Hm, that’s really odd then indeed. Do you have on other lttp rom to try, maybe the rom is faulty, since it’s not occurring in other games as you said. I’m also playing lttp here on a b+, with retropie 2.3, without issues.
I read you’ve got a rpi2 so this afternoon I tested it on my rpi2 also to try to figure things out for you, but I haven’t got static.
One thing I do have, or better said, I don’t have, is music in the 1st room inside the castle. There should be music playing, but the music stops as soon as I enter the castle (via the little shrub).
Then, after going through the first door in the castle, music re appears and everything seems fine.
Tested this out, but this also occured with 2.3 on the b+, so there indeed can be something not 100% right in the rom itself.
Anyway hope you do have sort of an idea cause I can’t really try more from here. O, by the way, only sound settings in retropie I’ve changed from default is sound from 48kHz to 41kHz. Can try that too, does hurt if you do.
If you do not have another game to test I maybe can help if you want, send me a private message if you’d like any help with that.