Sound absorber replacement
08-23-2018, 12:08 PM
#16
Rennlist Member
I ended up using the rennline aluminum cup floor boards. wood would be lighter probably. you can use small squares, that can work, on my roof, we put several patches. it was interesting, prior it sounded like a tin can, now it's dead/silent.
basically you just want to deaden the resonance.
On the removal of the old materials. It's a HUGE job. Don't under estimate the PITA it is. My shop did it, and it took a few days. One of their Jr. guys did it, well he's not so Jr. now he's done a lot of the mechanical on the car (hes really good) so this helped him bond with it :-) They used a citrus solution with plastic razors and scrapers.
heavy chemicals better, but in an active shop with lots of sparks and heat...
basically you just want to deaden the resonance.
On the removal of the old materials. It's a HUGE job. Don't under estimate the PITA it is. My shop did it, and it took a few days. One of their Jr. guys did it, well he's not so Jr. now he's done a lot of the mechanical on the car (hes really good) so this helped him bond with it :-) They used a citrus solution with plastic razors and scrapers.
heavy chemicals better, but in an active shop with lots of sparks and heat...
08-23-2018, 02:49 PM
#17
08-23-2018, 05:58 PM
#18
Racer
I think some of you are over thinking it here. Sound deadening is pretty simple. There are a lot of ways to achieve various levels of deadening.
The cost is weight.
For me, I wanted to get rid of the 'tinny' noise of the car with the interior completely stripped. Also the whine from the trans-axle and front diff were very loud.
Attachment 1349564
My solution was to put a double layer of Dynamat in the back firewall and rear seat area as well as on the front firewall. Same thing for the entire length of the drive shaft tunnel.
A single layer of Dynamat on the floor and along the sides. Then I covered everything with an acoustic foam padding like Dynaliner for under the carpet. Then the carpet itself. Turned out great and eliminated the noises I was targeting.
Wow, just looked at my pictures again and these are friggen bad pictures. Honestly, the work looks way better than these let on! LOL.
The cost is weight.
For me, I wanted to get rid of the 'tinny' noise of the car with the interior completely stripped. Also the whine from the trans-axle and front diff were very loud.
Attachment 1349564
My solution was to put a double layer of Dynamat in the back firewall and rear seat area as well as on the front firewall. Same thing for the entire length of the drive shaft tunnel.
A single layer of Dynamat on the floor and along the sides. Then I covered everything with an acoustic foam padding like Dynaliner for under the carpet. Then the carpet itself. Turned out great and eliminated the noises I was targeting.
Wow, just looked at my pictures again and these are friggen bad pictures. Honestly, the work looks way better than these let on! LOL.
Last edited by klokwerk; 08-23-2018 at 06:18 PM. Reason: pictures are ugly
08-23-2018, 09:32 PM
#19
Rennlist Member
I think some of you are over thinking it here. Sound deadening is pretty simple. There are a lot of ways to achieve various levels of deadening.
The cost is weight.
For me, I wanted to get rid of the 'tinny' noise of the car with the interior completely stripped. Also the whine from the trans-axle and front diff were very loud.
My solution was to put a double layer of Dynamat in the back firewall and rear seat area as well as on the front firewall. Same thing for the entire length of the drive shaft tunnel.
A single layer of Dynamat on the floor and along the sides. Then I covered everything with an acoustic foam padding like Dynaliner for under the carpet. Then the carpet itself. Turned out great and eliminated the noises I was targeting.
Wow, just looked at my pictures again and these are friggen bad pictures. Honestly, the work looks way better than these let on! LOL.
The cost is weight.
For me, I wanted to get rid of the 'tinny' noise of the car with the interior completely stripped. Also the whine from the trans-axle and front diff were very loud.
My solution was to put a double layer of Dynamat in the back firewall and rear seat area as well as on the front firewall. Same thing for the entire length of the drive shaft tunnel.
