Sound proofing experiment on the 370Z
 

So I figured since I didn't have much going on this long weekend I'd do a sound proofing project on the Z to see if it makes a difference.

My goal was to get the most gains without going crazy and tearing the entire interior out or using 30+lbs of sound insulation.
I went with my left over Dynamat and Frost king which you can source at the local home depot (2 of which didn't have it, FML) at 18.99 a roll.

A few comments to those that are thinking about frost king.

1. It isn't all that cheap. 18.99 gets you ~15 sq feet so about 1/2 the price of dynamat but given the way the material feels etc it may not be worth while.
2. It is very light 1/4 of the weight of dynamat, and I am not sure the sound insulation properties of this material by itself are good because they lack mass/density etc, but since I bought it I decided to use it.
3. It does have a slight smell on the glue layer, once you apply it it goes away (since it isn't exposed) but ... it could come back, I wouldn't use rolls of this **** in the car since it will likely smell. Dynamat is pretty much odor free.

I pulled apart the trunk of my Z which was surprisingly easy/quick. My first try took me about 30 min, if I was to pull it apart again, I can likely do it in 15 min or less. No broken clips or anything.

My strategy was to supplement factory sound deadening and add to flimsy/high noise areas. I put dynamat down as a baselayer, and put frost king on top since dynamat is the heavier more dense product.

I used about 10sq feet of dynamat ~4lbs. And I used about 10sq feet of Frost king ~1-2lbs. Total of 5lbs.

Overall the results were somewhat disappointing same as my golf where I did my entire trunk with dynamat. The car does seem a bit quieter but bad roads are still really shitty.

I took 3 separate measurements all at around 65-70mph on the same stretches of road.

Bad pavement
82-83 after 80-81
ok pavement
75-76 after 73-74
Good pavement
72-73 after 70-71

Overall I'd say it cut about 2-3 db out at best. Is it noticeable, yes... slightly. I was hoping for a reduction of 5-6db which would have been good. I do not think adding any more sound insulation makes any sense. I addressed all the key areas and anything incremental would be simply chasing a 10% improvement by adding 90% more weight.

I believe the next best thing to do would be to use thicker carpet type insulation as most OEMs. But that presents a lot of other challenges that I wasn't willing to tackle.

Here are some pics

Trunk plastics pulled (not the factory sound deadening was really thin and comparable to dynamat)


https://farm1.staticflickr.com/615/2...fd029cda_c.jpg

https://farm1.staticflickr.com/749/2...b860b628_c.jpg

https://farm6.staticflickr.com/5687/...63a484a5_k.jpg

Put more sound-deadening material on the shock towers, the reinforcement between them, and the wheel wells. Those are the noisiest areas.

To do a good job, you have to cover just about everything. The padding/carpet (plus the spare) damps a lot of the noise from the spare tire well, so skimp there if need be.

Some members have reported that doing the doors makes a big difference.

There are 3 layers of sound insulation on the wheel wells.

Factory
+Dynamat
+Frost king

I don't think adding more will do anything. The tower connecting the shock braces doesn't seem to be a source of noise it isn't close to the tires etc.

But thanks for the tips!

Covering the entire trunk is silly, that is not the right way of insulating, I did that on another car and it was quite pointless. I decided to go a more strategic route this time around.

What made the biggest difference for me was a layer of closed cell foam over the deadening material.

What is the brand of product that you used? and how thick is it?
Have you done any DB measurements ?
Frost king is CCF.

as Ark said you need to get the towers both sides and the centre piece as well. i'd also try and get into the wheel well as deep as you can get it. also the inner side of the trunk is nice and flat but has a big hollow noise.

i think you will get closer to the 5db reduction mark if you did a single layer over the entire thing and a double layer over the wheel wells but i can't back that up with tests.

the one thing to remember though is the dynamat/hushmat will not sound proof, it will only reduce the noise levels a little bit. my biggest notice is the road noise from the tires + the rock 'pings' from the underside. if you want to really reduce the noise you need to go the whole 9 yards.

