An aeroacoustic microelectromechanical systems microphone phased array.

Abstract

Phased microphone arrays are useful tools for noise source localization using a process known as beam-forming. In scale-model wind tunnel experiments, the frequency range of interest can extend as high as 90 kHz. In both open and closed wall wind tunnels, microphones with high dynamic range are required to sense large turbulent pressure fluctuations from the open jet shear layer and the tunnel wall boundary layer. Microphones that meet the frequency and dynamic range demands of such experiments are readily available but expensive. When considering the high-sensor counts typically needed for phased array measurements, total sensor cost can be a limiting factor. The presentation will discuss a proof-of-concept phased array consisting of 25 piezoelectric microelectromechanical systems (MEMS) microphones arranged in a log-spiral pattern on a single printed circuit board. The microphones were designed in-house and have a dynamic range from 40–160-dB SPL and possess a resonant frequency greater than 100 kHz. A proven MEMS-based array that leverages the benefits of batch fabrication could cost significantly less than a traditional equivalent. The MEMS array will be characterized in the UF Aeroacoustic Flow Facility and compared to a conventional array of the same pattern comprised of 0.25-in. high-frequency microphones.