Something repeated happens again and again and again. A dog's repeated bark, unfortunately, is a sound that is continuous — and probably keeping you up at night.
A repeated sound goes on and on: honking a horn just once isn't what this word is about. If you honk that horn over and over, it can be described as a repeated honk. In music, many sounds are repeated as well. The repeated beat of a reggae band is pleasant, while repeated non-musical sounds — like dog barks and annoying people who say the same thing over and over — get less and less fun the more they're repeated.