Acoustic Effects of Wearing an M40 Mask with Hood on Speech Perception Anf Roduction

The objective of this experiment was to quantify and localize the effects of wearing the nuclear, biological, and chemical (NBC) M40 protective mask and hood on speech production and perception. A designated speaker's vocalizations of 192 monosyllables while wearing an M40 mask with hood were digitized and used as speech stimuli. Another set of speech stimuli was produced by recording the same individual's vocalizing the same monosyllables without the mask and hood. Participants listened to one set of stimuli during two sessions, one session while wearing an M40 mask with hood and another session without the mask and hood. The results showed that wearing the mask with hood gave most detrimental effects on the sustention dimension acoustically for both speech perception and production. The results also showed that wearing it was detrimental on vocalizing and listening to fricatives and unvoiced-stops. These results may be due to the muffling effect of the voicemitter in speech production and the filtering effects of the voicemitter and the hood material on high frequency components during both speech production and perception. This information will be useful for designing better masks and hoods. This methodology also can be used to evaluate other speech communication systems.