Hearing loss in the Marine Corps

Audiograms of 11,577 made Marine officers and enlisted personnel are analyzed by age group and level of hearing for six frequencies: 500, 1,000, 2,000, 3,000, 4,000, and 6,000 Hz. Speech reception thresholds are determined for the average of 500, 1,000, and 2,000 Hz as recommended by the American Academy of Ophthalmology; high-frequency thresholds are determined for the average of 3,000, 4,000, and 6,000 Hz. Hearing impairment (greater than 25 dB ISO) for the speech frequencies is between 0.6% and 5.9%; for the high frequencies the range is 3.4% to 76.5%. For the high frequencies the largest increase in impairment is in the age group 35 to 44 years. No difference in the percentage distribution of hearing impairment is found between a statistically comparable group of civilians and Marines. This is in sharp disagreement with the hypothesis that a greater degree of hearing loss would exist in a military population exposed to more noise than a civilian population. Hearing impairment in the high frequencies caused by noise exposure is a problem of significant magnitude, especially above the age of 35, and may have an effect on speech intelligibility. However, the magnitude of the problem seems to be the same in the military and civilian populations studied.