A single layer of Dynamat on the floor and along the sides. Then I covered everything with an acoustic foam padding like Dynaliner for under the carpet. Then the carpet itself. Turned out great and eliminated the noises I was targeting.
Wow, just looked at my pictures again and these are friggen bad pictures. Honestly, the work looks way better than these let on! LOL.
08-23-2018, 09:33 PM
#20
Rennlist Member
Join Date: Jun 2014
Location: Tennessee
Posts: 982
Likes: 0
Received 0 Likes
on
0 Posts
I read a lot about this a year ago. Goals are to stop vibration as much as possible ( things rubbing together). And then blocking sound. Unfortunately what accomplishs this is mass( weight).
A lot of sound comes from the windows. I put dynaliner down then thick felt and then mass loaded vinyl.( google this to find articles) all in all I couldn’t tell much difference and pulled it out because I didn’t want the extra 20 lbs in there.
A lot of sound comes from the windows. I put dynaliner down then thick felt and then mass loaded vinyl.( google this to find articles) all in all I couldn’t tell much difference and pulled it out because I didn’t want the extra 20 lbs in there.
08-24-2018, 03:31 AM
#21
Rennlist Member
Sound deadening requires absorption of vibration- resonance frequency - and sound absorption - which is handled well by the oem foam and the tar like material...
In the stereo world - this is done effectively through constrained layer dampening - so the use of materials that resonate at different frequencies so the initial vibrations are changed and blocked and deadened as they travel through the material. So- for a wall, as example, you can use layers of different types of wood, with sheets of aluminum and gypsum board mixed in, and then foam on the outside, that kill all the noise. If you go too far, you can make a chamber that feels very strange to be in, because your brain doesn't like "zero" sound.
Macintosh has an anechoic chamber in their lab in Binghamton, Ny where they test speakers that's very disorienting.
In a car- it's very complex, because we have weight and space constraints. And so it becomes about compromise. How much noise, and what type of noise, etc. Aka, drone sucks.
And it also sucks to not be able to talk on the phone because the microphone is picking up all the noise and cutting everything off...lol.
I've been thinking about this a lot lately, as we will be doing a weight saving program on the Alabama car once it gets back from getting its new motor, and it's going to be loud. But we want to remove the heavy oem sound deadening and attempt to lessen the noise where it's necessary.
So the questions become- where is the source...and then deaden first, vibration from those areas, and then absorb the sound waves traveling through the cabin.
Should be fun- so i hope some sound experts will chime in here. We have to have some audiophiles that have worked on cutting noise in a 911 around.
Fwiw- the one thing i haven't worked out yet- is the main source of loud cabin noise and drone- which is the vibration and sound that travels up the c pillars to the roof. The roof on a coupe acts as a speaker and clobbers your ears. Targa and cab don't have this problem and can be much more pleasant to drive in as a result.
VW bugs had a molded foam piece that got stuffed up into the c pillar from the bottom for this reason.
Downside to our problem. Is that there is no real sound deadening solution that isn't heavy. So my question and what i will attempt to explore is how to take out weight and use a good set of contemporary materials in just the right places, to take the sound down, but still lose weight.
Has to be possible.
In the stereo world - this is done effectively through constrained layer dampening - so the use of materials that resonate at different frequencies so the initial vibrations are changed and blocked and deadened as they travel through the material. So- for a wall, as example, you can use layers of different types of wood, with sheets of aluminum and gypsum board mixed in, and then foam on the outside, that kill all the noise. If you go too far, you can make a chamber that feels very strange to be in, because your brain doesn't like "zero" sound.
Macintosh has an anechoic chamber in their lab in Binghamton, Ny where they test speakers that's very disorienting.
In a car- it's very complex, because we have weight and space constraints. And so it becomes about compromise. How much noise, and what type of noise, etc. Aka, drone sucks.
