Differential microphone arrays for the underwater acoustic channel

Design of underwater acoustic sensing and communication systems is a very challenging task due to several channel effects like multipath propagation and Doppler spread. In order to cope with these effects, beamforming techniques have been applied to the design of such systems. The broadband nature of acoustic systems motivates the use of beamformers with frequency-invariant beampattern. Moreover, in some cases, these systems are limited by their physical dimensions. Differential microphone arrays (DMAs) beamformers, which have been used extensively in recent years for broadband audio signals, may comply with these requirements. DMAs are small-size arrays which can provide almost frequency-invariant beampatterns and high directivity. In this paper, we present a pool experiment which shows the compatibility of DMAs for the underwater acoustic channel. Additionally, we show how to compensate for the array mismatch errors leading to much better performance level and robust beamformers.