JCJC - Jeunes chercheuses & jeunes chercheurs

Physical modelling of turbulent flow in the human upper airways – turbospeech

Submission summary

Scientific background and objectives Description of project, methodology Expected results Physical modelling of turbulent flow in the human upper airways 1. Scientific background and objectives Speech sounds are produced by fluctuations of the respiratory airflow through the upper airways. While important achievements are established with respect to the description of the glottal airflow, phenomena related to turbulent flow are not considered. Therefore, a major part of phenomena in the upper airways is left untreated: fricatives of course, but also the release of stop consonants, whispering, singing, aspiration noises, etc. Currently most flow models apply a set of `ad-hoc' empirical parameters to `adjust' for severe simplifications in the flow description which is assumed to be laminar, one-dimensional and stationary. Turbulent flow however is known to be characterised by a three dimensional development of an apparently random fluctuation of fluid movement superimposed to the mean flow. Moreover the transition from laminar to turbulent is not established immediately, but is in essence an instationary flow behaviour. Therefore, it is not so surprising that current approaches, although very valuable for some issues of glottal airflow description, needs further fundamental improvements to describe phenomena in the upper airways involving turbulent flow. The proposed research aims to contribute the the physical modelling, prediction and validation of turbulent flow in the upper airways. It is aimed to improve the understanding of phenomena relevant firstly to speech production and secondly to upper airways pathologies occurring in the larynx, vocal tract or nasal cavity. Considering the complexity of the problem and the achievements with respect to glottal flow modelling it is strived to look firstly at : - presence of turbulent flow in the glottal flow (glottal leakage, whispering) - interaction between glottal flow and ventricular folds (whispering, singing) - turbulent flow in the nasal cavity (speech, obstructive sleep apnoea) The sound produced by the interaction of the turbulent flow and the upper airways (vocal tract,...) is a long-term objective largely depending on the results of the proposed fundamental research. 2. Description of project, methodology A three step methodology will be followed in order to validate theoretical predictions inspired by a thorough analysis of the considered phenomena. - characterisation of the order of magnitudes of the relevant physical quantities on physiological `in-vivo' data (use of the EVA measuring station). - physical modelling and numerical simulation: in particular the application of turbulent boundary layer theory will be considered. Direct numerical simulations will be considered for a limited number of configurations. - `in-vitro' measurements on a mechanical model in a suitable experimental set-up allowing 1) to control the experimental conditions, 2) to perform repeatable measurements of the quantities of interest, 3) to visualise the flow in order to validate the physical modelling for different geometrical and flow conditions. The setup will be a further development of the current `ICP' setup allowing to measure velocity profiles, pressure distribution relevant to characterise the spatial and instationary flow behaviour necessary to perform the comparison with the theoretical predictions. 3. Expected results It is aimed to contribute to the field of theoretical and physical modelling of turbulent airflow in speech, but more in general in the upper airways. The fundamental results are expected to be applied not only to the field of speech production, but also to the challenging field of upper airway pathologies (sleep apnoea, vocal fold pathologies, etc.)

Project coordination

Annemie VAN HIRTUM (Autre établissement d’enseignement supérieur)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Help of the ANR 125,009 euros
Beginning and duration of the scientific project: - 36 Months

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