Otoacoustic emissions in detection of pre-clinical noise induced cochlear damage in military personnel

Background: Objective of current study to analyse the utility of TEOAEs and DPOAEs to detect cochlear damage due to chronic exposure to firearm noise in Indian military personnel at a preclinical stage. Military personnel are exposed to firearm noise and need to be assessed for cochlear damage periodically. Methods: This cross sectional study was conducted from May 2004 to Apr 2005. Indian army soldiers and general civilian population were included in the study. The TEOAE and DPOAE parameters of two control groups (civilians, no noise exposure, no HL: control group 1; soldiers, noise exposed, hearing loss: Control group 2) were compared with the study group (soldiers, noise exposure, no hearing loss: Study group). Results: TEOAE amplitudes of the study group varied significantly from those of both the control groups at almost all frequencies. Overall amplitude too followed a similar trend. However, although the DPOAE amplitude of the study group was less than that of control group 1, the difference was not significant. The DPOAE amplitude of study group varied significantly from control group 2. Conclusions: TEOAEs proved to be useful to distinguish between green ears and ears chronically exposed to impulse noise with and without hearing loss. But DPOAEs proved to be useful in distinguishing only between normal hearing from hearing loss ears.