A Study of Acoustic Reflections in Full-Scale Rotor Low Frequency Noise Measurements Acquired in Wind TunnelsDifficulties in obtaining full-scale rotor low frequency noise measurements in wind tunnels are addressed via residual sound reflections due to non-ideal anechoic wall treatments. Examples illustrated with the Boeing-SMART rotor test in the National Full-Scale Aerodynamics Complex (NFAC) 40- by 80-Foot Wind Tunnel facility demonstrated that these reflections introduced distortions in the measured acoustic time histories that are not representative of free-field rotor noise radiation. A simplified reflection analysis, based on the method of images, is used to examine the sound measurement quality in such "less-than-anechoic" environment. Predictions of reflection-adjusted acoustic time histories are qualitatively shown to account for some of the spurious fluctuations observed in wind tunnel noise measurements
Document ID
20100026469
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Barbely, Natasha L. (Georgia Inst. of Tech. Atlanta, GA, United States)
Sim, Ben W. (NASA Ames Research Center Moffett Field, CA, United States)
Kitaplioglu, Cahit (NASA Ames Research Center Moffett Field, CA, United States)
Goulding, Pat, II (Jacobs Technology, Inc. Moffett Field, CA, United States)
Date Acquired
August 24, 2013
Publication Date
January 20, 2010
Subject Category
Acoustics
Report/Patent Number
ARC-E-DAA-TN1156
Meeting Information
Meeting: American Helicopter Society Specialists'' Conference on Aeromechanics