625 Active control of incoming noise using high-directional parametric loudspeaker

Abstract

Recent development of high-directional loudspeaker based on parametric array has allowed sound transmission within a narrow range of acoustic space like 'spotlight'. Parametric array utilizes the high directive characteristics of ultrasonic sound, where the embedded difference component of two ultrasonic carrier waves is expanded as audible sound. This peculiar characteristic can be implemented as one measure for improving active noise control scheme controlling acoustic field locally and efficiently. In the present study, a new approach for active control of sound field inside enclosure is investigated using high directional parametric loudspeaker as a control source. The sound field inside enclosure is formed by the incoming noise through an opening placed on one face of the enclosure. Two cases are tested experimentally: in the first case, both the control source and the error microphone are placed outside the enclosure, and in the second case, they are placed inside. It is known that in the latter case, the suggested ANC system using high-directional sound source can mitigate sound effectively in comparison to use of conventional omnidirectional loudspeaker.