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2022 Outback Touring XT. Also 1995 BMW 525i with 240,000 miles
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Discussion Starter · #1 ·
I decided to sound proof the cargo area of my 2017 Outback Limited 2.5. I reached this decision after I rode in the back and road noise was excessive on old rough blacktop and concrete roads. My wife, who wears two hearing aids, noticed it as well. It seemed to be coming mostly from the rear wheel well area, particularly the passenger side.

After lots of reading, watching redundant YouTube videos and checking prices of material and the cost of having it done professionally, I got one estimate of $500 just to just Hushmat Ultra the wheel well area. They would not quote doing anything else till they took it apart. Therefore, I decided to do it myself. It was not difficult, just tedious

The goal was to sound insulate the cargo floor area from the back of the backseat and the wheel wells. At the present time, I excluded the tire well which is about 13 square feet. I plan to do it later. I wanted to stop both panel vibration and sound transmission. Research indicated a composite of materials works well. Usually, that entails a layer of Dynamat or Hushmat (or similar) then a layer of Dynapad or Silencer Megabond foam This second layer, rather expensive is usually closed or open cell foam (available in different thickness) and another layer of Dynamat or Hushmat like material. Then just replace panels.

The first step was to remove panels. I did not remove rear seat back as it seems unnecessary. I did remove everything else including the rear seat bottom. I did not remove cables, motors or electronics. I just worked around them which was a little tedious. Look at the Outback shop manual or search online on how to remove all the panels. There are a few plastic Christmas tree like plastic screws, metal screws/bolts and side seat bolsters to remove.

Due to cost, I ended up making my own composite of three layers. Project sure took a lot of time. I spent about 13 hour’s total. I used about 23 square feet of Hushmat Ultra black sets 10300 and10150 to cover the entire floor area and wheel wells, plus some fender side areas on the driver’s side. This stuff has very strong adhesive. I DID NOT remove the speaker on the rear passenger side as it was fairly boxed in. I bought my Hushmat Ultra on Amazon Prime for about $120. Also, make sure you DO NOT cover up any of the holes you need to reinstall panels. Use a roller for best adhesion. I used my wife’s wallpaper roller.

Next step was to cover ONLY the wheel wells with 3/16 black closed cell foam purchased on e-bay for about $20 including shipping. It did not have an adhesive. I used about 10-15 square feet of foam. I cut pieces to fit and glued them over the Hushmat with either 3M contact adhesive or Permatex as I had both. I tried to have minimal gaps with very little overlap. You could use thicker foam but is harder to handle and may cause clearance problems. I had no clearance problems. I used some Hushmat quiet tape 30300, about $20 at Amazon Prime to fill in odd spots and to hold some edges down. It comes in 1”x20’ roll of what appears to be thin strong foam with super strong adhesive.

The final step in my project would be to cover (for the third layer) the foam areas with Dynamat of Hushmat. Instead, I went cheap. The YouTube videos talked about a cheap way to sound proof your car. Some of the posts on this forum have mentioned it. I used Peel and Seal aluminum roofing material instead of the expensive stuff. It is a 6”x 25’ feet roll of material with a rubberized asphalt adhesive. I purchased it from Lowes for about $14. It does look similar to Hushmat, just thinner with a different backing and adhesive. I would not use it for primary sound proofing. I just covered the wheel well area with Peel and Seal making sure I covered all seams or spaces in the foam. In my opinion the third layer sort of decoupled or separated the two layers of metal based material. Hopefully creating a dead air space will block some sound. Now I have a 3 layer composite over the wheel wells and one layer of Hushmat over the entire floor area, but not the tire storage area. I did cut a piece of closed cell foam to fit under the Outback cargo mat. All the above should function as a package to reduce road noise.

Did it help with road noise? Yes, it did. I no longer hear the rear tires hit bumps and overall road noise is considerably lower. The sound level is still about 64 dba at 70 mph in the front seat, but the sound is different. I think I hear the wind noise a bit more. Glad it did it. Took a lot of time. However, I am retired and have the time to devote to all sorts of interesting projects. :)
 

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2022 Outback Touring XT. Also 1995 BMW 525i with 240,000 miles
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Discussion Starter · #2 ·
I did not include a picture but the wheel well area that is beside the rear seat, covered by the seat bolsters, also got the 3 levels of insulation. before I took of the side cargo area covers, I did not know they had a layer of sound insulation. The 2018 OB is supposed to have improved sound insulation around the rear wheels. I wonder if it is simply better panel insulation.
 

