The Immediate and Long-Term Impact of Military Aircraft Noise on Hearing: A Cross-Sectional Comparison of Fighter Pilots and Ground Staff.

We examined the immediate and long-term impacts of military aircraft noise exposure on noise-induced hearing loss (NIHL) in fighter pilots and ground staff. We recruited 40 pilots, 40 ground staff, and 136 age-matched controls; all participants underwent hearing tests, including conventional pure-tone audiometry (PTA) (0.25-8.0 kHz), extended high-frequency (EHF) audiometry (9.0-18.0 kHz), and distortion-product otoacoustic emission (DPOAE) as a recent reference. A subsequent hearing test immediately after flight-mission noise exposure was requested. The results revealed higher recent hearing thresholds in pilots and ground staff than in controls. Threshold shifts at many octave band frequencies were also significantly elevated in ground staff. The grouped frequency threshold was significantly elevated in the 4-8 kHz high-frequency range. After a single flight-mission noise exposure, both ground staff and pilots showed decreased signal-to-noise ratios for DPOAE (1-8 kHz), whereas only ground staff showed significantly elevated left-ear hearing thresholds at 3, 11.2, and 12.5 kHz by conventional and EHF PTA. Fighter pilots and ground staff serve in hazardous noise-exposed environments that cause hearing damage and subsequent NIHL, but ground staff may be more vulnerable. A comprehensive hearing conservation program should be implemented to protect high-risk service members, and especially ground staff, from high-intensity noise exposure.

Evaluating the Function of the Medial Olivocochlear Bundle in Patients With Bilateral Tinnitus.

Purpose No study has investigated the effects of contralateral noise (CN) on speech-in-noise perception (SINP) in listeners with tinnitus. The mechanisms underlying the involvement of medial olivocochlear (MOC) reflex with SINP remain to be elucidated. This study aimed to investigate the MOC function in patients with bilateral tinnitus by measuring distortion product otoacoustic emission and SINP. Method Eighteen patients with bilateral tinnitus (one male and 17 females; age: M ± SD = 45.61 ± 10.18 years) and 19 listeners without tinnitus (six males and 13 females; age: M ± SD = 34.11 ± 8.35 years) were recruited for the study. Each subject underwent distortion product otoacoustic emission measurement and the SINP test for both ears. The effects of CN on these two measurements were compared between tinnitus ears (TEs) and no-tinnitus ears (NTEs). Results The presence of CN significantly reduced distortion product (DP) amplitudes and improved SINP for TEs, and the amounts of DP suppression and SINP improvement were similar to those in NTEs. Improvement of SINP was positively correlated with DP suppression at 6185 Hz for NTEs and at 1640 Hz for TEs. Conclusions The results of this study suggest that the amounts of DP suppression and SINP improvement were similar between listeners with and without tinnitus. For both ear groups, the MOC reflex was involved with SINP at specific frequencies. Any clinical test outcomes with regard to the MOC bundle in patients with tinnitus should be interpreted with caution until further studies are conducted.