Acoustic characteristics of fricatives, amplitude of formants and clarity of speech produced without and with a medical mask.
Duy Duong Nguyen, Antonia Chacon, Christopher Payten and 5 others
PMID 35166414WHAT IT FOUND
Speech produced with surgical or KN95 masks had significantly lower amplitude for fricatives like /s/ and /ʃ/ and was rated as less clear by experts.
Vowel formant amplitudes did not change. Clinicians should expect reduced fricative energy when wearing masks.
Key findings
01Spectral amplitude of fricatives /f/, /s/, /ʃ/, and /z/ was significantly lower when speakers wore surgical or KN95 masks compared to no mask.
02Expert raters perceived speech produced with masks as significantly less clear than speech produced without masks.
03Amplitude of the first three formants for vowels did not differ significantly between mask and non-mask conditions.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study did not strictly control for within-speaker variability in phonation, so some differences might reflect natural speech variation rather than mask effects. Only four specific fricatives (/f/, /s/, /ʃ/, /z/) and three vowels were analyzed; findings may not generalize to other sounds. Raters used online tools with self-adjusted volume, which could affect clarity judgments. The study design did not allow confirmation of whether mask materials or acoustic deflection caused the amplitude changes.
Declared interests
There were no conflicts of interest.
The easy way to misread this
Do not assume masks make speech unintelligible. The study found reduced clarity ratings and lower fricative amplitude, but did not measure actual word recognition or communication breakdown. Also, vowel formants were unaffected, so the issue is specific to high-frequency consonants, not general speech quality.