Adaptive periodic noise cancellation for the control of acoustic howling

Presents a new method of containing the effects of acoustic echoes. The method is based on an adaptive periodic noise canceller (APNC), itself a variation on the well-known adaptive line enhancer. A simple but effective solution to the problem of containing howling in public address and handset free telephone systems has been proposed in the form of an APNC based on a FIR filter and driven by the LMS algorithm. By means of computer simulations of an acoustic feedback loop, the ability of the system to contain any sustained tendency towards instability has been demonstrated with no noticeable degradation in the quality of the speech signal