I built my car as an autoxer years ago and never installed carpet or sound deadener after the restoration.

Now as I age and have an opportunity to take a longer trip in the car I am looking for a little more "comfort" in the car.

Question is how much will carpet and/or sound deadening improve the road noise?

The back pad has been removed and there is sound deadener and felt covering the firewall currently.

Curious as to what you all might have experienced or recommend.


I am also thinking about dialing back the suspension setup for the long trip.

I believe the sound deadener makes a dramatic difference in our cars. My floor, firewall and doors are all done. Anything you can do to keep heat and sound out is a good thing. (IMG:style_emoticons/default/beerchug.gif)

Duplicate

I have been involved in data analysis and modeling to correlate ride quality with 3rd party quality metrics like Consumer Reports, JD Power, OEM customer satisfaction surveys.

Sound is a highly correlated variable even though it has no direct effect on ride quality. That is to say that most people if they perceive that bumps are “loud” they are also perceive the bump to be more severe than it really is as measured by seat track accelerometers.

So - a quieter car is perceived to ride better than an equivalent car that is noisy.

Addition of constrained layer damping like Dynamat will get you a huge improvement over what you have (nothing). This treatment will reduce the structurally transmitted noise low frequency noise <100 Hz.

Addition of carpet and a back pad over Dynamat will reduce the higher frequency airborne noise above 100 Hz.

You really want both types of noise reduction treatments since they each affect different noise frequency ranges.

Don’t forget the felt liner on the targa top - that big fiberglass panel is a noise reflector.

Dialing back your suspension from an AX setup would also be a significant improvement for long trips.

jmargush, I did the same thing last year, interior tar mat, then 1/2 foam and then thin layer of perlon carpet. I do not have anything on the engine compartment wall. It nocked noise down by more then half. I do have Ben's sport muffler so that end is pretty loud. Mark

What do you suggest for the roof? Mine has nothing at the moment, didn't really consider the added sound deadening it would provide. Mine is pretty quiet but I could always use more..

Something like this. I don’t recall my OE headliner having edge binding but this should be close. On my 2nd car it is missing and yet to be replaced but I’ll use this or just cut some Perlon.

https://www.pelicanparts.com/More_Info/APBZ...eBoCu4MQAvD_BwE

Thanks guys great info!

My car (faux GT) has almost zero sound insulation, but I did rework my roof panel a while back to try and reduce heat transfer inside. I used a product called Dynaliner:

https://www.dynamat.com/products/dynaliner/

on the bare fiberglass, then purchased a precut headliner piece from 914Rubber:

https://914rubber.com/oem914563321113-1-700-charcoal-1-2975

to finish it out. Can't really comment on whether the heat insulation reduced the sound as the rest of the car is so loud at speed anyway; but the thermal reduction worked a treat ;-)

- Tony

Another question is there an opinion on whether loop carpet is more effective than perlon at reducing sound?

Loop all the way. Perlon is very thin and light.

Any opinion on just applying a sound deadening mat to the targa without carpet? Was thinking maybe a sheet of this stuff and calling it a day.

https://www.amazon.com/Siless-Sound-Deadeni.../dp/B07CG2YPRJ/

but that price I could just get carpet (if it were in stock).

@emerygt350

I’d avoid that product. It is just butyl as a mass damper. A constrained layer product like Dynamat is going to be more effective than just butyl.

I guess I’m wrong - looked again and it says it does have the aluminum constraint layer like Dynamat.

I'd do a search on other recent threads on sound deadening. As @Superhawk996 said earlier, different materials reduce different frequencies of sound. The firewall also has the engine noise to contend with which is why sound deadening in that area was designed as a sandwich of different materials to reduce sound levels.

Coming back from Octeeener fest, MY 75 914 did not have the fire wall blanket, on on return I purchased and installed a Synthetic blanket from Rix914 at the show..EZ install and made a noticeable difference in the reduction of engine noise in the cabin. Wish I had done this upgrade earlier . Rick is a great guy to work with too

Does that mount inside the cabin ? Are they available on-line ?
@rfinegan

It replaces the heavy tar/fiber mat inside the engine bay and is available online.

It's the same mat I went with and I really like it. I measured 1 dB sound reduction inside the cab compared with a less expensive sound/heat reduction mat. Unfortunately, I got too excited about installing the new mat and forgot to measure sound with no mat at all. It is significant though.

https://www.rix914parts.com/store/p29/914_F...uction_Mat.html

attaches with factor metal tabs and 3/ 4 push in fasteners from the engine compartment

Food for thought but don’t forget to focus on any window gaps as they contribute significantly to road noise and overall comfort.

Case in point I spent some time recently readjusting my door windows and seals. Couldn’t believe how much more relaxed I was driving the 1500 odd miles to Utah and back. My car is loud as hell so not implying it is quiet by todays standards, but my wife and I were never so relaxed after 5 hours in the car.

Years ago Stoodards used padding on the top above the roll bar to reduce sound.