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2022 Outback Touring XT. Also 1995 BMW 525i with 240,000 miles
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Discussion Starter · #3 ·
Anyone have other ideas what to soundproof next on the 2017 Outback. I am thinking of the doors, under the rear seat and the spare tire area. I do not, at this time, intend to remove the front seats and carpet. Seats are heavy. :)
 

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Brucey
'17 3.6
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12,372 Posts
Did you put in any Mass loaded vinyl?

It's my understanding the dynamat just adds mass to reduce the frequency and the foam is for insulation from that. The MLV will physically block noise.

It's heavy, about a pound per square foot.
 

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Discussion Starter · #5 ·
Did you put in any Mass loaded vinyl?

It's my understanding the dynamat just adds mass to reduce the frequency and the foam is for insulation from that. The MLV will physically block noise.

It's heavy, about a pound per square foot.
No. I used first Hushmat, similar to dynamat, then 3/16" closed cell foam and then a layer of Peel and Seal. This created a "package" that is blocking sound. I only did the 3 layering over the wheel wells.

It seemed to mimic the more expensive Silencer Megabond foam that Husmat sells. I could be wrong. However, it seems to be helpful.
 

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Brucey
'17 3.6
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Hmmm. I plan on doing some sound deadening on mine at some point. Mostly want a more isolated ride when driving long distances with the BFG KO2 tires on as well as better sound quality through the factory stereo.

I could do it in sections like one door at a time on my lunch break without much down time.

If you're saying it has no measurable effect doing it on the wheel wells I might skip it.
 

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I looked at the 18's inner fender wells and they are still plastic compared to the new Impreza's cloth /felt ones. I have a 16 OB and I think it's quiet. If I replace the tires even more so I'm a little confused on the effort? Maybe your car lacked something from the factory that would make it quieter? Are all the bogy plugs in?
 

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Discussion Starter · #8 ·
Hmmm. I plan on doing some sound deadening on mine at some point. Mostly want a more isolated ride when driving long distances with the BFG KO2 tires on as well as better sound quality through the factory stereo.

I could do it in sections like one door at a time on my lunch break without much down time.

If you're saying it has no measurable effect doing it on the wheel wells I might skip it.
IMO, covering the wheel well areas is the prime reason the sound is reduced.To my ears, the background noise level is significantly lower over rough roads. Over smooth roads, it is also lower as tire noise is reduced.

I did not have a dba noise level reading before and after from the back seat. As I previously said, I could hear the wind noise, 70 mph, a bit more after insulation but it was the same Dba level as before. However, the sound is much different. Hard to explain but I think background noise is reduced.
 
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Discussion Starter · #9 ·
I looked at the 18's inner fender wells and they are still plastic compared to the new Impreza's cloth /felt ones. I have a 16 OB and I think it's quiet. If I replace the tires even more so I'm a little confused on the effort? Maybe your car lacked something from the factory that would make it quieter? Are all the bogy plugs in?
Ride in the back seat on rough roads and you might hear the noise. Yes, the bogy plugs are in.

I noted the same inner fender liners on a 2018 as my 2017. Not sure what they did to reduce sound.

The effort was an experiment. I hoped it would help and it did. Just a little money and time. :)
 

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2016 Outback 3.6 Ltd Red/ES,20 mm RSB
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Anyone have other ideas what to soundproof next on the 2017 Outback. I am thinking of the doors, under the rear seat and the spare tire area. I do not, at this time, intend to remove the front seats and carpet. Seats are heavy. :)

Next step should be door panels.They stop a lot of noise but not all. Try to drive without one for a day and you see what I mean.
Interesting site about NVH https://www.sounddeadenershowdown.com/
 

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Discussion Starter · #11 ·

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Discussion Starter · #12 ·
Doing more research on how to approach sound proofing other areas of my OB. May use additional techniques and materials. I also need to understand how door panels and kick panels can easily be removed on the 2017 OB . Should be easy since I have panel removal tools and have done it on other cars. :)
 

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Discussion Starter · #14 ·

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I put a bunch of dynamat in my 14 crosstrek and it made a difference. I upgraded the entire stereo system at the same time. I've noticed in the 2 days I've owned my 16 OB limited that the door skins are verrrrrry thin. I see and hear the sheet metal wobble when the door is closed. Interior road noise is already better than the XV, however. I think I will add some material to the doors to tighten them up a bit.

One thing to remember for anyone considering adding any material: the dynamat is not sound deadener, it is a vibration reducer. The foam/stuffing type material commonly jammed inside a door is the actual sound deadener. That can be a misconception with some folks, when combined with each other is when you achieve the best result.
 

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Discussion Starter · #16 ·
I put a bunch of dynamat in my 14 crosstrek and it made a difference. I upgraded the entire stereo system at the same time. I've noticed in the 2 days I've owned my 16 OB limited that the door skins are verrrrrry thin. I see and hear the sheet metal wobble when the door is closed. Interior road noise is already better than the XV, however. I think I will add some material to the doors to tighten them up a bit.

