facts and interpretation.

To study intraindividual vocal changes over time, a longitudinal research design is preferred. However, this procedure reveals many restrictions concerning methodology and interpretation, especially in cases of (semi)retrospective studies. This is illustrated by an investigation of the voices of 20 male Dutch-speaking reporters of the Belgian Radio Broadcasting service. These men read the same text they did 30 years previously for a digital registration. After having copied the high-quality archival recordings digitally, the results of the acoustical analysis of both recordings (recent and archival) were compared. This was done to search for the contribution of aging. In this article we report on the results of the speaking fundamental frequency (SFF) and the standard deviation of the SFF (SFFsd) as a measure of intraindividual variability, and the voice onset time (VOT). Results indicate that, in connected speech, SFF decreased, SFFsd became more restricted, and the VOT increased strongly. The interpretation of the results compels us to conclude that it is extremely difficult to define the specific effect of aging alone, since it is only one element among many others, including methodological concerns.

Adult↗
PubMed1997

Changes in spectral measures and voice-onset time with age: a cross-sectional and a longitudinal study.

In this study, we searched for changes in spectral features (during the sustained vowels [a] and [i]) and the voice onset time (VOT, of [pa] and [ka]) of the ageing voice. A longitudinal study (on 20 participants) and a cross-sectional study (on 265 participants) were conducted. The spectral parameters under consideration were: the difference in amplitude between the first and the second harmonic, the energy difference between the frequency band below 1 kHz and 2-4 kHz, and the energy difference between < 1 kHz and 4-5 kHz. The VOT was also measured. Comparing five age bands of men and women, the cross-sectional study revealed a stronger H2 relative to H1 for women above 60 years pronouncing both vowels [a] and [i]. A relatively stronger spectral level was found between 4 and 5 kHz in elderly men and women (60+) for [i] compared to young men and women (20-29 years). Significant differences in the longitudinal study were not identical to those of the cross-sectional study. After a time interval of 30 years, 20 men produced a relatively weaker 2- to 4-kHz part of the spectrum and the VOT became much longer. It was impossible to attribute the changes purely to the process of ageing. Situations and emotions also play an important role and contribute to the different findings of the two groups of participants under consideration.

Adult↗
PubMed1997

The ageing voice: changes in fundamental frequency, waveform stability and spectrum.

In the present study we searched for age dependent acoustic changes in the voice of 205 men and women divided in four age groups from 60 to 99 years old. Sixty young men and women served as a comparison group. The findings cover three domains of acoustic features. Firstly, the voice pitch of males and females congruate one to another, while range and variability both increase. The values of jitter, shimmer and harmonics-to-noise ratio (measures of microstability of frequency, amplitude and waveform resp.) reflect a growing voice instability. From all spectral characteristics, only the difference between the first and the second harmonic differs significantly when comparing young to old women.

Acoustics↗
PubMed1997

Temporary voice changes after uncomplicated thyroidectomy.

Voice characteristics were studied before and after thyroidectomy in patients with intact vocal fold motility. The speaking voice was acoustically analysed in 47 patients and phonetograms were made in 17 patients. Eight parameters were measured and the pre- and postoperative values compared. The results show that the most affected parameter was the pitch of the speaking voice. The fourth postoperative day there was, on average, a lower SFo and a smaller Fo range during speaking. Postoperatively a progressive normalisation took place. After three months there were no more statistical differences and, looking at the individual measures, the SF0 of all patients fell within 2 semitones from their preoperative level. Vocal quality was also altered in the first postoperative examination, as shown by the higher jitter and smaller harmonics. These measures normalised after two weeks. In the same way, the evaluation of the limits of the voice by means of the phonetogram, showed that the maximal performances in the intensity and pitch domain were decreased in the earliest postoperative period. Information about temporary voice change is useful in patients undergoing thyroidectomy.

Female↗
PubMed1982

Chromatographic assay of neomycin B and C in neomycin sulfate powders.

A chromatographic assay of neomycin sulfate powders on strongly alkaline ion-exchange resin (hydroxide form) is described. D-(+)-alpha,alpha-Trehalose was used as an internal standard. The amount of neomycin B and C in commercial samples was determined with the proposed method, and the results are compared with those obtained by microbiological assay. In addition, minor neomycin components were estimated by TLC and GLC methods.

Bacteria↗
PubMed1981

Determination of the relative amounts of the B and C components of neomycin by ion-exclusion chromatography using refractometric detection.

Refractometric detection can be used as a convenient alternative to ninhydrin colorimetric or polarimetric detection in ion-exclusion chromatography of neomycinn. The determination of the relative amounts of neomyci B and C using different detection methods is examined. The use of a resin of smaller granulometry and a medium-pressure chromatographic apparatus reduces the analysis time to less than 25 min.

Chromatography, Gel↗