The use of anechoic chambers is necessary when sound measurement in optimum conditions is needed in a laboratory, that is, with maximum acoustic insulation from the external environment and an excellent coefficient of soundproofing (close to free-field) Inside an anechoic chamber it is possible to measure absolute values which are difficult to measure in other conditions.
For example the slight acoustic energy emitted by the components of domestic appliances in order to guarantee standards of comfort must not exceed 25-30 dB(A).
The characteristics which define the minimum performance of an anechoic chamber are described in ISO 3740. The dimensions of an anechoic chamber can vary according to the volume of the source to be analysed. A fundamental part of the construction of anechoic chambers are the doors, the gates and the ventilation systems, which obviously must have suitable acoustic standards.
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