47-55.1 *Sound Deadening Material*

[Zippi]

Guys,

I'll be pulling the bench seat out of my 49 and pealing the carpet back to install bucket seats. I'd like to add some sound deadening material but just a quick look online shows it being pretty costly. Has anyone used anything from Lowes that would work just as well?

[joedoh]

remember that there are two sources of sound: direct and sympathetic. direct is air propagated, meaning the thing that creates the sound is within direct earshot and you hear it. sympathetic is based on resonance, meaning you hear something else vibrating sympathetically when it is directly hit by sound. if I sealed you in a steel drum, you could still hear me talking outside because my direct voice would strike the metal of the drum and vibrate, on the inside you would "hear" it even though there is no way the sound waves could penetrate the steel.

knowing that, seal the direct paths: holes in the firewall, floor, doors and door jambs, anywhere that air can leak in.

for the sympathetic paths, you can dampen their sound by lowering the "resonant frequency". big flat panels will resonate, and will do so more at the natural frequency of the panel, a frequency where the natural response is loudest with the least amount of sound. sound deadener works on this principle, adding mass (usually asphalt) to a panel lowers its frequency, and lower frequencies are much harder to reproduce and need a lot more power. ever bought a subwoofer amplifier? much more powerful, much larger. same idea.

adding mass has a finite limit though. once you lower the resonant frequency enough you can stop adding mass, adding additional mass makes things heavier but does not dampen the sound any more. so multiple layers are rarely needed, in fact complete panel coverage isnt really needed. I typically will dampen the flat and thin panels, like the firewall, floor, and trans tunnel, but resist complete coverage. over that but under the carpet I put a thick jute pad, which works on the principle of absorption of reflected sound (in a metal cab with a metal dash everything reflects!). so about a roll of foil backed asphalt roof sealer ($16 at home depot), a jute pad (~$60) and sealing the doors and glass gives me a quiet quiet cab.

[jweb]

I think Joe gave you the perfect answer but I will say the biggest difference I saw was good door seals.

When I first put my truck together I covered the entire inside of the cab with Fatmat and even used 2 layers in some places. I had no door seals and it was still really loud.

When my truck got painted I added door seals and new window felt and there was a huge difference. So I would say make sure everything is sealed up good before you worry about sound deadener. Also close off holes in the firewall if there are any.

Then use the roof sealer and jute pad Joe mentioned.

[Zippi]

Thanks for all the help guys.

[mr48chev]

I had the Lowe's stuff in my 51 Mercury because I couldn't afford anything else at the time and it was just foil wrapped bubble wrap and didn't help a lot. I think you are thinking the denser stuff that comes in smaller sheets though.

The Fat Mat has good reviews an you can order it on Ebay in pieces pretty close to the size you need. It might be worth your time to snoop on some of the audio boards and see what the latest scoop as far as what gives the best results for the buck is.

[Zippi]

I picked up my truck from the muffler shop tonight and the owner showed me some sound deadening material that has the carpet made on it. It's 5/16" thick and is a peal and stick material. He couldn't find the phone number of the local fellow that deals with this but said he would text me his number. Looks pretty nice.

[Zippi]

Well....got my bench seat out last night after work and I pealed a corner of the carpet back and low and behold I say some white matting on the floor. I'll know more this coming weekend as I'll really be diving into this project. I did put the passengers side seat in as I was curious as to just where the front right leg of the bucket set would mount. Of course its right over a portion of the battery cover but I have the gears turning in my head for that issue. Anyway....may not need the floor deadening material after all. I'll know more when I get the carpet out and can take a really good look.

[VWNate1]

One of the most important aspects of this is CLOSED CELL ! anything that will absorb water will cause rusting out as time goes by, BT, DT .

If you add the pads to the iside of the doors, make sure you don't cover any holes where water might get in and always leave at least 1" above the bottom where moisture might collect .

I did my '49 3100 shop truck and added padding inside the roof , and back of the cab as well as both doors and the floor .

It was so quiet inside I added a radio......

Jute padding is nice but it holds water like a sponge so beware of it .

