Speech air flow with and without face masks

Donald Derrick,Natalia Kabaliuk,Mark Jermy,Peiman Pishyar-Dehkordi,Luke Longworth

doi:10.1038/s41598-021-04745-z

Abstract

Face masks slow exhaled air flow and sequester exhaled particles. There are many types of face masks on the market today, each having widely varying fits, filtering, and air redirection characteristics. While particle filtration and flow resistance from masks has been well studied, their effects on speech air flow has not. We built a schlieren system and recorded speech air flow with 14 different face masks, comparing it to mask-less speech. All of the face masks reduced air flow from speech, but some allowed air flow features to reach further than 40 cm from a speaker’s lips and nose within a few seconds, and all the face masks allowed some air to escape above the nose. Evidence from available literature shows that distancing and ventilation in higher-risk indoor environment provide more benefit than wearing a face mask. Our own research shows all the masks we tested provide some additional benefit of restricting air flow from a speaker. However, well-fitted mask specifically designed for the purpose of preventing the spread of disease reduce air flow the most. Future research will study the effects of face masks on speech communication in order to facilitate cost/benefit analysis of mask usage in various environments.

Highlights

Face masks slow exhaled air flow and sequester exhaled particles
The earliest modern-era face masks were made of g auze1, and were used in conjunction with outdoor-air treatments for containment of the Spanish influenza pandemic of 19182. Kellogg3 studied the efficacy of the face mask material, revealing that the gauze mesh allowed bacteria through the mask
Since pollen exposure is positively correlated with SARS-CoV-2 infection r ates8, presumably wearing masks during pollen season reduces the risk of catching COVID-19 by reducing pollen exposure

Summary

Introduction

Face masks slow exhaled air flow and sequester exhaled particles. There are many types of face masks on the market today, each having widely varying fits, filtering, and air redirection characteristics. This proliferation of face masks is especially relevant dating from April 3, 2020, when the CDC changed initially skeptical guidelines to recommend masks, allowing a range of masks including [1] surgical masks, [2] masks that fit properly and are made of tightly-woven breathable fabric like cotton, with 2 or 3 layers or an inner filter p ocket4 This change in guidelines, combined with the rapid increase in COVID19 cases dating from mid-March, led to a worldwide commercial response resulting in a wide range of readily accessible pollen, cloth, surgical, and dust masks–so many that there have been considerable environmental roll-on effects as a result. A qualitative systematic review of recent studies has shown that cloth face masks have minimal impact on virus escape during normal breathing, and should only be used for a short period of time in indoor spaces with poor ventilation–where the risk of having no mask is greatest–when no other options such as improving ventilation e xist

Objectives

Results

Conclusion