Low power beamforming for underwater acoustic sensing using a 5-element circular hydrophone array

In this paper we present a technique for underwater acoustic beamforming based on soundfield recording that encodes both the temporal and spatial characteristics of a signal. Here, we introduce the basic theory behind soundfield recording and present a first-order beamformer that beamforms the encoded data in a specific direction (θ,φ) and with a variable polar pattern, p. The appeal of this beamformer being that a 2-dimensional beam can be created using only 4 multiplications and 2 additions. A method for implementing a wideband, planar soundfield recorder using a 5-element array is then discussed. Results from underwater experimental trials using this 5-element array are then presented that compare the measured beam patterns and frequency response of the physical beamformer to the ideal, theoretical beam patterns and frequency response.