A personal noise dosimeter is the instrument of choice to measure the employee’s workplace noise exposure. Designs of noise dosimeters have evolved over the years from instruments that used to be worn on the belt with a cable microphone on the shoulder to now where the whole instrument is small enough to be worn on the shoulder during the shift. Earlier dosimeters provided a dose reading as a percentage of the allowable limit based on 100 percent representing the equivalent of 90 dB for a standard day.
While this single number approach is enough to satisfy the requirements of the regulations, a single overall number hides a multitude of information that can help to understand the noise exposure in more detail. The addition of time history samples collected at regular intervals during the day helps to show the noisier parts of the day and so provide the industrial hygienist with valuable information about when and where to concentrate active noise control or the provision of hearing protection to best effect. Most noise dosimeters now provide time history information, but on its own it may not always be that useful.