This includes if they occur in work environments, whether for verification of noise community, if for General measurements, Yes to diagnose the condition of machines, whether to verify the effects of isolation, etc. In any of the variants the selected computer must comply with standards which establishes the International Electrotechnical Commission (IEC) for measuring instruments. In the case being analyzed must be accordance with IEC 651 (1979) and the IEC 804 (1985). Other both international and national standards (e.g. ANSI S1.43-1983) is possible, but it cannot ignore is that the effective implementation of regulations established by the IEC the instrument’s performance assurance results.

Each rule to adjust the sound level meter comes associate, invariablenente, with the type or class of sound level meter (see below the instrument class). TEN aspects to consider the following proposed ten indicators technicians who should facilitate the task of choosing a sound meter: the instrument class: can be of class 0, 1, 2, 3. depends on the precision sought in measurements and use requiring the instrument. Class 0: used in laboratories. It serves as a reference. Class 1: employment in precision field measurements.

Class 2: use in general field measurements. Class 3: used to perform recognition. Approximate measurements. Supplied microphone: this aspect is very important since it determines the range of frequencies that can analyze the instrument. Here microphone type, its sensitivity, frequency band, capacitance (pF) and the inherent noise level must be taken into account. The latter is not more than the combination of electrical and thermal noise which suffers the MIC at 20oC (expressed in dB). It varies from one type to another frequency weighting. It is necessary to know, moreover, by which microphones is possible to exchange the one supplied. And, also, the response of the instrument before the infra and ultrasound, in the event that may be of interest. Measurement parameters: this aspect determines the types of measurements that can be made with the instrument.