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Occupational Noise Survey

656 views. 2012-7-16 16:15 |

A listening test you may find useful to indicate sound levels is:
1. When the sound level is above 82dBA, you will find yourself having to shout to be clearly understood by someone at 1m.
2. When the sound level is above 88dBA, you will find yourself having to shout to clearly understood by someone at 0.5m.
The initial survey will show whether the following actions are required:
1. Below 82dBA: no further action
2. 82 to 85dBA: inform the worker of the noise monitoring results, the minimal risk of hearing loss, and the roles of hearing protection and audiometric testing.
3. Above 85dBA: a more detailed noise survey and other requirements of the Noise regulation, including education on the effects of noise on hearing and training on the use of hearing protectors.
Trading-off Rule
The trading relationship between time and sound level is known as the "3dB doubling rule"; that is, for every 3dB increase, the energy content doubles. To keep the noise dose the same, the exposure time must be halved:
82dBA over 8 hours=85dBA over 4hours=88dBA over 2hours=91dBA over 1hour=94 dBA over 0.5 hours, etc. (and each pair of values is equivalent to half of one day's acceptable noise dose of 50%)
When to Do a formal survey
A formal survey will follow an initial survey when:
1. the initial survey indicates the noise exposure level, LEX, is likely to be greater than 85dBA, or noise exposure dose more than 100% per day.
2. An accurate value of workers' noise exposure is required by laws
3. More detailed information is required for noise exposure reduction methods.
4. More detailed information is required to select adequate hearing protection.
5. Genuine peak sound levels are above 140dBA.

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