**5.2 Applicability of active noise control systems**

The main rules of thumb for applying an ANC system are the following:


is at least 2 500, that is, 1000 samples per second. Hence, the lower the frequency of the signal to be treated, the less demanding this aspect becomes. Please, note that the Nyquist theorem is a necessary condition but not a sufficient one to achieve a good description of the signal through sampling. At first, this was a major limitation for the use of the ANC systems. Advances in communications technologies have broken down this barrier.

