I found this interesting little tidbit on a site about the Navy's ARCI sonar improvement program:
"Specific software improvements included passive ranging, spatial vernier processing, full spectrum processing,
dual towed array concurrent processing, low frequency active interference rejection, passive broadband, passive narrowband and passive detection and tracking processing, track management, on-board training, and port/starboard ambiguity resolution."
http://www.defenseindustrydaily.com/...ated/index.php