Audiometric (hearing) testing shows that we still have some way to go to defeat 'noise induced hearing loss' which progressively steals the ability to communicate and, if noise exposure continues unabated, eventually socially isolates its victims. New evidence shows that the use of personal MP3 players has opened another front for the development of this serious affliction in younger people.
Recent studies have added weight to the argument that incorrect use of headphones can lead to hearing loss at an early age. Hearing loss has long been known to affect workers in noisy tasks such as boilermakers, shooters, military personnel and others exposed to high noise levels for extended periods. What is now known as 'noise induced hearing loss' used to be called 'boilermaker's deafness' in a time when much of the first few years of a boilermaker's apprenticeship was spent repetitively hammering metal, often with no hearing protection.
A recent article in the Acoustics Bulletin1 highlighted that excessive noise exposure from listening to headphones or attending entertainment venues may be contributing to hearing loss. Unfortunately the effect of this hearing damage will not become apparent until many years later, leading the author of the article, Professor Richard V Harrison, to consider it a ticking time-bomb for over-exposed people in later life.
Professor Harrison is not alone in his opinion with Australian Hearing's principal audiologist, Janette Thorburn, expressing similar views in an article published in The Australian2. Janette states that modern headphones (known as earplugs or plugs) used in many MP3 players, iPods and phones deliver sound directly into the ear canal at levels up to 100dB(A). The fear is that prolonged exposure to sound levels in excess of 85dB(A) from such devices will lead to a higher incidence of hearing loss in the future.
Acoustic specialists tell us that no-one, not even old fogies, want to listen to music under 90 dB(A) in an entertainment venue, so this is probably the threshold for many people enjoying their favourite music. The regulation daily occupational limit for 91 dB(A) is two hours and at 100 dB(A), a level that a heavy metal enthusiast might prefer, this daily limit plummets to 15 minutes.
If you are listening simply for intelligibility in heavy traffic or windy conditions, it may be necessary to crank the volume over 85dB(A). These potentially damaging sound levels generated by MP3 players are matched by the potential for extended exposure durations. Exposures combine recreational use during almost every sporting and passive recreational activity with waterproof MP3 players now available for swimmers and in top end wetsuits to enhance the surfing experience.
Add to this the use of MP3s in the workplace to liven up uninteresting jobs and during long boring commutes and there is little doubt that the MP3 has the volume and duration hearing damage duet well covered!
All this complicates the issue of occupational noise-induced hearing loss, making it difficult to distinguish between work or recreation caused hearing loss and to strike a balance between the personal and productivity benefits of listening to something enjoyable while doing something less enjoyable (like repetitive work) and safety risks caused by the distraction of music, podcasts etc.
There are positive, preventative actions to deal with this issue. A better understanding of the work related risk is possible through periodic occupational noise assessments and audiometric tests. Systematic, accurate measurement of work related noise, exposure assessment and control to the occupational standard provides a compelling argument that the cause of any noise-induced hearing loss may lay outside the workplace.
Audiometric testing also provides a powerful "one on one" opportunity to demonstrate the specific, personal impact of noise exposure and to head off serious loss in its early stages. Educating staff to the real dangers of excessive noise both at work and at home can reduce the risk of hearing loss.
Many MP3 players have a facility for capping sound levels at 85dB(A) or some other low risk level and there is anecdotal evidence that workshops where MP3 sound levels are measured and the users educated in the dangers and appropriate listening levels are effective in changing behaviour.