TY - JOUR
T1 - Speech can produce jet-like transport relevant to asymptomatic spreading of virus
AU - Abkarian, Manouk
AU - Mendez, Simon
AU - Xue, Nan
AU - Yang, Fan
AU - Stone, Howard A.
N1 - Funding Information:
We thank the NSF for support via the RAPID Grant CBET 2029370 (program manager is Ron Joslin). M.A. thanks the IRN "Physics of Living Systems" (CNRS/INSERM) for travel support, as well as K. Meersohn for pointing out the importance of plosives in almost all languages of the world. S.M. thanks V. Moureau and G. Lartigue (CORIA [Complexe de Recherche Interprofessionnel en Aérothermochimie], UMR 6614) for providing YALES2, which served as a basis for the development of YALES2BIO. Simulations with YALES2BIO were performed using high-performance computing resources from GENCI-CINES (Grants A006 and A0080307194) and from the platform MESO@LR. S.M. acknowledges the LabEx Numev (Convention ANR-10-LABX-0020) for support for the development of YALES2BIO. We thank A. Smits for loaning the fog machine and P. Bourrianne and J. Nunes for help measuring flow rates during breathing.
Funding Information:
ACKNOWLEDGMENTS. We thank the NSF for support via the RAPID Grant CBET 2029370 (program manager is Ron Joslin). M.A. thanks the IRN “Physics of Living Systems” (CNRS/INSERM) for travel support, as well as K. Meersohn for pointing out the importance of plosives in almost all languages of the world. S.M. thanks V. Moureau and G. Lartigue (CORIA [Complexe de Recherche Interprofessionnel en Aérothermochimie], UMR 6614) for providing YALES2, which served as a basis for the development of YALES2BIO. Simulations with YALES2BIO were performed using high-performance computing resources from GENCI-CINES (Grants A006 and A0080307194) and from the platform MESO@LR. S.M. acknowledges the LabEx Numev (Convention ANR-10-LABX-0020) for support for the development of YALES2BIO. We thank A. Smits for loaning the fog machine and P. Bourrianne and J. Nunes for help measuring flow rates during breathing.
Publisher Copyright:
© 2020 National Academy of Sciences. All rights reserved.
PY - 2020/10/13
Y1 - 2020/10/13
N2 - Many scientific reports document that asymptomatic and presymptomatic individuals contribute to the spread of COVID-19, probably during conversations in social interactions. Droplet emission occurs during speech, yet few studies document the flow to provide the transport mechanism. This lack of understanding prevents informed public health guidance for risk reduction and mitigation strategies, e.g., the "6-foot rule." Here we analyze flows during breathing and speaking, including phonetic features, using orders-of-magnitude estimates, numerical simulations, and laboratory experiments. We document the spatiotemporal structure of the expelled airflow. Phonetic characteristics of plosive sounds like "P" lead to enhanced directed transport, including jet-like flows that entrain the surrounding air. We highlight three distinct temporal scaling laws for the transport distance of exhaled material including 1) transport over a short distance (<0.5 m) in a fraction of a second, with large angular variations due to the complexity of speech; 2) a longer distance, ~1 m, where directed transport is driven by individual vortical puffs corresponding to plosive sounds; and 3) a distance out to about 2 m, or even farther, where sequential plosives in a sentence, corresponding effectively to a train of puffs, create conical, jet-like flows. The latter dictates the long-time transport in a conversation. We believe that this work will inform thinking about the role of ventilation, aerosol transport in disease transmission for humans and other animals, and yield a better understanding of linguistic aerodynamics, i.e., aerophonetics.
AB - Many scientific reports document that asymptomatic and presymptomatic individuals contribute to the spread of COVID-19, probably during conversations in social interactions. Droplet emission occurs during speech, yet few studies document the flow to provide the transport mechanism. This lack of understanding prevents informed public health guidance for risk reduction and mitigation strategies, e.g., the "6-foot rule." Here we analyze flows during breathing and speaking, including phonetic features, using orders-of-magnitude estimates, numerical simulations, and laboratory experiments. We document the spatiotemporal structure of the expelled airflow. Phonetic characteristics of plosive sounds like "P" lead to enhanced directed transport, including jet-like flows that entrain the surrounding air. We highlight three distinct temporal scaling laws for the transport distance of exhaled material including 1) transport over a short distance (<0.5 m) in a fraction of a second, with large angular variations due to the complexity of speech; 2) a longer distance, ~1 m, where directed transport is driven by individual vortical puffs corresponding to plosive sounds; and 3) a distance out to about 2 m, or even farther, where sequential plosives in a sentence, corresponding effectively to a train of puffs, create conical, jet-like flows. The latter dictates the long-time transport in a conversation. We believe that this work will inform thinking about the role of ventilation, aerosol transport in disease transmission for humans and other animals, and yield a better understanding of linguistic aerodynamics, i.e., aerophonetics.
KW - Asymptomatic transmission
KW - COVID-19
KW - Pathogen dispersion
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U2 - 10.1073/pnas.2012156117
DO - 10.1073/pnas.2012156117
M3 - Article
C2 - 32978297
AN - SCOPUS:85092690923
SN - 0027-8424
VL - 117
SP - 25237
EP - 25245
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 41
ER -