The idea of applying the microphone array technology for machine condition monitoring of a mine site has been investigated at the University of Western Australia. As a key part of the investigation, this paper focuses on the sound source localisation and signal extraction using the beamforming technique. Instead of a single large array, multiple small arrays are used, as practically, they can be easily deployed. In terms of array processing, they are normally processed as independent arrays. However, with synchronised sampling they can also be processed as a single combined array. These two processing approaches are termed the independent array approach (IAA) and the synchronised array approach (SAA), respectively. The main advantage of SAA is its greater array gain and higher beam resolution. However, the arrays need to be placed close to one another to avoid producing aliasing lobes. The IAA on the other hand has no such restrictions and the arrays can be placed independently in any position. This may provide gains in signal to interference and noise ratio (SINR) for individual sound sources in certain circumstances. In order to compare the performance of the two approaches under various conditions, numerical simulations are carried out. The performances are evaluated in terms of the accuracy of source localisation and the fidelity of signal extraction. The general guideline for using the two approaches is provided.