Blueboy has a fair amount of dynamat layered in him as it was installed when the Rover was stripped to bare metal.
it certainly helps, yet, I can't hear my cell phone ring and forget about talking on it especially during the warmer months with the windows and front vents open.
my wife and I can hear each other though very well when we talk with the windows closed, so there is some noise reduction with it.
depending on how far you want to go, it may or may not be worth it especially if you drive with the windows open most of the time.
Jaime