Active Noise Control Using High-Directional Parametric Loudspeaker : Numerical Study on Radiated and Interfered Field(Mechanical Systems)

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 without adversely influencing vicinal space. In the present study, a new approach for active control of sound in free space is developed using high directional parametric loudspeaker as a control source. A numerical model of parametric array source is studied, and the calculated sound fields are compared with the measured fields formed by a commercial parametric loudspeaker. Furthermore, an approach for the active control of sound in free space is investigated, and the results are evaluated mainly from the aspect of the interfered sound field. It is known that the suggested ANC system can mitigate sound locally but cause less influence on sound field in circumferential space.