Noise Exposure  
When estimating the risk of hearing loss or determining if a work regulation noise limit is exceeded, the noise exposure must be measured and calculated. Noise exposure is the average noise level over a whole work day. To calculate the noise exposure level over a work day, both the length of time of each noisy task and the sound level near the ears must be known. Then the partial noise exposure for each noisy task can be calculated as well as the noise exposure level for a whole workday. Values in dB(A) cannot be added directly together in that dB is in a logarithmic scale. If one has for example a machine producing noise at 80 dB and then starts a similar machine in the same area, the sound level increases by 3 dB to a total of 83 dB. A doubling of the transmitted sound is therefore an increment of 3 dB. An increase of 3 dB results in a doubling of the wear on a person's hearing. If a person is exposed to a single noise source over a workday, a noise exposure level of 80 dB(A) is attained after:
