I’ve been reporting on the sound insulation project since early-December just ahead of making a 1,600-mile round-trip to visit my folks in Pennsylvania. We were experiencing what sounded like an out of balance tire/wheel or perhaps a rear differential issue that really highlighted just how much sound was being transmitted into the truck cab by the composite cargo bed, basically a monolithic box molded out of a single sheet of filament fiber material sandwiched between two layers of plastic resin.
My reasons for doing this were two-fold: it was something all but the most luxurious of trucks need as they tend to be noisy — hey, they’re trucks — and it was something I regretted not doing in our 2006 Toyota Tundra. Mind you, throughout the life of the Tundra our “other car” was Debbie’s S2000 which was anything but quiet. So, it wasn’t until we replaced the S2000 with Debbie’s 2017 Honda Accord Sport LE that we suddenly found ourselves in a relatively quiet vehicle for the first time since replacing our 2002 Suburban Z71 with the 2006 Toyota Tundra. OMG, what a relaxing experience that was on a long trip! And since we’ll be using the Tacoma for long trips…. There you go!
In terms of how to go about planning and installing the sound insulation, I’d done a good deal of research on the subject and found that a lot of folks spend a lot of time and money doing the wrong thing based on “what they saw on TV car modification shows” or saw other people doing who probably watched those TV shows. And that was to cover the entire interior with this rubbery, stick-on vibration dampening product called Dynamat. Sadly, Dynamat doesn’t really do much to stop airborne sound, just the sounds that resonate on solid surfaces, like door panels, plastic trim pieces, etc. You can certainly reduce noise and made a solid-sounding vehicle by applying lots of Dynamat, but it has it limits. In fact, the sound control experts suggest treating only 25% of the targeted areas will achieve 100% of the desired result. Therefore, my guess is, these “Reality Shows” and other shows like them are given all kinds of free material by companies like Dynamat who hope to yield future business from the product placement and they really don’t care about mis-using their own materials. But, to their credit, their materials are a lot easier to apply and do reduce noise.
For my application, I followed the process outlined by a business that specializes in sound control, even so far as going to provide a by-vehicle shopping and application list of materials to help with making your material purchases. The approach they recommended was a multi-layered / multi-material application that included:
- Applying 80 mil thick Noico Constrained Layer Damper (CLD) tiles to the inner side of the door’s sheet metal skins for vibration dampening. (Essentially Dynamat)
- Applying extruded butyl rubber rope into gaps along the internal door support structure for vibration dampening.
- Fabricating and installing a full coverage sound barrier made by bonding 1/8″ thick Closed Cell Foam (CCF) / Neoprene to 1/8″ thick Mass Loaded Vinyl to keep noise from moving through the doors in either direction, i.e., it keeps road, tire and other external noises from getting into the truck while also enhancing the quality of conversation and music within the truck.
I’d ordered most of the sound insulating materials before we headed to Pennsylvania, assuming they would arrive shortly after we returned home and then I’d install it while I had the seats out of the Tacoma for recovering with the LeatherSeats.com seat covers which were also due to arrive the day we returned home. Well, I made two bad assumptions: shipping time would be longer than it was and doing the sound insulation would be a much more involved process that I would have to do after the seat cover upgrade, lest the truck sit torn apart in the garage for a week.
Anyway, upon our arrival at home a day later than originally planned we had a garage full of large boxes that had been delivered over the past few days, the majority of which had arrived earlier in the day after being on a delivery hold. There was one very large box with the leather seat covers, four boxes with sound insulation material of various sizes, a tote bag and then several smaller items such as a wireless charging adapter for my phone, center console organizers, interior trim panel removal tools and one of two tools I’d need to install the leather seat covers.
Getting a Baseline on Sound Levels in the Cab:
Being overly curious about making sure the things I modify achieve the desired effect to have warranted the effort and expense of the change, I decided to quantify just how much noise we had in the cab of the truck before I installed the sound insulation so I could then check it again after the installation.
