Noise Level Assessments : When can sound be harmful in the work place?
- by Christina Hryniuk
Noise is a common health hazard in the workplace. Exposure to loud noises can cause stress. It also makes it difficult for people to talk in a workplace. Prolonged exposure to excessive levels of noise can result in permanent hearing loss. That’s why it’s important to test the levels of noise.
What high noise levels do to you
When the eardrum vibrates, it moves three tiny bones in your middle ear. This movement transmits the vibration to fluid in your inner ear. The movement of this fluid is then picked up by tiny hair cells that transfer the movement to nerves. The nerves send signals to your brain where they are recognized as sound.
Exposure to high-decibel sound for a long time can eventually damage the tiny hair cells. As a result, fewer signals are sent to the brain and you don’t hear as well because the hair cells can’t be replaced or restored. The damage is permanent.
When can sound be harmful and for how long?
It depends on the intensity of the sound. Most sounds made by people and in nature are harmless even over a long period of time. Loud sound, however, can damage your hearing after long exposure.
If people are exposed repeatedly and for long periods, sound may start to be harmful at about 80 dBA. A 10-decibel increase to 90 dBA means the sound is 10 times more intense. As sound levels increase, exposure times for workers must be reduced.
In Manitoba, a three decibel per doubling rule is used. That exposure means for every three dBA increase in the noise exposure above 85 dBA, the worker’s exposure duration must be reduced by one-half without exceeding the exposure limit.
The Use of Noise Dosimeters
During the assessment a worker will wear a noise dosimeter for their shift, which will measure their noise exposure through the day and give them their average noise exposure. A worker’s average noise exposure is used to determine if they are exposed to noise over 80 dBA.
Employers must post written reports of these assessments in a visible location at the workplace, ideally on the safety and bulletin board. All workers then must be informed and trained on the noise level they will experience at work and the hazards that presents.
Another useful feature is that they will log the noise data so when downloaded to a computer, the time history of noise can be viewed. This gives the ability to analyze when and where high noise exposures occur.