Effects of Ear Protective Devices on the Intelligibility of Speech in Noise

Articulation tests were conducted to determine the intelligibility of speech in the presence of noise when listeners did not wear earplugs and when listeners wore earplugs (NDRC Ear Wardens). It was found that with a reverberating signal from a public-address system and in the presence of noise that raises the open-ear speech threshold by 60 db or more, the wearing of Ear Wardens increases the intelligibility of speech. But, with direct person-to-person speech, the ambient noise must be of sufficient intensity to raise the speech threshold by 80 db or more before Ear Wardens may be used without interfering with the reception of speech. Since in some military and industrial situations noise is generated that raises the threshold for hearing speech by more than 80 db, the use of suitable earplugs, under those conditions will: (a) maximize the reception of speech and (b) afford protection against the deafening, fatigue, and annoyance effects commonly attributed to sustained intense noise.