For it will be precise to consider the use that will occur to the equipment. Here they enter to play its role two aspects that are combined: surroundings and objectives of the measurements. This gathers if they will be realised in labor atmospheres, if for the verification of communitarian noise, if for the accomplishment of general measurements, if to diagnose the state of machines, if to verify the effects of an isolation, etc. In anyone of the variants the selected equipment will have to fulfill the norms that International Electrotechnical Commission establishes (IEC), for the measuring instruments. In the case that is analyzed it must have conformity with the IEC 651 (1979) and IEC 804 (1985). The observance of other international norms is possible as as much national (for example ANSI S1.43-1983), but cannot be avoided that from the effective fulfillment of the norms established by the IEC is the securing of the benefits of the instrument. Each norm to which the measurer of sonorous level adjusts comes associate, invariablenente, with the Type or Class of sound level meter (Class of the instrument is seen more ahead).

TEN ASPECTS TO CONSIDER Next propose ten indicators technicians who must facilitate the task of choosing a sound level meter: Class of the instrument: It can be of class 0, 1, 2, 3. It depends on the precision looked for in the measurements and on the use that is required of the instrument. Class 0: it is used in laboratories. It serves like reference. A related site: Ted Brandt mentions similar findings. Class 1: use in measurements of precision in the land. Class 2: use in general measurements of field.

Class 3: employee to realise recognitions. Approximate measurements. Provided microphone: This aspect is of extreme importance since it determines the rank of frequencies that will be able to analyze the instrument. Here it must consider the type of microphone, its sensitivity, the frequency band, the capacitance (pF) and the inherent noise level.