I wonder how it would sound on SONAR?
Not only would it make a huge swath of sound, surely easily detectable by even a child with an empty soup can and waxed thread, it would likely be acoustically blind to everything around it. All its underwater sensors, sonar, fathometer, etc. would be incapable of "hearing" anything.
So what do you end up having? A submarine that can get from point A to point B in a hurry, all while announcing its presence by anyone with any sort of underwater technology. Once that submarine is at its "point B," it still has to go into whatever its "stealthy" mode is, and do what submarines are supposed to do.