FATmat, DYNAmat sound deadening and heat shielding : MG Midget Forum : MG Experience Forums : The MG Experience

"Does this really make the car all that more quiet?"

that is a good question, because there isn't much incentive for folks to do a whole lot of trials with it (how many times do you want to remove your interior?), so they usually just cover everything and cross their fingers. Often, it is accompanied with a new interior, so it can be hard to tell which was the source of any actual improvement.

The downside is the added weight (it can add up to a LOT), and, in the worst case scenario, if water was caught it could cause rust pockets.

The upside is possible quietness, or, at least, more solid feeling by eliminating resonance from panel vibration.

Here is the thing, OEMs, who struggle monumentally to achieve the highest levels of quietness in their cabins, they end up using a surprisingly small amount of the stuff (it looks a little different because it goes in during body weld, before paint, but does the same thing).

Generally, an OEM will find the resonant point in a panel, and then put a little patch of the stuff right there.

Experiments have shown that, in general, adding more than that does not make much more improvement.

A big exception can be when using a super high-power audio system, when you need everything in the cabin to be as dead as is possible. But, I don't think that's the case for most of us.

Some years ago, I was responsible for the interior and exterior trim for the last Oldsmobile Cutlass convertible, and we were struggling with cabin noise inside, with the top up. It was driving me nuts, as we tried many, many options and variations on each theme (the top was lined, and was supposed to be pretty quiet, but too much noise was coming from the road/tires/underbody). Well, I finally asked for every inch of the interior to be filled with all of the options (stuff like fat mat, plus shoddy rag (loosely battened stuff that absorbs high frequency noise), and so on). We filled it with way more than could ever have been done in mass production. The result? No noticeable change.

So, we went into production with relatively little additional soundproofing, because we had proved that it didn't make a significant improvement either way.

I suspect that our '60s convertibles will be somewhat similar to that experience.

Norm