To do that required a sound level meter. I purchased a very inexpensive hand-held device that seemed to do exactly what you’d expect it to do: measure sound levels. In my few trials around the house at the end of December the results were on par with what sound meters costing 10x as much are able to measure so it would be more than adequate for my needs.
The results from the first two test readings were interesting:
- Right Front / Passenger Seat: It ranged from the mid-40’s at idle to a high of 70.5 dBA, hovering mostly in the low- to mid-60’s at just about any speed above 40 mph.
- Right Rear Seat: It ranged from the mid-30’s at idle to a high of 80.5 dBA, a noticeably higher amount of noise which is consistent with what Debbie observed when she rode in that seat when we took my mother out to dinner on 17 December. I’m expecting a big drop in the rear seat noise once the back wall, riser and floor are sound insulated as it’s mostly road/tire noise and other noise coming from the rear axle.
- Left Rear Seat: Similar to the right, the high was only 76.4 dBA, which could be because the fuel tank sits on the left side of the truck and likely attenuates some of the rear road/tire/axle noise.
During a third test reading I saw nearly identical sound levels under the same conditions. So, regardless of how accurate the inexpensive sound level meter I purchased may be, it’s certainly consistent. So, I should be able to quantify any changed before and after the sound insulation is installed. In case you were curious how I was able to get my readings where it mattered and in a consistent manner, you can see my technique at right.
Installation Day 1: Doors
It was around 9:00am on a rainy Saturday morning in January when I moved the Harley out of the way in the first garage bay, fired up the Kerosene heater to bring the space up to a sound-insulating material-friendly 70°F, and began to get all of my tools and materials out and ready for pulling apart the four doors and installing the sound control materials.
Again, to recap, the approach I was using involved:
1. Applying self-adhering, 80 mil thick 6″ x 10″ pieces of vibration dampening material to flat metal and large plastic surfaces to achieve about 25% coverage.
2. Applying extruded butyl rubber rope into gaps along the internal door support structure for vibration dampening.
3. Fabricating and installing a full coverage sound barrier made by bonding a very heavy sheet of mass loaded vinyl to a piece of neoprene that acts as a vibration dampener between the mass loaded vinyl and sheet metal.
I don’t know that there are any shortcuts to this process other than being able to create a template for the rear door barrier using the very pliable neoprene and then using that to layout the 2nd rear door’s Neoprene and both of the MLV panels. Same thing up front; you create your template for one of the doors and then layout the other three sheets of material. Other than that, it’s all labor-intensive, custom fit and finish work.
Removing the door panels on the Tacoma is not hard: there are two screws a couple wire connectors and two control cables and a variety of plastic fastener clips. Having a set of plastic trim removal tools is essential; under no circumstances attempt to use metal tipped tools on soft plastics: once scratched, plastic is scratched. Once you’ve removed a couple of small trim pieces, cover plates for screws, removed those screws, popped-off a window & lock control panel and disconnected the wiring socket you literally “jerk” the interior trim panel off the door. Once separated from the door, there are two cables that control the door handle and locks that need to be disconnected and then the panel is free. This is the same for all four doors.
With the door panels removed you’re next faced with a plastic vapor barrier attached to the door with a strip of butyl rubber and this is where cold weather is your friend. With enough of the vapor barrier pulled back, you can then pull out some foam plugs in the larger door panes that finally gives you access to the inner door space. So, what you start with are empty door cavities / echo-chambers with maybe a single token piece of vibration dampening material.
The photo at right shows the rear door after applying the Noico / CLD Tiles.The door panels present some challenges since much of the material you’re installing has to be put on through access holes in the door so a lot of the work is done by feel. In addition to putting 6″ x 10″ tiles of Noico material on the inside of the external door skins to achieve ~25% coverage. Butyl rope was used along the gap between the side impact post and the outer door skin to address resonance along the post. The rest of the treatment applications were to wide-open, mostly flat surfaces such as the face of the inner door panels near the speakers and door handles. The nice thing about the Noico / CLD material is that you’re immediately able to appreciate how well they work when you tap on the doors and hear a solid thud instead of a tinny, snare drum-like resonance.
