I have been doing some reading on U-484's sinking on 9/09/44 and the ensuing controversy crediting the kill first to the RCN and then later the RN. In reading an account by a seaman on the corvette HMCS Hespeler that described the search for evidence of the sinking, I wondered why ASDIC and/or sonar wouldn't have helped confirm the tragic event. U-484 (or something else) was being tracked by the Hespeler's partner, frigate HMCS Dunver's ASDIC. In short, if submarines constantly need to be quiet to remain elusive, I wonder why a catastrophe such as an imploding pressure hull, screams, etc. wouldn't make one hell of a blip on the screen. Or does it not work that way?