Interior noise

[Grafton]

Huffer I ask for your audio based wisdom

now that I have a little guy I feel like the interior of my car is a little too loud mainly from the exhaust, and I really don't feel like redoing the exhaust ( currently OBX EL header -> "Busted" Hiflow cat -> obx resonator -> 18" resonator -> vibrant axle-back with 2.25" custom stainless piping ) I've noticed that when I had my trunk STUFFED with groceries and the wife in the back seat (with the baby) the car seemed quieter but from other trips, if i just have passengers in the back seat the car sounds louder.

I know my ears aren't a replacement for a good dB meter but is there anything dynomat and some good closed cell foam could do for me?

if i were to go this route where and how much of the stuff should I apply?

and If the projected cost is going to go over ~750 I'll just a new exhaust from the heads back...

suggestions?

[harrymaneuvers]

I am no Huffer, But I did just do this to my car.

The places that I felt like it made the most impact were:

The door panals, there are a few different "hollow" areas in each door that if covered, eliminate a good amount of noise.

The rear deck where the speakers are. I put the sound deadening material both on the top and the bottom of the rear deck. This one made a HUGE difference.

And although I didnt have time to do it, putting it up against the firewall under the kick panal would have made it a little better.


Past that you are looking at doing the roof and the a, b and c pillars. It is interesting to note that the C pilars actually have a strip of foam rubber under the trim that is put there by the factory... I assume for deadening purposes.

I used this stuff because a local specialty car audio shop uses it and would sell me some off of their bulk sheets... it was maybe $110 to do 4 doors and the rear speaker deck. Wear gloves when working with it because the thick aluminum backing is sharp as hell once you cut it.

https://sl-i.net/FORUM/images/imported/2011/08/41Mu4LJB94L_SL500_AA300_-1.jpg

[Huffer]

Huffer I ask for your audio based wisdom

now that I have a little guy I feel like the interior of my car is a little too loud mainly from the exhaust, and I really don't feel like redoing the exhaust ( currently OBX EL header -> "Busted" Hiflow cat -> obx resonator -> 18" resonator -> vibrant axle-back with 2.25" custom stainless piping ) I've noticed that when I had my trunk STUFFED with groceries and the wife in the back seat (with the baby) the car seemed quieter but from other trips, if i just have passengers in the back seat the car sounds louder.

I know my ears aren't a replacement for a good dB meter but is there anything dynomat and some good closed cell foam could do for me?

if i were to go this route where and how much of the stuff should I apply?

and If the projected cost is going to go over ~750 I'll just a new exhaust from the heads back...

suggestions?

:lol:

Funnily enough I had my interior apart last night and was rethinking my sound deadening approaches. Over the last week I've had plenty of time to research some ideas.

Here's how traditional sound deadening works - you layer up on tons of deadening material and slap it all over the place, and it sounds much better but it's still not that quiet. What went wrong? It's how the deadening is applied and what materials are used, and where they're applied.

First of all, sound is energy. That's it. It's vibration of molecules in the air - no particles in the air (ie. oxygen, water, matter), no sound.
But we can't have the baby in a vacuum, that's not right.

The reason that the interior is quieter when the trunk is stuffed with material, you have actually added a deadener. It's the same as filling your car with a bunch of blankets and coats.

Another issue is that you have road noise coming in from the sides and the bottom of the car. The roof is actually not that big of a deal as it's quite rigid to protect occupants in a rollover. It's the crushable parts that flex the most.

One way of dealing with the side panels is to add a layer of dynomat or other similar adhesive deadener to the INSIDE of the door - not just around the speaker, but to the actual outer skin (if you were to put your hand inside the speaker mount you can tell that it's a massive cavity that acts basically like a sub woofer enclosure. I've contemplated using spray in expandable foam to fill the cavity but I'm not sure what else is in there that I might need to get to at some point. If you can protect things like the door handle levers and any electronics from the spray, and then cover any holes to prevent the foam from expanding out, then you could use some expandable foam. Even packing peanuts would work. Adhesive deadener material (Dynomat Xtreme or similar) would work but it's $$$ and can become very heavy.

You could test my approach by using wads of old newspaper or the packing peanuts - I wouldn't want you to get p'oed at me for telling you to use expandable foam.

Tinted windows actually help - they help the glass from vibrating - not a lot, but every little bit counts. Make sure the seals around the windows are in good shape.

The bottom of the car is tough - it's already lined with deadener from the factory, but with our modified exhausts, harder suspension bushings and lower ride height the car becomes a magnet and a producer for sound. It doesn't hurt to check if the factory sound deadnening has chipped off under the car - and you can buy rubberized deadening spray that can be used in multiple light coats to recover those areas. Sound works like water - it'll creep in wherever there's a gap.

Now for the trunk. The rear seats are usually pretty good at insulating from sound. But as everyone with a subwoofer knows, they don't do as good of a job as we think. Normally people try to put sound deadening (adhesive kinds) allover the trunk lid, sides and under the spare tire. The problem is that the trunk, unless it's filled with a lot of stuff, acts like a big bass box. So how do you solve it, you can't exactly drive around with it filled the entire time. Here's what you have to do - you have to reduce the amount of sound that bleeds through into the cabin. The rear seats.

So how do you stop noise from coming in via the rear seats? Well an obvious solution is a solid wall. Not exactly practical though if you want to still be able to use the fold down or passthru function. So, you need to build some kind of removable sound barrier that can be inserted between the rear parcel shelf, and the trunk floor. Ideally this should be a non-permeable barrier. Alternatively you could place sound absorbtion material (deadener) on the back of the seat and see if that works out.

Just some ideas, nothing definitive. Good luck!

[Grafton]

I believe I have a pan of attack:
Sound deadener + closed cell foam on outer door skin
Extra layer of padding under the carpet
Sound deadener and foam in the trunk

[Baddog]

My sound deadner under my carpet was wet so I removed it. I am going to try and get "fatmat" off ebay. I read some pretty decent things. I just mainly want to use it to help with rattles in the doors and a little deadning from the exhaust.

[Wiscon_Mark]

Raamat Extreme is really good stuff too. Much cheaper than Dynamat Extreme and almost as good. I wish I could find the writeup somebody did where they tested all of the major sound deadeners. If I find it, I'll add the link here.

[ScaryFatKidGT]

If ur worried about his ears I cant believe ur exhaust is over 85DB inside ur car it would have to be LOUD! but you probably want it quieter anyway.

+1 HUFFERS BABY VACUUM BALL!