Research on tunable bandgap characteristics of the phononic crystal duct with piezoelectric thin plates for the broad noise reduction

Abstract

To achieve adjustable mid-low frequency noise reduction characteristics in pipeline systems, one hybrid phononic crystal duct with piezoelectric thin plates is proposed. Firstly, phononic crystal duct model with Helmholtz mufflers and built-in piezoelectric thin plates is established to reduce low-to-mid frequency noise in the duct. The theoretical transmission loss is verified using simulation methods, revealing the sound attenuation law and bandgap mechanism. Under the shunting effect of the RLC circuit, three locally resonant bandgaps are generated: the mechanical locally resonant band gap introduced by the thin plate, acoustic locally resonant band gaps caused by the Helmholtz muffler cavity structure, and the electromechanical locally resonant band gaps dominated by the shunting circuit. By adjusting the shunting circuit, the acoustic impedance of the piezoelectric thin plate can be controlled, and then the acoustic characteristics of low and medium frequencies will change. For the shunting circuit composed of inductance, capacitance and resistance in series, the inductance and capacitance can adjust the position of the three band gaps; the negative capacitance can effectively enhance the tunability of the electromechanical locally resonant band gap, which is helpful to obtain the low-frequency band gap; while resistance primarily affects the magnitude of acoustic attenuation within the bandgap. Subsequently, based on the analysis of the noise characteristics of the air-assisted system of one fuel cell vehicle, one hybrid phononic crystal duct with compact structures is designed to achieve a broadband duct noise reduction of 330 Hz–4000 Hz.