Broadband duct noise control by smart plate with piezoelectric elements

Low-frequency sound control has been receiving increasing attention in recent years since the existing noise reduction technology is mainly effective at middle-to-high frequency range. Some newly introduced passive resonance structures can work at low-to-middle frequency range but the bandwidth is very narrow. This study explores a semi-passive strategy, which is evolved from the low-frequency resonant structure but controlled by a shunt circuit and piezoelectric ceramics (PZT). The proposed smart sound reflector consists of a thin plate covering on a side-branch cavity and a shunted PZT patch on the plate. The smart wave reflector is installed on the lateral surface of the main duct. When the plate structure reflects incident waves at some specific frequencies in the flow duct, the piezoelectric material can act as a sensor and actuator simultaneously to control the sound reflection of the plate. The theoretical model built in this study has shown that the proposed smart plate with a side-branch backing cavity can effectively reflect sound waves in the low-to-middle frequency range.