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Original Articles

Effectiveness of hearing protector devices in impulse noise verified with transiently evoked and distortion product otoacoustic emissions

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Pages 119-133 | Received 29 May 2007, Published online: 07 Jul 2009
 

Abstract

This study aimed to evaluate the effect of impulse noise on otoacoustic emissions (OAEs) while a passive non-linear earplug or an active level-dependent earmuff was worn.

Since none of the standardized attenuation measurement techniques, REAT (real ear at threshold), ATF (acoustic test fixture), or MIRE (microphone in real ear), is designed to test both types in real-wearing condition, OAEs, suitable for detecting subtle changes in the functional integrity of the cochlear outer hair cells, are used.

First, DPOAEs (distortion product) and TEOAEs (transiently evoked) of 24 subjects were compared before, immediately after gunfire practice, and after one hour of non-exposure. Secondly, both types of OAEs were evaluated in 31 subjects before and after exposure during a five-day military practice.

Significant differences existed between the ears in most cases; the emissions from the right ear had a tendency to be more robust. There were no significant changes in OAEs either before and after exposure, or in the second experiment over multiple days. These findings suggest that the HPDs are able to prevent cochlear damage.

Abbreviations
HATS=

head-and-torso stimulators

HPD=

hearing protector device

NIHL=

noise-induced hearing loss

REAT=

real ear at threshold

ATF=

acoustic test fixtures

MIRE=

microphone in real ear

EOAE=

evoked otoacoustic emission

TEOAE=

transiently evoked otoacoustic emission

DPOAE=

distortion product otoacoustic emission

OHC=

outer hair cell

Abbreviations
HATS=

head-and-torso stimulators

HPD=

hearing protector device

NIHL=

noise-induced hearing loss

REAT=

real ear at threshold

ATF=

acoustic test fixtures

MIRE=

microphone in real ear

EOAE=

evoked otoacoustic emission

TEOAE=

transiently evoked otoacoustic emission

DPOAE=

distortion product otoacoustic emission

OHC=

outer hair cell

Sumario

Este estudio pretende evaluar el efecto del ruido de impulso sobre las emisiones otoacústicas (OAEs) mientras se tenía colocado un tapón no lineal o un tapón orejera dependiente del nivel.

Puesto que las técnicas estandarizadas de medición de la atenuación, REAT (umbral del oído real), ATF (prueba acústica fija) o MIRE (micrófono en oído real) no están diseñadas para examinar ambos tipos en condiciones de oído real, utilizamos las OAE, que son apropiadas para detectar cambios sutiles de la integridad funcional de las células ciliadas de la cóclea.

Primero se compararon las DPOAE (productos de distorsión) y TEOAE (transitorios evocados) de 24 sujetos, antes, inmediatamente después de la práctica de tiro con arma y una hora después de la exposición. Después, se evaluaron ambos tipo de OAE en 31 sujetos antes y después de una práctica militar de cinco días de duración.

Existieron diferencias significativas entre los oídos en la mayoría de los casos; las emisiones del oído derecho tendieron a ser más robustas. No hubo cambios significativos en las OAE antes o después de la exposición, ni en el segundo experimento después de varios días.

Estos hallazgos sugieren que los dispositivos de protección auditiva (HPD) son capaces de prevenir el daño coclear.

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