Progress in active sound control

Anti-sound techniques enable acoustic and vibrational fields to be mimicked and cancelled by secondary sources. That is, an unwanted sound can be suppressed if it can be completely reproduced in amplitude and phase over a required frequency range and over an area of required extent by secondary sources. Devices for exploiting this aspect of linear wave fields has been experimented with for over 50 years but it is only in the last decade that active noise control have emerged as a practical possibility as a result of the rapid development of electronic sensing processing techniques.