THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

Example Problem 39.10 Dosimeters 187What is the SEL for an equivalent sound level pressure of 98 dB(A) lasting 8 s?SolutionFrom Equation (9.7)SEL = 98 + 10 log 8 = 107 dB(A)Equation (9.6) provides the means of computing SEL when the integrating soundlevel meter does not offer an automatic SEL mode.9.10 DosimetersIt is not generally a practical matter to trail continuously an industrial workerperforming his or her duties in order to gauge the amount of noise exposure,particularly if that individual moves from place to place and is exposed to varyingdegrees of noise levels in the course of the day. A more convenient method ofmeasuring the total exposure is to have this person wear either a personal soundexposure meter or a noise dose meter (also called a noise dosemeter or noisedosimeter). The personal sound exposure meter, which is schematically describedin Figure 9.10, consists of a small microphone attached to a small extension cordso that it may be mounted close to the ear, a tiny amplifier that incorporates anA-weighting network, and a circuit that squares and integrates the electrical signalwith respect to time. The unit normally includes a sound exposure indicator whichcan come separate from the wearable unit. This device should be able to respondto a wide range of frequencies and sound levels without the presence of a manualcontrol. A latching overload indicator is also incorporated to provide a warningthat excessive sound pressure levels are occurring within the frequency range of theinstrument. The unit must be small, battery-powered, tamperproof, and constructedto withstand harsh environment.Figure 9.10. Schematic of a personal noise-exposure meter.