HF active is detectable depending on your sonar setup, really just all depends on what sensors you have. And also keep in mind that even if a sensor can't hear it, the submarine might be able to. For instance: You have a submarine that only has a low-freq passive array out and can't hear the mid-freq stuff, but a surface ship goes active on you in the mid-freq level at 200+ db. The entire crew is going to hear it, and they know they've been found
(Note: Above situation obviously isn't real, and isn't using exact / close to exact numbers~)