IMO, one of the worst sounds one can hear is the vibrating of someone's closed trunk when they have a nice system inside. How much do dynamat and other sound deadening devices help when it comes to easing this noise?
its the difference between the cops pulling you over and giving you a ticket for excessive noise (Florida) or being able to smile and wave at the cop beside you because you side mirrors are flapping like a bird from your system and there's nothing he can do about it (windows up of course)