NASA Glenn Research Center utilizes specialized instrumentation to measure airflow and sound for aviation noise reduction research. The facility employs tools such as particle image velocimetry, Raman spectroscopy, and various microphone configurations to collect data for validating noise prediction software.
Engineers at the center developed rotating microphone rake procedures in the 1990s to analyze modal content in turbofan engine tones. These systems have been deployed in diverse environments, ranging from low-speed wind tunnels to full-scale ground tests for turbofan engines.
The center operates the Array48 microphone system, which identifies noise sources in scale-model jet flows and full-scale military engines like the F404. Researchers also use embedded microphones in fan ducts to pinpoint noise generation on rotating blades.
To mitigate broadband noise and periodic disturbances, the team uses hotwire probes and Laser Doppler Velocimeters. These instruments record air velocity measurements between rotor and stator components, providing data to visualize disturbances and validate engine noise estimates.
