Speech Droplets Velocity – SpeeD Vel

The end of the containment allowed social and professional activities resumption while raising questions about the risk of SARS-CoV-2 spreading and protective measures to involve. Conversations (normal speech) or professional interactions (loud speech) have been identified as an increased risk of SARS-CoV-2 exposure related to high production of droplets in the expired air. Potential COVID-19 transmission by speech is an issue frequently raised in medias highlighting the imprecise and contradictory data emerging in literature.

Here, we propose a systematic study analyzing the velocity of droplets in the expired air during different speech conditions (normal speech, projected, interacting). This will allow to accurately define droplets dispersion and provide objective data regarding the potential risk of contamination to health authorities. Our aim is the SYSTEMATIC STUDY OF DROPLETS PRODUCED DURING SPEECH ACCORDING TO THE VOICE INTENSITY AND TO THE PHONETIC CONTENTS (VOWELS, CONSONANT, INTONATION). This proposal is part of the theme "PREVENTION AND CONTROL OF INFECTION" and more particularly in "STUDY OF HUMAN AND ENVIRONMENTAL FACTORS INFLUENCING TRANSMISSION". This study is designed to provide reference data on droplets dissemination during speech, taking into account sound characteristics and speech conditions. Indeed, these results will be a strong base of knowledge for the implementation of protective measures in various fields: adaptation of masks, validation of distance measures in education and more generally professional environments.

To achieve this goal, the interdisciplinary and complementary team (Laboratoire Parole et Langage LPL specialized in phonetic sciences and Institut Universitaire des Sciences et Techniques de l’Ingénieur IUSTI specialized in fluid mechanics) involved in this project will have to tackle with the following challenging questions:
1) What is the velocity of the expired air during speech? We propose a systematic analysis of this velocity with a hot-wire flowmeter during production of a linguistic corpus exploring all the items of articulation of speech (in French) by a large cohort of 50 speakers
2) What is the number of droplets in the expired air during speech? We propose to use a Particle Analyser to obtain a kind of size spectrography of emitted particles, knowing the fact that trajectories of droplets is a function of the size/weight
3) What is the spatial dissemination of droplets in the expired air during speech? We will use high speed cameras to analyze velocity and trajectory of the cloud of particles emitted during speech following a preliminary study performed during the confinement (1)
4) At the end of the experimentations, all data will be entered and will allow Computational Fluid Dynamic (CFD) studies analyzing the transport, dispersion and evaporation of droplets emitted according to different speech conditions.

Then, in 9 months, we will be able to share with government agencies responsible for health instructions, and more generally the scientific community, our data concerning the different speaking situations, especially for loud voicing (education, professional). This will help to improve the security of the population and fall under the prevention component of the RA-COVID call for tenders.

(1) Giovanni A, Radulesco T, Bouchet G, Mattei A, Revis J, Bogdanski E, Michel J. Transmission of droplet-conveyed infectious agents such as Sars Cov2 by speech and vocal exercises during speech therapy : preliminary experiment concerning airflow velocity. Europ Arch ORL 2020 20-01484R1 published on line July 2020