PSEM Arrival
To try and simplify the situation, in the 1980s Working Group 4 of IEC Technical Committee 1 started to write a new standard for a dosimeter, but decided that for many good reasons, a new name was called for and the long - but more correct name - of Personal Sound Exposure Meter (PSEM) was used. WG4 was mainly made up of design engineers from the International Sound Level meter companies together with scientists from various national acoustic laboratories and a few academics. The result of their efforts became IEC 61252 :1993, the current PSEM standard. This has tolerance limits based on a Class 2 - what was a Type 2 - sound level meter, but because it is intended to be worn on the body, it has relaxed directional characteristics.
The favoured metric for many scientists was simply the sound exposure in pressure-squared-time, for example Pa2h and this was used for the PSEM standard and at a stroke this removed all the various options for measurement. However for health and safety legislation in Europe for legal purposes the metric chosen was the daily personal noise exposure level, LEP,d, which corresponds to LEX,8h as defined in international standard ISO 1999: 1990 clause 3.6, and is expressed in decibels A-frequency-weighted . In simple terms this is the normalised sound exposure expressed in decibels.
Read more about this topic: Noise Dosimeter
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