Influence of various uncertainty factors on the result of beamforming measurements.

Abstract

In a previous publication [Mller-Trapet and Dietrich (2009)], a virtual measurement environment for sound-source localization on vibrating structures was presented. Based on surface velocity data obtained from laser-scanning-vibrometry measurements, the boundary-element-method is used to simulate the sound radiation from a vibrating plate toward a microphone array under ideal conditions. The advantage of this approach is that the measurement conditions can be perfectly controlled and real sources can be considered, without restrictions on the type of source. The virtual measurement environment will now be used to investigate the effect of some of the uncertainties that can be encountered during beamforming measurements. For the most common planar array geometries, the beamforming source maps will be calculated for varying signal-to-noise ratios and different array imperfections (uncertainties in the location of the microphones and deviation from the omni-directional directivity pattern of the microphones). As a measure of comparison, the two-dimensional normalized cross-correlation between the ideal source map and the source map with added uncertainties will be evaluated and discussed.

On the in situ impedance measurement with pu-probes—Simulation of the measurement setup

“…15 is used to precisely reproduce the situation of an in situ measurement while being able to perfectly control all uncertainty factors. In order to achieve this, the entire measurement setup and procedure is simulated with the help of the boundary-element-method (BEM), where the geometries of the loudspeaker, pu-probe as well as the absorber and possibly other surrounding reflecting surfaces can and will be taken into account.…”