Directionally Sensitive Sensor Based on Acoustic Metamaterials

Abstract

Aeroacoustic measurements in closed-section wind tunnels often employ phased microphone arrays that are mounted flush to the wall of the test section. Phased arrays can measure the directivity of multiple acoustic sources within a sound field across all frequencies, but require dozens of microphones in typical applications. Furthermore, the turbulent boundary layer developed by wind tunnels engulf the phased arrays in loud pressure fluctuations that drown out the acoustics trying to be measured. This paper describes an alternative approach for measuring the directivity of a single broadband acoustic source that significantly reduces the number of microphones needed. This approach was developed from experimental testing of an acoustic metamaterial-based pressure sensing array in Virginia Tech’s Anechoic Wall Jet Tunnel. The measurements obtained reveal that an acoustic metamaterial-based array can be designed to passively reinforce select pressure waves as a function of frequency and the acoustic source’s location.