Detection of broadband sound sources using a randomly spaced linear array

Arrays are commonly used in relatively narrow band applications. The array design and processing are usually optimized in order to maximize the gain in the look-direction, while minimizing the interference from sources located in other directions (but possibly not far off from the look-direction). This led for instance to the definition of minimum redundancy linear arrays that maximize the resolution for a given number of sensors. This maximization is, however, effective only at the design frequency of the array. For many active applications (such as active sonar or radar), which are narrow band in essence, this limitation is not an issue. However, if the signal to be detected in its entirety has a broadband frequency content, optimizing the performance of the array at a given frequency leads to possibly poor performance at other frequencies. Since optimal performance cannot be achieved at all frequencies simultaneously, one can aim for sub-optimal but useful performance throughout the entire frequency band. One possibility for achieving this is based on the use of a random hydrophone spacing. The effectiveness of the approach is investigated using simulations and is illustrated with experimental data collected using a randomly spaced linear array.