Abstract
In the active noise control, a transfer characteristics of an acoustic feedback path has a considerable influence on the stability of the control system. When an acoustic system has a feedback path, the control system often causes unstable behavior called howling. An approach to prevent the howling named directional control sound source (DCSS) is investigated and compared with an ordinary approach (howling canceller) in this paper. This DCSS is composed of two sound sources and a finite impulse response (FIR) filter. Active noise control using the filtered-x LMS algorithm is carried out in an L-formed duct model. It is shown that the DCSS approaches prevented the howling effectively through the experiment.