One thing to remember for anyone considering adding any material: the dynamat is not sound deadener, it is a vibration reducer. The foam/stuffing type material commonly jammed inside a door is the actual sound deadener. That can be a misconception with some folks, when combined with each other is when you achieve the best result.
FYI, I just ordered a sample product kit from Vehicle Sound Deadening Materials for Noise Reduction, and Thermal Insulation. Call 800 679-8511. | Second Skin Audio, Made in the USA..
The cost was $10 including shipping. It will help me decide on what products to use for my next steps. I think I will finish the rear seat area next. A lot of opportunity for noise there and plenty of openings such as seat belts, latch connections, and gaps around the edge of seats for noise to seep out. MLV might be used there.
 
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Discussion Starter · #17 ·
I received the sample kit as I stated above. I think I am going to lay down Hush mat under the rear seat where I can, then make a 1/8" MLV mat with 1/8 " decoupler foam to cover the entire area under the seat then seal the edges with some sort of tape. I may see what can be done on the rear floor boards without taking the front seats out. I may also put hush mat in the deck lid. However, I hear that is not a significant noise issue.

As for wind noise, one sound material supplier informed that a lot of wind noise is actually transmitted through the doors. Not sure about that one. :)
 

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Discussion Starter · #18 ·
I finished sound proofing under my rear seat and rear seat riser today. I went all out. Covered every thing in black Hushmat. Tied that into the Husnmat I previously placed in the cargo area. I have the entire cargo area surface up to the rear floor board covered in Hushmat.

Then I covered the area under the rear seat and seat riser with 3/16 closed cell foam and 1/8 Mass loaded vinyl (MLV). The foam and MLV are not attached to the Hushmat. They are "decoupled". This is supposed to block sound. I finished with lining my spare tire well with the remaining black Hushmat. This entire job took me about 6 hours to complete. I am slow :).

I guess the next steps would be the floor board and doors. Doubt if the floor will be done even though the carpet is thin with about 3/8" of fairly dense white foam on the underside. Not sure I want to take all that apart. Doors might be done.

I have not driven it yet to see if there is a road noise reduction. It has been raining and I want to compare on dry roads. I suspect a little improvement. Nothing terribly big. My previous efforts made a big difference.
 
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I finished sound proofing under my rear seat and rear seat riser today. I went all out. Covered every thing in black Hushmat. Tied that into the Husnmat I previously placed in the cargo area. I have the entire cargo area surface up to the rear floor board covered in Hushmat.

Then I covered the area under the rear seat and seat riser with 3/16 closed cell foam and 1/8 Mass loaded vinyl (MLV). The foam and MLV are not attached to the Hushmat. They are "decoupled". This is supposed to block sound. I finished with lining my spare tire well with the remaining black Hushmat. This took me about 6 hours to complete. I am slow :).

I guess the next steps would be the floor board and doors. Doubt if the floor will be done even though the carpet is thin with about 3/8" of fairly dense white foam on the underside. Not sure I want to take all that apart. Doors might be done.

I have not driven it yet to see if there is a road noise reduction. It has been raining and I want to compare on dry roads. I suspect a little improvement. Nothing terribly big. My previous efforts made a big difference.
Look forward to to your report. I just picked up a 2018 Outback Limited and its quieter than my 2015 for sure. But I do hear more road noise from the rear since the front seems inherently quieter than my 2015. FWIW, may 2015 had Hushmat in the front doors and under carpet from front to the base of the rear seat. Did not do the rear doors in the '15. all that said, I'm not sure how much difference all that made in the '15.

And now the 2018, the new OB seems quieter than my '15 that had some hushmat upfront.
 

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Discussion Starter · #20 ·
Look forward to to your report. I just picked up a 2018 Outback Limited and its quieter than my 2015 for sure. But I do hear more road noise from the rear since the front seems inherently quieter than my 2015. FWIW, may 2015 had Hushmat in the front doors and under carpet from front to the base of the rear seat. Did not do the rear doors in the '15. all that said, I'm not sure how much difference all that made in the '15.

And now the 2018, the new OB seems quieter than my '15 that had some hushmat upfront.
Short report. I will add more as I gain experience. Took a short trip to pick up pizza last evening and noticed two things. The car felt very solid and I could not hear the rear wheels going over small bumps. Remember this is the combination all I did previously and the new work. If I was doing there cargo area again, I might use MLV over the wheel wells.

As a side, I am interested in materials and techniques you used for the doors and carpet. I am really considering doing that work at some point. Bit concerned about taking the seats out with the airbags and all. :)
 
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