Metasurface Lossless-Regulation Mechanism of Dynamic Acoustic Mass for Low-Frequency Aerodynamic Noise Control

To solve the problem of low-frequency aerodynamic noise control of Helmholtz resonators (HR) due to the frequency shift and amplitude reduction in acoustic attenuation caused by increasing fluid flow, the lossless regulation mechanism of the dynamic acoustic mass of a novel embedded-neck Helmholtz resonator (ENHR) metasurface is revealed through finite element simulation and wind tunnel experiments. Firstly, the flow-acoustic coupling aerodynamic simulation model based on the ducted silencer system is established. Then, the physical mechanism of lossless regulation of the dynamic acoustic mass for low-frequency aerodynamic noise reduction under incident fluid flow is studied specifically. Finally, a sub-wavelength and larger broadband ENHR metasurface comprising ten parallel cells is designed, in which an average transmission loss (TL) of 18.7 dB within 70-200 Hz with a Mach number (Ma) of 0.05 is achieved. The lossless regulation mechanism of dynamic acoustic mass with metasurface design would have an extensive potential application value in controlling low-frequency aerodynamic noise.