Noise induced hearing loss (NIHL) happens gradually – many people don’t realise they have it until it is too late

The harmful effects of hazardous noise are cumulative, which means the damage causing hearing loss increases over time through a series of repeated exposures.

The first indication that a worker may be exposed to hazardous noise levels is a temporary injury known as Temporary Threshold Shift (TTS).

TTS occurs when a person is exposed to hazardous noise that affects the functioning of the inner ear, which can cause temporary hearing loss. After a period of time away from noise, hearing may be restored.

With each further exposure a person has to hazardous or loud noise, the hair cells (cilia) in the cochlea (inner ear) gradually lose their ability to recover, become non-responsive to sound and will eventually die – causing permanent hearing loss.

The effects of NIHL can take some years to be noticed.

At first, most people aren’t aware of any change in their hearing but, over time, it becomes more noticeable, e.g. a worker may have difficulty hearing what family and co-workers say clearly or hearing sounds that are necessary for working safely, like verbal instructions – even warning signals.

The degree of hearing damage is dependent on:

• the level/s of noise a person is exposed to,
• how often and how long they have been exposed to the noise, e.g. workers who are exposed to hazardous noise on a daily basis at work are at a far greater risk of developing NIHL, and
• their susceptibility to noise