Occupational Noise

Occupation health and safety is a big concern in Australia. Research indicates that there were around 16,500 successful compensation claims due to occupational noise between 2002 and 2007. The national standard for occupational noise is called, surprisingly, the "National Standard for Occupational Noise [NOHSC:1007(2000)]" and the "National Code of Practice for Noise Management and Protection of Hearing at Work [NOHSC:2009(2004)]" provides guidance on how the standard can be achieved. Both are available at Safe Work Australia.

The basic requirements of the standard are:

  • 85dB(A) Leq, 8 hour
  • 140dB (lin) peak

Leq is the equivalent continuous noise level that has the same energy as the measured level (it is an energy average). This noise level limit is set to protect the long term exposure to noise. Damage is caused when the hair cells within the ear do not receive enough blood flow due to the continuous vibrations cause by noise. They basically starve to death. This is also similar to black finger from virbation such as jack hammers.
Diver helmut for noise reduction!?!The 140dB(lin) peak is the upper limit at which no noise level can exceed. This is not because standard hearing protection does not provide enough noise reduction, but rather because at this noise level, the sound is so loud it is able to be transmitted to the cochlear directly through the bone of the skull. The only hearing protection that would be effective in this situation would be something similar to the deep sea divers helmut.

One of the requirements of the code is that workers who are regularly required to wear hearing protection are also required to have annual audiometric testing. In many cases now, organisations are finding it more cost effective to mitigate the noise source, rather than require hearing protection be worn and audiometric testing be conducted. Not only is the overhead of having audiometric testing reduced, the workplace is much safer where people do not need to wear hearing protection.
Matrix Acoustics is highly experienced in the application of the national code and is able to assist your organisation with noise surveys, hearing protection specification, noise mitigation design, and training.

The Sound Tool Box by Matrix Audio includes an occupational noise exposure calculator.