Toward intelligent sensors - reliability for time delay based direction of arrival estimates

Increasing demand for automatic large area surveillance has made methods estimating direction of arrival (DOA), especially acoustic methods, an interesting topic. In these systems false alarms and faults are a disturbing factor. This paper presents a reliability criterion and a new method to diminish these errors. In very low signal-to-noise ratio conditions there are seldom any means to improve the performance of a DOA estimator. In these cases it is important to have some information about the estimation reliability. Our focus is on wideband signals propagating as planar waves in three dimensional space. If the estimation method makes no assumptions on the signal propagation speed, it is possible to compute a reliability measure for obtained estimates. With this reliability measure we are able to decide whether the data produced by a time delay based DOA estimation system is usable or not. Indeed, with this criterion an estimation system can state its own reliability.