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.

许多科学报告表明，无症状和有症状的个体可能在社交互动中的对话中促进了COVID-19的传播。在讲话过程中会发生液滴的发射，但是很少有研究记录流量以提供传输机制。由于缺乏了解，因此无法就降低风险和减轻风险的策略（例如“ 6英尺法则”）获得知情的公共卫生指导。在这里，我们使用量级估计，数值模拟和实验室实验分析呼吸和说话过程中的流量，包括语音功能。我们记录了排出气流的时空结构。爆破音（如“ P”）的语音特性导致定向传输增强，包括夹带周围空气的喷射流。我们重点介绍呼出物质的运输距离的三种截然不同的时间尺度定律，其中包括：1）在短距离内（<0.5 m）在不到一秒的时间内进行运输，由于语音的复杂性，角度变化较大；2）更长的距离，〜1 m，其中定向传播是由对应于爆破音的单个涡旋推动的；3）大约2 m甚至更远的距离，其中句子中的连续爆破音有效地对应于一连串的抽吸，形成圆锥形的喷射流。后者规定了对话中的长时间传输。我们相信这项工作将为人们思考通气，气溶胶运输在人类和其他动物疾病传播中的作用，并更好地理解语言空气动力学，即航空声学。