A couple games ago, I was laning vs a Katrina. She used her ult, etc setc, but the sound never went away.
It was sort of like the audio version of how sivir's blade is sometimes just randomly spinning in the air, but infinitely more annoying.
It was also area speciic, e.g. it was only there why i scroled over that part of the map, it faded correctly as i scrolled away from it.

I have heard this too when in a game against a Katrina. It does seem localized to one part of the map, but every time you scroll over it the sound starts. No idea how to duplicate it, but it's annoying.

We will be adding a possible fix for this in the upcoming patch. If you guys experience the problem again after that, please post it on the boards so we know we need to keep working on it.

Thanks!