The shock towers were solid metal and not paper thin 1/16" of an inch like the wheel wells and the bottom of the trunk. I got the wheel wells with two layers on the front and the back. On top of the factory material as well as some surrounding areas...

I'd like to see if someone actually got measurements of sound reductions. It is easy enough to go back and add more, but I don't want to waste time and add unnecessary weight. Covering the entire trunk etc is not wise just for the sake of covering it doesn't make sense.

to be fair you should have hit every piece of metal in your rear hatch so you didn't have to go back. all the metal parts will vibrate and send out the sound.

the dampening material adds mass to reduce vibrations and dampens the sound a bit. i think you would have hit your 5-db target if you did the entire hatch instead of portions but that's me speculating.

i'd suggest searching the audio section... tons of good material there to kill some time reading and learning :tup:

I did... I looked at at least 10 threads. Most don't have any measurements behind their claims. And from what I could tell most seem disappointed even after covering the entire trunk etc.

The proper way to apply material like dynamat isn't to cover every single space of metal but only a portion preferably in the middle of a panel i went a bit overboard since these cars don't even have wheel well liners?! WTF is up with that. Which explains the whole pebble issue.

Unless you're looking for mass damping through the sheer weight of the material. But that would require 2-3 layers of dynamat which would weigh 50lbs and is completely insane.

Anyways I was hoping to help others looking to quiet down the road noise and show them the approximate results with the route I decided to take.

As much as I searched I couldn't anyone that actually measured their before/after results.

5-6DB reduction is huge, and as I mentioned prior I haven't received that type of result on another car where I actually went full retard and covered the entire trunk since it seemed to be what most others were doing.

I received the same or better results on this car while only using 1/3 of the material!

Door panels, bottom of spare tire well, etc are good candidates for partial coverage; suspension-connected parts, not so much. Wheel wells definitely need complete and heavy/thick coverage.

If you don't want to add weight, add a bunch of home insulation, it absorbs sound surprisingly well. It's just super ghetto

I used this: Ensolite IUO Peel and Stick --- 1 yard (13.875 sq ft) - RAAMaudio Inc.

I put down a full layer of deadening material, and then a full layer of foam. It made a noticeable difference in road noise, but I don't have decibel measurements.

This is good info. That product looks similar in nature to Frost King but thicker it would be a good layer on top of Dynamat. Btw does it smell?

Makes sense. OEMs use similar products underneath carpets.

Not smell at all. And their deadener is fairly cheap, so you might as well make it a full layer while you're in there.

The main culprit for the road noise is the tires, though. You can't get around that with foam and deadener.

Mine are at roughly 80% tread. While tires do make a lot of noise this car has amazingly little noise insulation. The entire trunk only has a few strips of 1/16" sound insulation. Usually there would be some kind of carpet or a wheel liner etc.

My original idea was to pull down the wheel liners and put dynamat there... then I ducked into the wheel wells and was shocked to find nothing there.

I have never had a car without wheel-well liners.

My car isn't very loud over good pavement but it is really bad over coarse pavement. I was hoping to cut that down a bit.

Do you have any exhaust work?

100% stock.

i agree with that statement about 2-3 full layers being insane but i did double up on the wheel well since there was no insulation as you have pointed out.

one of the things to remember is this is a pure-bred sports car. it's not a luxury sports coupe or anything close to a 'luxury' branded car so you won't be getting the same conveniences that come with the luxury badge.

i tried just the wheel wells and the spare wheel section, went back and did the entire trunk and noticed an improvement. also going from the stock tires to re-11's made a big improvement in road noise.

the road noise is fine minus hearining the pebble pings and long drives (more than a few hours). I did a few 4 hour drives before and after the install and it definitely helped relieve the road noise stress.

