Application of a linear microphone array for noise source detection in the CIRA calibration tunnel No.2 (CT2)

摘要

This paper describes the use of a linear microphone array to detect noise sources m a small open jet wind tunnel. The objective was to assess the capacity of the array to identify sources in the test section and to develop a measurement methodology appropriate for this. The tests were performed in a small, low speed, open jet, calibration tunnel at the Experimental Aerodynamics Laboratories of CIRA. The source was effected using a small loudspeaker placed in different positions along the tunnel centreline and the localisation was attempted with and without flow in the test chamber. Results show that in the absence of flow, the system correctly identified the source location indicating that the environment external to the tunnel had no great influence on the measurement procedures. The experiments performed in presence of the flow confirm the reliability of the technique, but reveal some difficulties in detecting the source at frequencies corresponding to high noise emission by the tunnel diffuser entry section. Test results have indicated how the tunnel should be modified to improve the sensitivity of the array measurement technique.