Directional microphone array for security applications

Abstract

This project investigates the potential for microphone arrays within a security setting, particularly through exploiting their ability to change their directivity pattern, thus, changing its direction of hearing. In single microphone systems speech and other signals of interest can be severely degraded when recorded in real environments. Security and surveillance systems are no exception to this rule and therefore microphone arrays have the potential to supplement the range of listening devices already available. This dissertation presents the work covered, which includes: • The potential need for microphone arrays in security settings. • The legal implications of using microphone arrays in surveillance. • The concepts of beamforming and the theory behind three common beamformers, including the Delay and Sum beamformer, the Adaptive Frost beamformer and the Generalized Sidelobe Canceller beamformer. • Tests conducted on the beamformers to determine their performance with different parameters and different types of data. It was concluded that both the Frost beamformer and the Generalized Canceller both have the potential to be used in a security setting. The best performance was achieved with the Frost beamformer with an array size of eight microphones and a tapped-delay length of 131.