  Mobile robots in real-life settings would benefit from being able to localize
sound sources. Such a capability can nicely complement vision to help localize
a person or an interesting event in the environment, and also to provide
enhanced processing for other capabilities such as speech recognition. In this
paper we present a robust sound source localization method in three-dimensional
space using an array of 8 microphones. The method is based on a
frequency-domain implementation of a steered beamformer along with a
probabilistic post-processor. Results show that a mobile robot can localize in
real time multiple moving sources of different types over a range of 5 meters
with a response time of 200 ms.
