Microphone localization with self calibrating acoustic GPS

Abstract

The exact positions of microphones are mandatory when using them as an array to apply beamforming algorithms. Nevertheless to obtain these positions in the three dimensional space is challenging. In this paper, further developments of the acoustic calibration unit, proposed in 2009 by Lauterbach are presented. The acoustic calibration unit consists of several speakers and a reference microphone to obtain the positions of an arbitrary amount of target microphones via triangulation. These calculated positions is not necessarily the geometric position of the microphone, it is the acoustic position, which includes possible phase shifts, directivity and mounting effects. In the new acoustic calibration unit a second reference microphone is installed to measure the actual speed of sound. A new triangulation algorithm was developed to reduce the uncertainty of the known reference positions. Furthermore the new acoustic calibration unit was tested on an traversed array with 16 microphones in an anechoic chamber and the open jet array of the ONW-LLF Windtunnel with an diameter of about 4 m. In the final paper a third measurement will be included with an array where the geometric microphone positions are known within a tolerance of 1/100 mm.