Originally Posted by Dwight Frye

I have thought about this: there is a stretch of freeway that I travel that has various surfaces and really plays a symphony, or rather cacophony with the tires. The thing to do would be to use a recording measuring device and travel a certain section of road, long enough to get a good reading. Maybe 10 miles. Stay in one lane, at one speed as much as possible, A/C and stereo off & windows up. Take a measurement maybe every 10 seconds with the microphone in a fixed location, like attached to the inside driver side headrest strut. Install the Dynamat & repeat the test. Print out the graphs or plots and look at the difference in SPL at the same locations and elapsed time. There you go.