Acoustic imaging in turbulent media with the spatial bispectrum

A new array processing system that performs high‐resolution imaging in turbulent ocean media is introduced. It exploits information contained in higher‐order spatial spectra and images to a resolution which is limited by the array aperture rather than the medium. Precise a priori knowledge of the turbulence’s spatial coherence structure is not needed. Furthermore, the signal processing is straightforward to implement, the system is self‐calibrating, and the computational demands are reasonable. Initial tests of the imager have been conducted and several representative examples are presented. It is found that precise bispectrum estimates are required for good image quality. Since this requires large data sets, in essence this algorithm trades data requirements for resolution. In addition, the direction of arrival information, contained in phase terms that are processed with the bispectrum, is lost in the averaging process. Nevertheless, the system provides very good quality images, even in severe environments.