ACTIVE ADAPTIVE FEEDBACK-CONTROL OF SOUND FIELD

A new active adaptive feedback control algorithm (F. B. LMS) was devel oped in this paper mainly for the purpose of reducing aerodynamically self-oscillating noises. This is an algorithm which reconstructs the F iltered-X-LMS to a feedback type and which needs only error signals. A simple experiment using a straight duct proved that this method could increase acoustic damping in a closed sound field by controlling the secondary source just like a sound-absorbing wall. This method was als o proven to be effective for reducing periodic noises which had period ic causality. This method was applied to reduce a cavity tone and a re sonant noise of a model tube bundle which were typical self-oscillatin g noises, and satisfactory results were obtained. It was also successf ully applied to reduce periodic noises such as those in a cab of a con struction machine radiating from engine, cooling fan and oil hydraulic pump.