I've mentioned on a similar thread that our issues are not nearly as bad as they once were, but our DS7 with Asperger's still has anxiety about loud sounds. What we learned with him is that volume alone was not the real issue. He actually enjoys hearing a pipe organ. His problem was with noise that was chaotic or unexpected. Loud music was fine because there were no real surprises. A clap of thunder or glass breaking, though, can set him off. For vacations, our greatest resources have been online videos. You can find videos of the fireworks, the horn, the lifeboat drill, and, yes, even the toilets flushing. We can introduce these sounds in a controlled-volume situation that helps with desensitization and letting him know what to expect. When he hears the noises on the ship, everything is exactly as he expected it to be and we have not had any problems.