Design and Fabrication of a Small Open Anechoic Wind Tunnel: Part 1

Abstract

Anechoic wind tunnels are essential for studying aerodynamic noise, but their small-scale design poses challenges in balancing acoustic performance, flow quality and cost. This study presents the development and validation of a compact open-jet anechoic wind tunnel (2.5 m × 2.5 m × 2.5 m) with multi-layered sound-absorbing walls. The chamber’s acoustic performance was evaluated through sound uniformity tests and aerodynamic noise measurements using a G.R.A.S. 40PH free-field microphone. Results confirmed effective suppression of reflections above 500 Hz, with sound pressure levels showing <5 dB variation across measurement points. The tunnel demonstrated strong mid-to-high frequency (1-10 kHz) absorption, critical for airfoil trailing-edge and turbulence noise studies. However, low-frequency (100-500 Hz) performance indicated minor non-uniformities, suggesting opportunities for improved damping.