How about trying to reduce the louder sounds that interfere with how we hear ourselves? I've talked to symphony players that have plexiglas shields (much like police motorcycle windshields) mounted to the back of their chairs. I know that only takes care of sound from the back, and it's probably more gear to lug around than desired....but just a thought. Perhaps combined with the other suggestions, we could achieve the desired results. For acoustic situations, I prefer acoustic solutions. For amplified situations, I prefer electronic solutions.