Rifle impulse noise affects middle-ear compliance in soldiers wearing protective earplugs.
OBJECTIVE
We tested middle-ear functioning in humans following intense exposure to noise. Noise generated by small caliber firearms was thought to have no effect on the middle-ear.


METHODS
A cross-over design. We measured middle-ear impedance, acoustic reflex, distortion product otoacoustic emissions (DPOAEs), and transient evoked otoacoustic emissions (TEOAEs) before and after practice rounds performed twice per day.


METHODS
Fifty-nine soldiers equipped with earplugs undergoing regular training for a special mission. The mean noise exposure (LAeq8h) was estimated to be 106 ±1 dB SPL.


RESULTS
Impedancemetry revealed a significant increase in the compliance and gradient of the tympano-ossicular chain after impulse noise exposure in the right and left ears. Acoustic reflex reactivity did not show a significant change. DPOAEs and TEOAEs were slightly decreased at 2 kHz, and showed a marked asymmetry in disfavor of the left ear. In soldiers with initial high reactivity of acoustic reflex, increased compliance was associated with a significant decrease in left TEOAEs at 1.5 and 2 kHz.


CONCLUSIONS
Our results suggest that the use of small-caliber firearms, even while wearing earplugs, affects middle-ear function and may play a role in the early stage of auditory fatigue encompassing tinnitus.
a Institut de Recherche Biomédicale des Armées (IRBA) , Brétigny-sur-Orge , France .|b INSERM U836, GIN , Grenoble , France .|c Univ. Grenoble Alpes, GIN , Grenoble , France .
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Job
d Institut franco-allemand de Saint Louis (ISL) , Saint Louis , France .
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Hamery
d Institut franco-allemand de Saint Louis (ISL) , Saint Louis , France .
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De Mezzo
e Section Technique de l'Armée de Terre (STAT) , Versailles , France , and.
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JC
Fialaire
a Institut de Recherche Biomédicale des Armées (IRBA) , Brétigny-sur-Orge , France .
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Roux
f Centre Médical des Armées (CMA des Alpes) , Varces , France.
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Untereiner
f Centre Médical des Armées (CMA des Alpes) , Varces , France.
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Cardinale
f Centre Médical des Armées (CMA des Alpes) , Varces , France.
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Michel
f Centre Médical des Armées (CMA des Alpes) , Varces , France.
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Klein
e Section Technique de l'Armée de Terre (STAT) , Versailles , France , and.
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B
Belcourt
D000158:Acoustic Impedance Tests; D000328:Adult; D001300:Audiometry, Evoked Response; D018592:Cross-Over Studies; D004430:Ear Protective Devices; D004432:Ear, Middle / Q000503:physiopathology*; D005389:Firearms; D006801:Humans; D008889:Military Personnel; D009623:Noise, Occupational / Q000009:adverse effects*; D009784:Occupational Diseases / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D016273:Occupational Exposure / Q000032:analysis / Q000517:prevention & control*; D017084:Otoacoustic Emissions, Spontaneous; D014012:Tinnitus / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D055815:Young Adult
Noise; firearms; medical audiology; middle-ear; otoacoustic emissions; tympanometry