Close-talk headset microphones have been traditionally used for speech acquisition in a number of applications, as they naturally provide a higher signal-to-noise ratio - needed for recognition tasks than single distant microphones. However, in multi-party conversational settings like meetings, microphone arrays represent an important alternative to close-talking microphones, as they allow for localisation and tracking of speakers and signal-independent enhancement, while providing a non-intrusive, hands-free operation mode. In this article, we investigate the use of an audio-visual sensor array, composed of a small table-top microphone array and a set of cameras, for speaker tracking and speech enhancement in meetings. Our methodology first fuses audio and video for person tracking, and then integrates the output of the tracker with a beamformer for speech enhancement. We compare and discuss the features of the resulting speech signal with respect to that obtained from single close-talking and table-top microphones.