Improvement in the Source Localization Accuracy using a Microphone Array Adjacent to the Main Flow of Wind Tunnel

• Published in: Journal of Environment and Engineering Vol. 5; no. 2; pp. 287 - 297
• Main Authors: YAMAZAKI, Nobuhiro, NAGAKURA, Kiyoshi, UDA, Toki
• Format: Journal Article
• Language: English
• Published: The Japan Society of Mechanical Engineers 2010
• Subjects: Acoustic noise; Acoustics; Aeroacoustic Noise; Arrays; Free Shear Layer; Localization; Mathematical models; Microphone Array; Microphones; Position (location); Shear layers; Wind Tunnel
• ISSN: 1880-988X; 1880-988X
• DOI: 10.1299/jee.5.287

In this study, we propose a method to improve source localization accuracy in a wind tunnel test by using a microphone array. On the basis of a model of the acoustic path passing through a free shear layer, we installed the microphone array adjacent to the main flow to avoid refraction and dissipation in the free shear layer. Flow-induced noise due to the interference with the main flow is reduced effectively by calculating the cross spectrum between the respective outputs of two pairs of 2-D microphone arrays. The effects of these techniques are verified by the acoustic performance test using a standard source device with wind exposure. It was found that this calculation method is effective even at a uniform wind velocity of 300 km/h and enables acoustic measurements adjacent to the main flow. Accurate noise source localization can be achieved by installing the microphone array along an extended line from the sidewall of the wind tunnel nozzle. Compared with the conventional microphone array installed outside of the main flow, the estimation error of convection distance due to the expanding free shear layer is improved from 60 mm to approximately 10 mm at a main flow velocity of 300 km/h.