F.J. van Beinum

The influence of stoma occlusion on aspects of tracheoesophageal voice

In this study, speech of 21 laryngectomized patients is investigated under 2 different stoma occlusion conditions, i.e. direct digital occlusion of the stoma (by thumb or finger), and digital occlusion (by finger) via a special heat and moisture exchanger with speech valve (Provox Stomafilter). For both conditions, acoustical analyses of voice quality (various pitch, amplitude, tremor and harmonicity measures) were performed on a sustained /a/, the mean maximum phonation time was calculated, and a phonetogram was made. Acoustical analysis was possible in 13 of the 21 voices (for the other voices, the pitch was too low or the voice was too aperiodic), but no statistical significant differences were found for any of the acoustical parameters studied. However, the maximum phonation time was significantly longer, and the dynamic range significantly larger, under the Stomafilter occlusion condition. The maximum phonation time showed a relevant improvement in 57% of the patients, while the dynamic range showed a relevant improvement in 35% of the patients. In total, 75% of the patients experience an improvement in one or both of these speech characteristics when using the Stomafilter occlusion. It can be concluded that optimal stoma occlusion by means of a specialized device has a positive influence on two relevant parameters of prosthetic voice production: maximum phonation time and dynamic loudness range.

What's in a schwa? Durational and spectral analysis of natural continuous speech and diphones in Dutch

Although the schwa sound is by far the most frequent vowel in Dutch, it has up to now been phonetically the most neglected. We used an existing database of vowel sounds from focus words in spontaneous speech and in lexically the same text, read aloud by one male speaker, to analyse durational and spectral characteristics of schwas, and we compared the results with data on schwa diphones used in Dutch text-to-speech synthesis. It turned out that, contrary to what is usually thought, lexical schwa sounds in natural continuous speech are considerably shorter than other short vowels, that there is no strong consonantal influence on schwa duration, that schwa sounds display a spectral spread larger than any other vowel, and that surrounding consonants seem to play a role with respect to the midpoint formant distribution of the schwa within the whole vowel system. In no way can the schwa be considered as the ‘bench-mark’ of a speaker’s vowel system.