Improving the measurement and acoustic performance of transparent face masks and shields

Trevor J. Cox, George Dodgson, Lara Harris, Emanuele Perugia, Michael A. Stone, Michael Walsh

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)
27 Downloads (Pure)

Abstract

Opaque face masks harm communication by preventing speech-reading (lip-reading) and attenuating high-frequency sound. Although transparent masks and shields (visors) with clear plastic inserts allow speech-reading, they usually create more sound attenuation than opaque masks. Consequently, an iterative process was undertaken to create a better design, and the instructions to make it are published. The experiments showed that lowering the mass of the plastic inserts decreases the high-frequency sound attenuation. A shield with a clear thermoplastic polyurethane (TPU) panel had an insertion loss of (2.0 ± 1.1) dB for 1.25–8 kHz, which improves on previous designs that had attenuations of 11.9 dB and above. A cloth mask with a TPU insert was designed and had an insertion loss of (4.6 ± 2.3) dB for 2–8 kHz, which is better than the 9–22 dB reported previously in the literature. The speech intelligibility index was also evaluated. Investigations to improve measurement protocols that use either mannikins or human talkers were undertaken. Manufacturing variability and inconsistency of human speaking were greater sources of experimental error than fitting differences. It was shown that measurements from a mannikin could match those from humans if insertion losses from four human talkers were averaged.
Original languageEnglish
Pages (from-to)2931–2944
Number of pages14
JournalThe Journal of the Acoustical Society of America
Volume151
Issue number5
Early online date29 Apr 2022
DOIs
Publication statusPublished - 1 May 2022
Externally publishedYes

Bibliographical note

All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)

Funder

This work was funded by UK Research and Innovation under Grant No. EP/V051571/1.

Keywords

  • Speech communication
  • Acoustics
  • Microphones
  • Speech intelligibility
  • Speech perception
  • Signal processing
  • Signal-to-noise ratio
  • Natural materials
  • Polymers
  • Vibrometer

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