I'll say what I said on the other thread. Complain to the festival management, but above all complain(in a friendly fashion, it's not their fault) to the performers. They want peopleto enjoy their performance, and they don't want you walking out.Performer pressure on management is the way this problem can be solved. And it is a big problem, both from the point of view of enjoyment, but also the serious question of hearing damage, to punters and musicians...not to mention the sound personnel themselves.