Sort of Sound Advice

(originally published in British V8 Newsletter, Volume X Issue 3, September 2002)

by: Barrie Robinson

I get carried away sometimes and spend far too much time "researching". I constantly battle with getting back to the basics of building my MGB GT V8 instead of exploring all the possibilities out there. Incidentally, I have found the aircraft industry a gold mine of exotic products. I have now some fantastic anti-seize, anti-rust and anti-anti stuff to say nothing of incredible fasteners. My prop shaft bolts are those used on helicopter blades, rated at ten-gazillion sheer force. Not only that, but a paint-on liquid that they use for aircraft exhausts which acts just like a ceramic coating.

At the beginning of my madness several things about the building of a MGB GT V8 gave me cause for thought. One was cooling and after much thought this was solved with a D&D Fabrications heavy duty radiator, a specially shortened water pump, a Perma-Cool 2,950cfm puller electric radiator fan, and a beautiful stainless steel through-the-fender Australian exhausts (which I now sell).

The other area that needed some ponder was sound (as in noise). Now I am not an armchair driver who wants to only hear the clock ticking and I do like to hear the engine growl. Neither am I one of those people with the intelligence quotient of a piece of burnt toast that spend thousands on "hi-fi" systems for their cars. That's like wearing a Saville row-suit in a hot tub. So I did some looking around. Naturally the first stuff that took my eye was Dynamat and after that some other similar products.

The first thing that puzzled me about these products from Dynamat and people like B-Quiet was that the aluminum foil was on the wrong side. So I phoned a supplier and had a conversation with a "technical person". My argument was that if the product was to reflect the heat of the sun out of the car then this should be next to the metal of car's body. So from the outside it should be car body, adhesive, aluminum foil, rubberized bitumastic/polymer stuff or whatever (technically called the "goop"). The "technical person" said no, the heat went through the car body, through the goop, reflected off the foil, back through the goop and out. This I found somewhat nonsensical and reasoned that the product was obviously not designed for sound deadening in automobiles.

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Well, it turns out that this is, in fact, the case! The product is nothing more that roofing material as used by construction people. It is readily available in a variety of sizes and types from your local roofing contractor at 1/10 the price. As to the goop, your schoolboy physics will remind you that there is little difference between them all you want is mass! Just get one that stands up to the heat, and they all do! Also do not get excited about the aluminum foil. Just because it keeps roofs cool by reflecting sunlight does not mean it will be as effective in the dark. If you have a resonating panel it is easily stopped by putting your hand on it. It kills the vibration. So just imagine your hand being replaced by a patch of something, something like rubberized bitumen! By stopping the vibration of the panel you stop the drumming, thrumming, and rumbling.

Now this goopy stuff is great for deadening "drumming" panels and is great indoors, wings (fenders), inside gearbox covers (inside is better than outside for heat) and on floors (particularly on boot floors). The material is easy to use. The adhesive under the peel back paper is great and it molds reasonably well with finger pressure.

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However, there is also the high pitched sounds and those squeaks and buzzes. For this closed-cell foam is good. It has to be closed-cell so that it does not soak up and hold water. The little air pockets help stop sound as well as adding heat insulation in both directions. So I have put roofing stuff in my doors, roof, back panels and all sorts of places. But I also have used specially manufactured (in Toronto) closed cell polyethylene foam. The problem was sticking it to the foil of the roofing stuff - remember the foil will be on the inside and exposed. I tried some highly recommended 3M products, floor tiles stuff, but nothing really worked. Then I discovered Zytek A8411 the wonder contact glue. It is expensive, easy to apply and locks on like a leach but as it cannot be shipped without special arrangements, like other funny chemicals, I had a hard time getting it. But get it I did, and work it did!

As a result of this fevered activity I have decided to offer my new wonder sound deadener. It is a combination of rubberized bitumastic material with foam bonded to it. It provides low frequency dampening with rubberized bitumastic, high frequency dampening with closed cell foam, and mid frequency dampening with acoustic pockets sandwiched between the two layers. Cost is $5 per square foot with minimum quantity of 10 square feet. It comes in pieces 6 inches by one foot allowing easy application. It requires no glue and has adhesive under a peel back waxed paper cover. The construction of the material is shown in the accompanying diagram. It is quite stiff so getting it in a door may require some sweat and mumbling, to say nothing of cutting. Not recommended for bonnets (hoods) and ideally suited for the inside of firewalls, doors, body cavities. I will supply just the rubberized bitumastic (Dynamat type) material for $2 per square foot (minimum 15 square feet). The minimum quantities will just about do an MGB GT. Please send any questions to:

Disclaimer: This page was researched and written by Barrie Robinson. Views expressed are those of the author, and are provided without warrantee or guarantee. Apply at your own risk.

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