Noise regulations (such as OSHA, MSHA, ACGIH and others) define action levels based on the Time Weighted Average, or % Dose. These are calculated from a worker's daily exposure to noise - they are not based on simple snap-shots of the noise level. The worker's noise exposure can be measured using a Noise Dosimeter such as the dBadge, which is worn throughout the working day. Otherwise, you can use a sound level meter to measure the average sound level at each location that the person is working at during a typical day.
To use the TWA and Dose Calculator, make noise measurements at each location and make note of how long the person works there. Enter these levels into the calculator.
In the example above, the person works for four hours at Machine 1, two hours at Machine 2 and two hours at Machine 3, making a total of 8 hours. Based on the USA OSHA regulations, the worker's Noise Dose is 209% and TWA is 95.3 dB.
The color coding on the screen is:
|Black||Level is below the action level.|
|Red||Level is above the action level but below the criterion level.|
|Red Bold||Level is above the criterion level.|
It is clear above that reducing the noise at Machine 2 will have the greatest influence on the daily noise dose.
The calculator will accept sound levels between 40 and 140 dB. Exposure times can be up to 24 hours at each location with a limit of 24 hours on the total exposure time.