Wind Tunnel Testing of Directionally Sensitive Meander Metasurface and Sub-Resonant Sensor Arrays

Locating a sound source through the disruptive turbulent boundary layer’s pressure fluctuations is of great difficulty in aero/hydroacoustic applications. Conventional phased microphone arrays have trouble with this task because their diaphragms are exposed to the excess noise presented by these pressure fluctuations. In this paper, a meander-style metasurface was modified to make it flow-compatible. A sub-resonant sensor array was also designed to filter out convective pressure fluctuations and improve signal to noise ratio. These novel array designs were tested alongside a conventional phased array in Virginia Tech’s Stability Wind Tunnel. The metasurface array proved its ability to detect sound sources through a turbulent boundary layer although it was less accurate than the other two arrays. The sub-resonant sensor array displayed similar accuracy to the conventional phased array and provided insight into the design of through-cavities for convective pressure filtering. In combination, these results show promise for the development of novel acoustic array designs which can perform optimally through a turbulent boundary layer.