Acoustic beamforming: analysis of uncertainty and metrological performances

In this paper, the metrological performances of the acoustic beamforming technique have been investigated, and in particular, its accuracy in estimating the acoustic power of sources and in localizing their spatial position has been analysed. The uncertainty of the system has been determined combining the statistical effects of input parameters uncertainty under the basic hypothesis that the sound source can be represented as a distribution of independent monopoles. This analysis was performed using a Type B approach based on an analytical model according to the ISO Guide of the expression of uncertainty in measurement and subsequently using a numerical model based on Monte Carlo simulation. Systematic errors due to deviations of input parameters (e.g. speed of sound or source–array distance), affecting output level and spatial accuracy have been analysed. Once these inaccuracies were quantified, suggestions to minimize them were given. Finally a criterion to optimize focussing of the beamforming technique based on acoustic image contrast maximization has been developed