Passive and active Sonar applications for a nonuniform and low cost Linear Array

one of the reasons to use a non-uniform linear array (NULA) is to reduce the cost and complexity of the array, since it can have fewer sensors than an ULA system. In this paper, authors describe the construction of a low-cost, ten-hydrophones, nonuniform linear array to be employed in passive and active sonar applications. Many experiments were conducted, under controlled conditions (large pool), oriented to characterize both individual transducers as well as the complete array. Using the array in “passive” mode, employing an omnidirectional sound source and a non-impulsive signal, beamforming and inverse filtering techniques, the authors evaluated array directivity over a wide range of frequencies (1-23 kHz) and also its capability to estimate the direction of arrival (DOA). Furthermore, this work also focuses on searching objects and identification. Different test were performed, in order to estimate system performances when used as the receiver of an active sonar. Using sine-sweep signals, and a specific real-time software developed by the authors, several measures were conducted in the shallow and very shallow water showing the ability of the system to detect objects in a 45° wide angle.