3. Psychoacoustic aspects of active control

The first indicator that has been used to measure the effectiveness of active control is the attenuation, in dB, of primary noise (cf. [ BR 3 010 , § 2]. Unfortunately, this reduction in the physical noise level does not translate into an equivalent reduction in the noise level perceived by a listener. From a subjective point of view, attenuations are often less than the physical measurements would suggest. Using dBA to try and assess the reduction in perceived level does little to improve matters:

• the shape of the frequency weighting curve that defines dBA...