Some truth to this but I have the same options as a Infiniti g37. Nav, leather, Bose with sub, heated seats etc. Saving 10-15 lbs in a non light 3350lb coupe seems asinine considering how much it can ruin the experience. Even with my 4-5lb hackjob the car is far more enjoyable on longer freeway runs.

Sent from my XT1060 using Tapatalk

The Infiniti G weighs like 400lbs more, though. And that's all sound proofing.

And the Z is a light coupe. Compared to most cars in its class it weighs a couple hundred pounds less.

It is over a foot longer and has a back seat... A Porsche boxster S is 350lb lighter. Anyways ...

There aren't many 2 seater sports cars around the z size other than the corvette which is roughly the same weight while packing 100+ hp

But to be fair, our floorboards aren't made of balsa wood.

i swear they are made of some sort of engineered metal to transfer the sound from the tires into your ear balls

Put some dynamat in the wheel wells with FK on top and some frost king on the wheel liners. Really shitty pics... sorry about that. Will report DB findings later.


https://farm1.staticflickr.com/564/2...52d3ffb5_c.jpg


https://farm1.staticflickr.com/668/2...78668a89_c.jpg

I've considered using some of the exterior spray on deadening in the rear wheel wells to really cut down the noise. That may be the ticket.

Final update.

Approximately 3-4 DB decrease from stock. The car is now decent in terms of road noise and you can easily hold a conversation with a passenger without feeling like you're in a club.

Total weight add was around 4-5lbs. Totally WORTH it mod in my mind.

No this car is not a VAULT as some like to describe these experiences. But it is certainly more livable and no longer a nuisance.

FrostKing?
 

BlueZ, What is the name of that CCF FrostKing? I haven't been able to find it.
Thanks
I like the sound deadening spray idea. If we could just get a even application.

I would recommend going the same route as me and adding Dynamat around the wheel wheels since it adds an initial layer of mass damping. Even with those two layers in place there is still room for improvement in that area. There is a TON of noise coming from there from the factory.

Frost king Fv516

Shop Frost King 15-ft Roll Insulation at Lowes.com

wow you went and did it to the plastic liners! i just plopped it onto the inside shell.

glad you got the change you were looking for without breaking bank!

Sound Control Insulation - Sound Damping Coating | LizardSkin

This is what I was thinking about.

Ton of Noise!
 

That's for sure. I just returned from a 6 week, 6095 miles road trip.
PS: America is a beautiful place.
Regards

I would think that would be good. Or something like a trunk liner in trucks for the inside wheel wells.

Yea after doing the rears first I started to hear a lot more noise from the front. I figured since I was at it already might as well do the wheel liners.

Most OEMs use sound insulation on the wheel liners themselves.

Without going the extra mile and getting the car into a sound chamber, I figured I'd mimic what luxury oriented OEMs spent millions on in order to prevent road noise, the general principles are the same for all cars.

My Mazdaspeed had stuff on the liners. I feel like I mostly hear sound from the back, but I can see how adding on both ends would help. When my house is done and I have my own garage, I'm probably going to start adding this to the hatch area first and work forward. First order of business is finding the F*CKING heatshield that's rattling right now. Makes me feel like a Civic...

Honestly adding sound insulation in the back is super easy in this car. The plastics come out in 8-10 min and it is super easy... the easiest car to pull apart that I have worked on so far. So straight forward and easy.

I did this back when I first got my car. Lined the hatch and doors with Raam Mat then a layer of their Ensolite foam padding. While the car is still loud (mainly because of my tires), it made a huge difference by eliminating the 'tinny' sound/feel when you went over pebbles. The car sounds more solid and that was what I was after.

have you considered lining the door's aswell? i did my doors + hatch and rear wheel weels.

didn't bother with the floor under the seats or roof. i found i could hear the exhaust and engine hum a lot more clearly after i did those 2 sections.... but that's based on perception

I'm OK with the car now. I'd say 60% of the noise comes from the rear wheels and 30% from the fronts... 10% is other areas that are much harder to address

Sent from my XT1060 using Tapatalk