Biomedical subjects

B Cranen

Publications and source records attributed to B Cranen.

4 recordsLinked to original sources

PubMed1988

On the measurement of glottal flow.

For developing a comprehensive description of voiced speech sounds in terms of a phonation and an articulation component, it is necessary to know to what extent the volume flow modulations at the entrance of the vocal tract are due to vocal fold motions and to what extent they are due to variations in the transglottal pressure. In order to be able to study this problem, it is important that the flow at the glottis can be measured during normal speech production in a reliable fashion. In this article, a flow measurement technique is described that differs from the more usual inverse filtering approach to the extent that the flow is not measured at the mouth, but much closer to the glottis. The technique is based on the measurement of pressure gradient. It is shown that the proposed method also leads to an inverse filtering problem, but that, since this problem is much simpler, the gradient method yields more reliable estimates of the shape of the glottal flow waveform, though without the zero flow level (dc component) and without a magnitude scale. By means of theoretical considerations about velocity profiles in pulsatile flow in cylindrical tubes, it is shown that the method for measuring flow during phonation proposed in this article may be expected to yield reasonable flow waveform estimates in a frequency region from any normal fundamental frequency to an upper frequency determined by the transducer sensitivity and separation and vocal tract geometry. In this case, the frequency limitation was estimated to be 1000 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Glottis↗

PubMed1987

On subglottal formant analysis.

When subglottal pressure signals which are recorded during normal speech production are spectrally analyzed, the frequency of the first spectral maximum appears to deviate appreciably from the first resonance frequency which has been reported in the literature and which stems from measurements of the acoustic impedance of the subglottal system. It is postulated that this is caused by the spectrum of the excitation function. This hypothesis is corroborated by a modeling study. Using an extended version of the well-known two-mass model of the vocal folds that can account for a glottal leak, it is shown that under realistic physiological assumptions glottal flow waveforms are generated whose spectral properties cause a downward shift of the location of the first spectral maximum in the subglottal pressure signals. The order of magnitude of this effect is investigated for different glottal settings and with a subglottal system that is modeled according to the impedance measurements reported in the literature. The outcomes of this modeling study show that the location of the first spectral maximum of the subglottal pressure may deviate appreciably from the natural frequency of the subglottal system. As a consequence, however, the comfortable assumption that in normal speech the glottal excitation function is constant and zero during the "closed glottis interval" has to be called into question.

Air Pressure↗

PubMed1985

Pressure measurements during speech production using semiconductor miniature pressure transducers: impact on models for speech production.

It appears that temperature instabilities are a major obstacle hindering the use of semiconductor strain gauge pressure transducers in speech research, especially when absolute pressure data are mandatory. In this paper a simple and reliable method for an in vivo calibration of this kind of transducer is described. The most important error source, the drift of the zero pressure level due to temperature changes, is discussed, and an estimation of the measurement accuracy which can be obtained is given. Moreover, some registrations of subglottal, supraglottal, and transglottal pressure are presented. It is shown that the pressure recordings allow us to obtain estimates of the volume flow in the trachea and pharynx. Analysis of those waveforms appears to lead to new insights into the physical processes underlying voice production. Specifically, an independent glottal contribution to the skewing of the glottal flow pulses is identified.

Calibration↗

PubMed1981

The phonochrome: a coherent spectro-temporal representation of sound.

Representation of simple stationary sounds can be given either in the temporal form by display of the waveform as function of time or in the spectral form by intensity and phase as function of frequency. For complex nonstationary sounds, e.g. animal vocalisations and human speech, a combined spectro-temporal representation is more directly associated with auditory perception. The well-known sonogram or dynamic power spectrum has a fixed spectro-temporal resolution and neglects phase relations of different spectral and temporal sound components. In this paper the complex spectro-temporal intensity density CoSTID) is presented as a coherent spectro-temporal image of a sound, based on the analytic signal representation. The CoSTID allows an arbitrary form of the spectro-temporal resolution and preserves phase relations of different sound components. Since the CoSTID is a complex function of two variables, it leads naturally to the use of colour images for the spectro-temporal representation of sound: the phonochrome. The phonochromes are shown for different technical and natural sounds. Applications of this technique for study of phonation and audition and for biomedical signal processing are indicated.

Acoustics↗