And it also sucks to not be able to talk on the phone because the microphone is picking up all the noise and cutting everything off...lol.
I've been thinking about this a lot lately, as we will be doing a weight saving program on the Alabama car once it gets back from getting its new motor, and it's going to be loud. But we want to remove the heavy oem sound deadening and attempt to lessen the noise where it's necessary.
So the questions become- where is the source...and then deaden first, vibration from those areas, and then absorb the sound waves traveling through the cabin.
Should be fun- so i hope some sound experts will chime in here. We have to have some audiophiles that have worked on cutting noise in a 911 around.
Fwiw- the one thing i haven't worked out yet- is the main source of loud cabin noise and drone- which is the vibration and sound that travels up the c pillars to the roof. The roof on a coupe acts as a speaker and clobbers your ears. Targa and cab don't have this problem and can be much more pleasant to drive in as a result.
VW bugs had a molded foam piece that got stuffed up into the c pillar from the bottom for this reason.
Downside to our problem. Is that there is no real sound deadening solution that isn't heavy. So my question and what i will attempt to explore is how to take out weight and use a good set of contemporary materials in just the right places, to take the sound down, but still lose weight.
Has to be possible.
In practical terms dynamats purpose is to reduce vibrations. You don't need much.
You then need a sound barrier. That is what the crumbling vinyl black stuff is. It basically blocks the sound. It's heavy but works great. MLV is the product and you can get rolls of it.
Then you put closed cell foam between the barrier and the sound source to absorb. Closed cell is important so it doesn't absorb moisture.
This site is really good about explaining above more.
www.sounddeadenershowdown.com/products
There is a reason why Porsche put the crumbling vinyl and foam on the floor pan as there is lots of road noise transmitted there. The other noise and heat source is the engine. So basically blocking the sound behind you will also help cut noise.
08-24-2018, 09:16 AM
#22
Rennlist Member
Thread Starter
So to replace the current crumbling OEM sound absorber, I cut a pc of Dynamat Xtreme; then some closed cell foam (source?) over that ?
Has anyone successfully shaped the foam so the carpet lays flat ?
Has anyone successfully shaped the foam so the carpet lays flat ?
08-24-2018, 09:53 AM
#23
Rennlist Member
...Fwiw- the one thing i haven't worked out yet- is the main source of loud cabin noise and drone- which is the vibration and sound that travels up the c pillars to the roof. The roof on a coupe acts as a speaker and clobbers your ears. Targa and cab don't have this problem and can be much more pleasant to drive in as a result...
To test this, the next time you are driving, push on the sunroof panel. The sound level change is pretty dramatic. That surprised me.
08-24-2018, 11:22 AM
#24
Rennlist Member
Forgot. Your door also big source of sound. I drove around for a few weeks with my panels as I was fixing them. Incredible how much road noise leaked in. I noticed the factory out a tar layer similar to dynamat at the bottom of the door shell to absorb the ringing when you close the door. There is a thin foam layer between the door card and door as the decoupler. And the vinyl/wood of the door card acts as the barrier.
All of the interior pieces act as sound absorbers/blockers.
In re to the floor, on my other car I basically layered the closed cell foam in the valleys so it was flat with the ridges. Not sure what condition your factory foam is but it is nice because it is is molded to the pan. Maybe you can cut it and reuse if it's still intact. Alternate source of the closed cell stuff are cheap yoga mats from walmart. The foam doesn't have to be contiguous. The vinyl barrier does to be effective. People use tape on the seams.
All of the interior pieces act as sound absorbers/blockers.
In re to the floor, on my other car I basically layered the closed cell foam in the valleys so it was flat with the ridges. Not sure what condition your factory foam is but it is nice because it is is molded to the pan. Maybe you can cut it and reuse if it's still intact. Alternate source of the closed cell stuff are cheap yoga mats from walmart. The foam doesn't have to be contiguous. The vinyl barrier does to be effective. People use tape on the seams.