Psychoacoustic aspects of active control
Active noise 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...