Dangerous Listening: The Exposure of Indigenous People to Excessive Noise

Health professionals working with Indigenous people are generally well aware of the widespread conductive hearing loss that occurs, especially among children, because of middle ear disease. Regular exposure to loud noise can also cause hearing loss. Noise-induced hearing loss is commonly found among people who work in noisy industries and environments. About 20% of non-Indigenous Australians are hard-of-hearing. Most of these are over 50 and were exposed to loud noise through work1. Noise-induced hearing loss is occurring increasingly among children. Research shows there have been significant increases in the number of children in the USA who show signs of noise-induced hearing loss most likely caused by the exposure to loud noise which is now a normal part of their modern lifestyles 2,3. Regularly listening to music on iPods and other MP3 players on high volume for a long time can damage hearing.

This article reports the preliminary results of a project i that seeks to better understand the noise exposure risks in many Indigenous lifestyles. Information on exposure to loud noise was gathered in two ways. Firstly, noise exposure surveys were carried out with Indigenous people, mostly in the Northern Territory but with some respondents from other states included. Secondly, people’s actual exposure to loud noise was measured using noise dosimeters in a variety of homes.

An occupational sound exposure level of no more than 85 decibels(dB) averaged over an 8 hour working day (LAeq 8h < 85 dB) or equivalent is the international criteria adopted by many countries including Australia and New Zealand. This is termed 100% doseii and can be described as the level of acoustic energy received by the person which should not be exceeded. This has been called the ‘allowable daily exposure’ (ADE). There is considered to be a significant risk of noise-induced hearing loss in the majority of persons exposed to levels which exceed this criterion on a long term basisA. The table below, used in occupational noise assessment, clearly defines the time average levels and corresponding time exposures, all of which are of equivalent acoustic energy (i.e. 100% dose) iii. If the time average sound pressure levels are in excess of 85 db over an 8 hour day then the time exposed must be correspondingly reduced so that exposure does not exceed the 100% dose. For each additional 3 dB the allowable time exposure to the noise level is halved. These are considered safe noise exposure times for different noise levels for adults in occupational settings over an 8 hour periodiv. It is unclear what the ‘safe’ level of noise exposure is for children but is widely thought that children’s hearing is more vulnerable to damage from excessive noise. The World Health Organization outlines studies of laboratory animals which support this.

Damage to hearing through noise exposure generally happens over time. The “accumulated effect of hours, days and years of exposure all contribute to an individual’s hearing damage and subsequent hearing loss”. This means exposure to loud noise regularly, early in life is of special concern. Some excessively noisy toys have created concern such as toy guns, juke boxes, whistles, clackers and rattles. Likewise the extensive use of personal listening devices such as iPods and MP3 players has raised cause for serious concern. It is not only the volume that is used but the length of time users can now listen. The earlier generation of personal listening devices such as the walkman or disc man could not be so easily used continuously for many hours as can the modern devices because they had less battery and storage capacity.