Speech intelligibility during respirator wear: influences of respirator speech diaphragm size and background noise.

Abstract

This study assessed the effect of respirator speech device size on speech intelligibility and the impact of background noise on respirator communications effectiveness. Thirty-five subjects completed modified rhyme test (MRT) speech intelligibility testing procedures with and without a respirator under background noises of 40, 60, and 80 dBA. Respirator wear conditions included the use of one unmodified and three mechanical speech diaphragms modified to reduce the surface area of the vibrating inner membrane available for sound transmission. Average MRT scores decreased linearly as background noise levels increased for all conditions. Lower MRT scores were observed for all respirator speech diaphragm conditions compared to the nonrespirator condition within each noise category. Average MRT scores differed significantly between the unmodified speech diaphragm and one with a 70% reduced surface area with a 40-dBA background noise. However, MRT scores were similar between the modified and unmodified diaphragms at both the 60- and 80-dBA noise levels. These findings provide evidence that alternate designs of mechanical-type respirator speech devices can be achieved without further degradation of speech sound transmission.