Acoustic instruments to measure sound (sound level meters - see Fig. 1) and related equipment such as sound calibrators (see Fig. 2), as well as instruments to measure human hearing functions, (audiometers - see Fig. 3), are not usually subject to legal control. In Europe, only a few countries (for example Austria, Czech Republic, France, Germany, Poland and Switzerland) prescribe type approval based on pattern evaluation and/or regular verification of individual instruments. The situation is similar outside Europe, which is surprising considering that millions of people suffer from excessive noise, especially in industrialized countries.
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