3M eg3, eg4 user manual Illustration of how the dosimeter operates and processes

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Dosimetry

Noise dosimeter

What is a noise dosimeter and how does it compute measurements?

Essentially, a noise dosimeter is composed of the following: a microphone with a preamplifier, a weighted network, fast or slow response time, an internal clock, calculator, and memory to store logged data.

The illustration below is a diagram of a basic noise dosimeter. The microphone will, when exposed to a sound pressure, generate an electrical signal. The signal will be increased by a preamplifier, and then is regulated to an applicable level by the range control (dB range). The signal then goes through a filter set or weighting system. The next circuit is the response circuit, which controls the dampening of the readout. The response choices are typically Slow or Fast. Finally, the results will display on the dosimeter screen.

For computation and storage, the clock tracks the sampling time. Dosimeters record how long sound levels exceeded a set upper limit. The calculator computes an L-avg, a dose, a TWA, and other data. The memory stores all times, calculations, and measurements.

For post-processing, QSP-II is used to view and analyze your measurement results with the option to view and/or print reports.

		C
		A
Mic &	Range control	Apply filters	Fast/Slow	Measurement
Preamp	(70-140dB)	(A or C weighting)	Response	results on the Edge

Clock	Calculator	File storage
		system

QSPII – Manage setup and create graphs, charts and reports

Figure 1-2: Illustration of how the dosimeter operates and processes

053-644, Rev E Page 2 eg4 & eg3