I don’t think the Steelers made a formal complaint, but some players definitely mentioned the practice of piping in extra sound at Indy.
I heard on WEEI that there was also a problem with QB to coach communication.
I’ve heard a few teams complain about it, but this is the first time that something has happened that could be evidence (the tape sure sounds funny). Of course a lot of folks complain but write it off as gamesmanship, everybody seems to do something to annoy visitors, especially dome teams. I remember a few years ago there was a minor to-do because the Vikes put huge speakers suspiciously close to the visitors bench making the most basic sideline communication difficult. And that’s just the NFL, NHL fans might remember the tale of the Colorado visitors bench which eventually resulted in the Wings bringing their own park style benches and yanking out the ones in place, then there’s the humid baseball thing, and which college team painted the visitors locker room pink. They don’t call it home field advantage for nothing.