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Underwater hearing thresholds and hearing mechanisms

Underwater hearing thresholds and hearing mechanisms
Underwater hearing thresholds and hearing mechanisms

Divers are often exposed underwater to very intense noise, the levels of which can be as high as 200 dB SPL. Appropriate noise limits can only be recommended for underwater use if hearing thresholds and hearing mechanisms are known. A comprehensive review of the literature related to underwater hearing thresholds (with and without air naturally trapped in the ear canals) and hearing mechanisms reveal that these are not understood and have been poorly evaluated.

Trials were undertaken to develop a test facility suitable for underwater sound field audiometry. It was established that underwater ambient noise may mask hearing thresholds and steps were taken to reduce this by isolating a water tank from ground vibration and reducing airborne sound. (A transfer appraoch function was required to record sound pressure levels below the electric noise of the underwater measurement system.) An audiometric methodology was developed which overcame the significant practical difficulties of testing hearing underwater and produced repeatable results.

A new underwater hearing threshold curve was established using 48 normally hearing sports divers. The results show that underwater hearing thresholds are on average 20-25 dB more sensitive than previously reported, and below 1 kHz this increases to 35 dB. Underwater hearing mechanisms were assessed using 24 normally hearing sports divers by effectively attenuating sound through the auricular pathway and by examining 2 subjects with conductive losses. This established the bone conduction pathway to be the primary route for hearing underwater.

The results mean that the A-weighted decibel scale, used to describe noise exposure limits in air, is not suitable for underwater use. A "W-weighting" scale equivalent to the A-weighting scale has been developed, and noise exposure limits have been proposed.

University of Southampton
Al-Masri, Mohammad Ahmad Oqlah
Al-Masri, Mohammad Ahmad Oqlah

Al-Masri, Mohammad Ahmad Oqlah (1993) Underwater hearing thresholds and hearing mechanisms. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Divers are often exposed underwater to very intense noise, the levels of which can be as high as 200 dB SPL. Appropriate noise limits can only be recommended for underwater use if hearing thresholds and hearing mechanisms are known. A comprehensive review of the literature related to underwater hearing thresholds (with and without air naturally trapped in the ear canals) and hearing mechanisms reveal that these are not understood and have been poorly evaluated.

Trials were undertaken to develop a test facility suitable for underwater sound field audiometry. It was established that underwater ambient noise may mask hearing thresholds and steps were taken to reduce this by isolating a water tank from ground vibration and reducing airborne sound. (A transfer appraoch function was required to record sound pressure levels below the electric noise of the underwater measurement system.) An audiometric methodology was developed which overcame the significant practical difficulties of testing hearing underwater and produced repeatable results.

A new underwater hearing threshold curve was established using 48 normally hearing sports divers. The results show that underwater hearing thresholds are on average 20-25 dB more sensitive than previously reported, and below 1 kHz this increases to 35 dB. Underwater hearing mechanisms were assessed using 24 normally hearing sports divers by effectively attenuating sound through the auricular pathway and by examining 2 subjects with conductive losses. This established the bone conduction pathway to be the primary route for hearing underwater.

The results mean that the A-weighted decibel scale, used to describe noise exposure limits in air, is not suitable for underwater use. A "W-weighting" scale equivalent to the A-weighting scale has been developed, and noise exposure limits have been proposed.

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More information

Published date: 1993

Identifiers

Local EPrints ID: 462416
URI: http://eprints.soton.ac.uk/id/eprint/462416
PURE UUID: 127cc38f-c152-4d70-8222-5a1de18d9e48

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Date deposited: 04 Jul 2022 19:07
Last modified: 04 Jul 2022 19:07

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Contributors

Author: Mohammad Ahmad Oqlah Al-Masri

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