Acoustic analysis of the effect of personal protective equipment on speech understanding: lessons for clinical environments

Objective:The use of various types of filtering facepiece class 3 (FFP3) mask have become commonplacesince the Covid-19 outbreak. These have been evaluated in terms of efficacy regarding aerosol filtrationbut less emphasis has been placed on the acoustic effects of such masks and their consequences for clin-ical communication.

Design:A microphone 65cm from a sound-producing Head and Torso Simulator (wearing the masks)was used to measure attenuation via a tone sweep. Predicted impact on speech reception in noise wasassessed by weighting the attenuations of cochlear excitation patterns by the frequency importance func-tion of the Speech Intelligibility Index.

Study sample:We evaluated acoustic attenuation properties of seven FFP3 masks and a Type IIR surgicalmask (as a comparator).

Results:The Type IIR mask had the smallest impact on SNR (2.6 dB with visor). Most FFP3s with an add-ition of a visor (if not already face covering) impacted SNR by approximately 6 dB. The 3 M 6000 was sig-nificantly worse (15.8 dB).

Conclusions:Mouth-and-nose covering FFP3s masks had similar effects on SNR ( 6.2 dB with visor). TheTecmen TM-H2 had several advantages over other masks evaluated. It was reusable, allowed lipreadingclues and the attenuation was similar to other FFP3s.