The only way to obtain the sound reduction index of a material is from standardised tests. The tests to obtain the acoustic reduction index of any material are carried out in accordance with the specifications established in the international standard UNE-EN ISO 10140-2. This standard establishes the test methodology to obtain the acoustic reduction index of a material, indicating the degree to which it can reduce the noise coming from outside the enclosure where it is to be installed.
The sound reduction index tests of this standard are carried out in standardised transmission chambers. These chambers are composed of two adjacent enclosures separated only by a partition surface where the sample to be tested is placed. For the test, noise is emitted in an omnidirectional loudspeaker in one of the enclosures (transmitting enclosure) and measurements are made of the noise reaching the other enclosure (receiving enclosure). From the difference between the noise emitted and the noise received at the receiver, the noise level that the material under test is capable of reducing is obtained.