Design and testing of sound sources for phased microphone array calibration

Abstract

The phased array technique is a powerful tool for the localisation and quantification of sound sources in aeroacoustic testing. The accuracy of the results is limited due to phase and sensitivity errors of the microphones. A reliable calibration procedure for the microphone array would enhance the applicability of the measurement technique. Currently, appropriate sound sources are lacking, especially for in-flow calibration. An ideal calibration sound source exhibits monopole characteristics and covers a frequency range up to 70 kHz. The present study reviews concepts for omni-directional sound sources and evaluates their capability for microphone array calibration. Two concepts of calibration sources with aerodynamic fairings for the use in wind tunnels have been developed. The radiated sound field of both probes was examined in experiments in an anechoic facility. The presented results comprise the spatial amplitude characteristics of the designed sound sources. In addition, beamforming with a synthetic microphone array was performed to analyse the phase characteristics.