How much difference in noise levels do underhood pads make?

[02Pilot]

I have very mixed feelings about adding pads under my hood and trunk lid, but I'm also trying to make the car a bit more civilized (yes, I'm as appalled as you are by this wanton display of maturity), and I've done the basic interior stuff already. For those who have them, particularly the Squatch pads, how much of a difference have you found they make in sound levels inside the cabin?

 

For the record, I'm running dual DCOEs and long-tube headers, so this is not exactly the ideal candidate for being quiet, but I'd rather add some foam than fully capitulate to my advancing years and start ripping out performance parts. I'm old, but I'm not dead.

Edited May 9 by 02Pilot

[Son of Marty]

The hood pads will cut the noise a bit mostly on the outside of the car, I don't think the trunk pads won't add much.

[jimk]

Noise from outside the car enters thru the hood heater/fresh air opening and thru the heater.  Stopping the hood from drumming helps.

[OldRoller]

The squatch foam helps with hood vibrations, a little. Trunk helps very little, inho. but looks good.

Making sure your cross-hood to cowl seal is in good nick (as well as the side seals) cuts a lot of underhood noise. I've got the original air cleaner/weber, so it's fairly quiet.

My left fore/aft hood support ridge was contacting the torsion bar, creating a drone at certain revs. A small foam wedge cured that. 

[SydneyTii]

I’ve been in a car with the whole hood underside done very nicely and I didn’t really notice when driving, it surprised me how quiet it was when I stood next to it though.

[02Pilot]

Thanks for the feedback. It doesn't sound like adding the pads is going to do all that much. The cowl seals are fine, so no easy fix there.

[TobyB]

There are several ways to listen to this:

if you're objectively listening to levels inside the car, it's

not going to make much difference (at all) in loudness (dBSPL)

 

If you're subjectively listening to levels inside the car, damping every

resonant contribution, even if it doesn't affect overall level,

is going to make the car less dissonant.  Less fatiguing.  More solid.

Fewer out- of- time contributions.  We weren't evolved to be comfortable

when there are lots of discordant sources of noise.

 

And there's something satisfying about a trunk that closes with a clunk

rather than a 'boing'.

 

t

boing used to make airplanes...

[Mike Self]

What will make a significant difference in cabin noise is good padding under the carpet (think household carpet padding) including the tranny tunnel, and something in the void under the back seat.  It could be sturdy bags of styrofoam peanuts, chunks of closed cell foam packing or even thick pieces of styrofoam packing cut to fit.  then hang a piece of carpet padding from the two hooks that hold the rear seat back and you'll notice a lack of booming and resonance with that void filled up.

 

mike

[02Pilot]

I understand the basic principles of sound deadening - I probably should have explained what's been done so far. When I reassembled the interior, I sealed the firewall, selectively used Kilmat on large, flat panels, laid down a layer of MLV on the entire floor and up behind the back seat, put down carpet padding over that, filled the voids under the rear seat and behind the rear trim panels with rigid foam insulation, and redid the door panels with the Turtle Labs plywood cards. It's definitely improved over what it was prior, just looking to see if there are any more easy gains to be had.

[OldRoller]

2 minutes ago, 02Pilot said:

should have explained what's been done so far.

You done quite a lot so far. The hood pads will reduce the intake/engine noise some, and the trunk foam may reduce transient vibrations from exhaust and diff operational noise. 

Given the length you've gone so far, might as well carry the efforts on. 

One benefit of the Squatch hood foam I've found is the temp of the hood surface after a run, shutdown and hot soak. Much cooler to the touch. 

[Vicleonardo1]

I went down this rabbit hole before. Did a lot of research and there are good and bad solutions out there with a range of a using a ton of single vs multilayered pads to just a few strategically placed pads, bricks solid vs filled with water etc. etc. There are methods based on good science and very bad science and it was hard for me to develop a strategy. 

It looks like you have done a ton already that I am not sure what else you could do aside from the hood and trunk pads is work on deadening underneath the headliner. Which also has too many good vs bad options to try out. 

But the engineer guru's here like Toby will give sound advice....pun intended. 

 

Bottom line what you will do is add weight to your 02' but you will never acheive  luxury car silence. I just need enough deadening to let me hear and sing to my portable bluetooth speaker....which is a very different form of sound pollution. 

 

Cheers! 

VL 

Edited May 10 by Vicleonardo1

[02Pilot]

Yeah, I know it's never going to be quiet; I'm just looking for less-loud. The weight is definitely a consideration, but the MLV is really the only thing that weighs much. I used the 1/2lb stuff, which isn't too terrible for weight - I didn't both calculating the square footage, but there's a lot left on the 30sq ft roll I bought. I figure I probably added ~50lbs total at most, and it's all down low.

 

The headliner needs to be replaced at some point, but that's not happening any time soon, so that remains an unexploited opportunity for further reduction.

[2002FjordBaur]

Not as factory... but fully covered.
Don't think it's made any difference to engine noise intrusion, but I rarely drive with the roof on, so wind noise normally hides any scary sounds the car may make!

[Son of Marty]

I'd start shopping for a factory ti air cleaner it'll tame the intake noise quite a lot.

[02Pilot]

14 minutes ago, Son of Marty said:

I'd start shopping for a factory ti air cleaner it'll tame the intake noise quite a lot.

 

 

I've already got one, though I'm running it without the end caps due to clearance issues at the firewall. I'm going to attempt to resolve the remaining problems this summer and try it with the caps.