[my56chevytruck]

Originally Posted by Zippi

Guys,

I'll be pulling the bench seat out of my 49 and pealing the carpet back to install bucket seats. I'd like to add some sound deadening material but just a quick look online shows it being pretty costly. Has anyone used anything from Lowes that would work just as well?

Check out CARINSULATION, that is what I used. It does a great job of insulating and sound deadening. And they're great people to talk to.

[Zippi]

Thanks for all the reply's. I have a question. On the bottom of my doors there are the factory drain holes. I have seen and heard from others that some of the sound deadening material uses bubble wrap so would bubble wrap do any good if packed inside the doors to deaden the outside noise? The reason I'm asking is I have access to bubble wrap at no cost to me.

[joedoh]

I think the bubble wrap is used for heat insulation, not sound. closed cell foam works on the principle of sound insulation but its much thicker, so maybe lots of layers of bubble wrap may insulate for sound.

you could always test, wrap yourself in a lot of layers of bubble wrap and have someone shout at you. even if it doesnt work you could jump off the couch and get that satisfying popping sound.

[Zippi]

Originally Posted by joedoh

I think the bubble wrap is used for heat insulation, not sound. closed cell foam works on the principle of sound insulation but its much thicker, so maybe lots of layers of bubble wrap may insulate for sound.

you could always test, wrap yourself in a lot of layers of bubble wrap and have someone shout at you. even if it doesnt work you could jump off the couch and get that satisfying popping sound.

Haha.......that sounds like fun with the grandkids this weekend.

[Zippi]

Ok guys.....Got my new seats in and the floor is sealed. I'm checking for all holes in my firewall and not sure just how to seal this one up. Any ideas?

[raymond0275]

I used Sound Seal Acoustical Pipe & Duct Wrap from lowes, and it works great!(LOL) I could not afford the expensive stuff.

[mick53]

They make grommets for just about every size and shape.

[Zippi]

Originally Posted by mick53

They make grommets for just about every size and shape.

Yeah I've seen a bunch of the grommets. Guess I could split one and work it around all the wires and black loom.

[jweb]

Originally Posted by Zippi

Yeah I've seen a bunch of the grommets. Guess I could split one and work it around all the wires and black loom.

Just cut a slit in a regular grommet or if you want to get fancy order one of these

https://www.summitracing.com/parts/s...CABEgIdWvD_BwE

[joedoh]

I use a flexible sealer for that kind of thing, like liquid nails fuze-it.

your cowl vent tube seems to be missing (hole at the center of firewall), that will let wind air and noise in, and more than that when it rains or in a car wash will let water just pour on your firewall and carpet.

[Zippi]

Originally Posted by joedoh

I use a flexible sealer for that kind of thing, like liquid nails fuze-it.

your cowl vent tube seems to be missing (hole at the center of firewall), that will let wind air and noise in, and more than that when it rains or in a car wash will let water just pour on your firewall and carpet.

Got a pic of how the cowl vent tube is hooked up?

[joedoh]

Originally Posted by Zippi

Got a pic of how the cowl vent tube is hooked up?

sure.

I always use a length of heater hose to route it away from pouring on the engine, then seal around it

[Zippi]

Originally Posted by joedoh

sure.

I always use a length of heater hose to route it away from pouring on the engine, then seal around it

Thanks for the pic. So....I assume there is an area on the cowl vent itself where the tube fits over. Is it a snug fit our is a clamp used? Not much room under the dash as I remember when I installed my radio. Funny they would make an oval shaped hole in the firewall for a round hose.

[Tempest67]

it's oval because it comes out of the firewall at an angle. (aiming down)

[joedoh]

i snug it and use a clamp. the original just snugs.


tempest is right, it comes out at an angle. the worst thing is, that the tube it connects to is only about two inches from the firewall but ends INSIDE, so you have to slide it in from outside but if its missing the water just dumps on the floor.

which could work out for you, if you have limited room under the dash just put some mineral oil on the inside of the tube and slip it in at the right angle, you should be able to push it on far enough without needing to get under the dash. I usually do it from the speaker grille, easier to see, than getting under.

[Zippi]

As always guys......thanks for the info.

[Zippi]

One more thing guys. What's the ID and OD of the tube I need to use? Probably just go to Advanced Auto Parts and pick one up.