Instrumentation and techniques for acoustic research in wind tunnels

Several methods for aiding acoustic measurements inside wind tunnels are described; these include: placing acoustic material in the test section, using low tip-speed drive fans for reducing background noise, using proper microphone strut design for low wind noise, using directional receivers, and simulating the reverberant noise fields. The instrumentation and techniques were developed for acoustic research in both a small and a large closed-test-section wind tunnel at NASA Ames Research Center, and may be applicable to many different types of aeroacoustic wind tunnels.