Air Presure

[Sharp_Shoota 10+ year member]

Ok my trunk ratles like crazy even after I coverd the whole thing in dynamat. However today I noticed if I sit in the car witht he dorrs / windows closed and turn the system up it rattles realy loud but If I open a door or the windows it doesnt rattle no where near as bad.

The only logical explination I can find for this is maybe opening the door or window decreases the sound pressure in the car so the woofer isn't forcing so much air / presure onto the trunk to make it rattle?

If this is the case then the ultimate way to stop a trunk from rattling which seems to be a common problem would be to maybe add some vents / air grills in the trunk door? or simply drive around with the windows down?

Or am I just talkin' crazy again, hehe?

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[mattj 5,000+ posts]

The pressure is created more than it can be released so your car basicly flexes out and it can only do so much and obviosuly metal is going to give back hence you get rattle. You will not eliminate 100% of your rattles but cover the holes in the trunk as best as you can and make sure it has a good solid connection from deadner to metal.

 

[ssj2xxgotenxx 10+ year member]

The pressure is created more than it can be released so your car basicly flexes out and it can only do so much and obviosuly metal is going to give back hence you get rattle. You will not eliminate 100% of your rattles but cover the holes in the trunk as best as you can and make sure it has a good solid connection from deadner to metal.

Too add a little, make sure you have good deadener. Not sure but dynmat original isn't that great of stuff Xtreme on the other hand is pretty good; try and add another layer or two on the areas with most rattle.

 

[PopcornPlaya 10+ year member]

look around in your trunk, tap places, and if they have resonance, add more dampener. also, you can use expanging foam in areas where there is space between metals. another thing you may want to look for is, in a lot of the newer cars have an air vent/flap inside the trunk. usually it has a rubber flap in there, and it lets air in and out of the trunk. you might want to do something about that if your car has one. i took mine out of my 2001 civic, and fiberglassed over the opening, it took out a lot of rattles. you might also be able to move your trunk latch slightly where it'll close tighter. again, i did this in my car, and it helped alot. another thing you could check, if your tag is mounted on your trunk lid, as mine is, is to add a layer of dampener to the back of your tag. also, you might want to try adding dampener to panels inside the car's cabin. i did this as well, and have another 100 sq ft. of dampener on the way to do more (doing another layer in my trunk, and as much as i can get through for the second time in the cabin.

 

[Sharp_Shoota 10+ year member]

The problem with my trunk door is it has a peice of plastic covering screwed onto it so i took this off to put dynamat onto the metal door but its not a smooth surface, its very shaply this is hard to explain but instead of a sheet of metal it has bumps and kinks all over it where different things fit into or onto to it so It was very hard to cover it all.

I was woundering where can I buy some expanding foam to fill the gap between the metal and plastic cover?