Active noise systems for reducing outdoor noise

An ANC system prototype designed for stationary noise control linked to traditional noise barriers was initially developed by authors in the past years. The encouraging results initially obtained have shown that ANC systems are feasible and should be further investigated to improve their performances. Nevertheless, FXLMS algorithm, considered in the first prototype architecture, is known to be affected by convergence problems that generally arise when a system fails to properly identify the noise to be cancelled; this process may (and often does) yield an instable system, where the control algorithm tries to catch-up its own sound, increasing the overall sound pressure level on the targets as in “avalanche” effect, potentially leading to damage fragile instrumentation. Hence, instability is unacceptable in practical applications and must be avoided or prevented. With this respect, in this manuscript some more robust alternative ANC algorithms have been investigated and experimentally verified.