ASA 127th Meeting M.I.T. 1994 June 6-10

5aPP24. The effect of double hearing protection on speech intelligibility in a simulated aircraft noise environment.

Russell D. Shilling

Naval Air Warfare Ctr., Training Systems Div., Code 11, Orlando, FL 32826-3224

Gerald B. Thomas

Naval Aerospace Med. Res. Lab., Pensacola, FL 32508-5800

The ability to receive radiocommunications in a noise field while wearing double hearing protection (i.e., circumaural muffs and ear plugs) was assessed under simulated aircraft noise conditions. A version of the modified rhyme test [i.e., the tri-word modified rhyme test (TMRT)] was administered to nine student aviators in three noise level conditions [90, 100, and 110 dB (SPL)] and three hearing protector device (HPD) conditions. The HPD conditions included the traditional single protection (i.e., flight helmet with no earplugs) and double protection (helmet with properly fitted earplugs) configurations. A third condition sought to mimic the anecdotally reported more typical condition of ``sloppy fit'' earplugs with flight helmet; a ``real life'' double protection configuration. A repeated measures ANOVA provided significant main effects for noise level (p<0.001) and for hearing protector (p<0.001). Post hoc tests revealed the expected inverse noise level-speech score relationship (p<0.05) and significantly (p<0.05) better speech scores as the degree of hearing protection declined. The trade-off between hearing protection and speech reception in noise is discussed.