EN ISO 3745:2012 Acoustics
Determination of sound power levels and sound energy levels of noise sources using sound pressure. Precision methods for anechoic rooms and hemi-anechoic rooms

Testing to this standard builds upon the method outlined above for testing to ISO 3744, however, these tests can only be conducted in an anechoic or hemi-anechoic chamber. This method achieves the maximum possible accuracy level, Precision Grade (Grade 1).