Noise Dosimeter - Use of Dosimeters

Use of Dosimeters

The original dosimeters were designed to be belt worn with a microphone connected to the body of the dosimeter and mounted on the shoulder as near to the ear as practicable. These devices were worn for the full work shift and at the end would give a readout initially in percentage dose, or in some other exposure metric. These were the most common way of making measurements to meet legislation in the USA, but in Europe the conventional sound level meter was favoured. There were many reasons for this, but in general in Europe the dosimeter was distrusted for several reasons, some being.

• The cable was considered dangerous as it could catch on rotating machinery
• The dosimeter could tell you the level had been exceeded, but it did not say when this happened
• Workers could falsify the data very easily
• The device was big enough to affect the work pattern

In the USA - where most of the early devices were manufactured, these reasons did not seem to matter so much.

To remove these European objections, dosimeters became smaller and started to include a data store where the Time History of the noise, usually in the form of Short Leq was stored. This data could be transferred to a personal computer and the exact pattern of the noise exposure minute by minute plotted. The usual method used was to store data in the form of Short Leq, a French concept that helped to bring computers into acoustics. As well, dosimeters started to incorporate a second C-frequency-weighted channel that allowed the true peak to be indicated. By the time the PSEM standard was published, many major sound level meter companies - in both Europe and the USA had a dosimeter in their range. A typical noise dosimeter is shown in figure 2