There are many different types of noise associated with the workplace. In general terms, they can result in two forms of hearing loss:
- noise induced hearing loss; and
- acoustic trauma.
Noise induced or sensori-neural hearing loss
This form of hearing loss is produced gradually from long term exposure to noise. Over its years of development, the condition begins by affecting high frequencies (usually at the 4000 Hz level) and eventually those at the lower levels.
Employees suffering from industrial deafness will have reasonably normal low frequency hearing, but distorted high frequency hearing. The volume of speech is unaffected, yet the clarity of speech, determined by consonants, lessens.
The percentage of binaural hearing loss tends to be linearly proportional to the duration of exposure to workplace noise.
When there is a single incident involved and it results in trauma to the acoustic organ, it is known as acoustic trauma.
Example
A RAAF member accidentally discharges his firearm in a vehicle, prior to dispersing birds from the runway. The member may suffer the effects of acoustic trauma.
An audiogram of a person suffering from acoustic trauma may show a flat loss, a high frequency loss or a low frequency loss.