Even the interior trim panels received some spot treatment on places where large open and unsupported surfaces might be subject to vibration from the stereo’s door-mounted speakers: yup, we’re attempting to take care of all the various noise sources in this project.
What you see next are the sound barriers that were installed between the interior trim panels and the metal vehicle doors. At this point I’d cut the neoprene material and the mass loaded vinyl to fit the doors and also created all of the openings I’ll need for wiring, door & lock controls, etc. and am halfway through bonding the two different materials together. The neoprene is basically a gasket between the mass loaded vinyl and the metal door skin to remove any resonance between the rigid, dissimilar materials.
Once all of the Noico and butyl rope was installed in the doors, the doors were sealed back up with the factory foam covers and plastic vapor barrier before the sound barrier panels were attached to the door using strips of velcro and speakers to hold them in place.
The real challenge was reinstalling the plastic, interior door panels now that there was an extra 1/4″ layer of semi-rigid material sandwiched between the trim panel and the door skin. The latter required trimming various plastic support pieces molded into the trim panel to get everything to fit. I’d started to punch holes in the MLV for the posts before it dawned on me; there’s nothing sacred on the original door panels. These sound control materials are never coming back out of the doors.
Anyway, I suspended my work around 5:00pm and planned to resume work on the headliner, floor, back wall, riser and other smaller areas such as the B/C pillars and kick panels in the footwells.
We got a sampling of how the sound insulation worked when we went out for dinner around 6:30pm on Saturday and were pleasantly surprised at how just the door treatment’s reduced the noise inside the truck.
Installation Day 2: Removing the Interior of the Truck
On Sunday morning it took a full 3 hours to remove all of the seats, plastic trim (other than the door panels which remained intact — carpet, carpet padding and headliner. We had a noon-time appointment that took me away from 11:30am until 2:30pm.
The headliner was not easy to work around as once you have it down there’s no way to get it out of the truck so everything had to be worked around the headliner. With the headliner down, I installed the Noico / CLD tiles on the underside of the roof and some melamine foam between the back ribs and around the perimeter of the moonroof. Sadly, there wasn’t enough room to put the melamine forward of the rear dome light / 1st cross member as that’s how far back the moonroof goes when it’s fully retracted. After reinstalling the headliner I finished installing the CLD tiles on the back wall, riser, floor and B & C pillars and started to lay out the neoprene / CCF layer which I’ll tailor for the install and then use as the template for the mass loaded vinyl.
I also chose to loosen the shifter, parking brake and all of the other hardware on the tunnel so I could fully enclose the transmission tunnel with the neoprene and MLV as I am certain that’s where a lot of the mechanical noise is coming from.
Installation Day 3: The Rest of the Interior & Reassembly
Today was crunch time for getting the sound insulation installed in the cab of the truck; I did not want this to drag out into a fourth day. With that in mind, I was up and at it at 8:30am, working until noon when I had to run out and buy more Kerosene for the space heater that allows me to do this type of work in the garage during cold weather. Yup, it may be 20°F outside, but it’s 70°F in my garage when the space heater is running.
It was around 2:00pm when I got back to work having had some lunch after returning with the Kerosene, filling the heater and then letting it re-warm the garage. I was actually feeling pretty good about how much progress I was making having figured out how to work with the very heavy, awkward to handle and fragile mass loaded vinyl. By dinner time I though I’d have the truck buttoned up by 8:00pm or so that night, and by buttoned-up that literally meant put back together.
Sadly, I ran into an issue that set me back a good 2 hours as I had to rework the back wall treatment before I could reassemble the interior trim. After that I ran into another issue when I was installing the seats on the now 1/4″ to 3/8″ thicker floor coverings in the truck. Yup, there really wasn’t an extra 1/4″ of room for anything in the Toyota’s engineer’s designs and that meant every interior panel and part had to be carefully reinstalled and, in some cases, materials that I’d installed had to be trimmed-back or modified to allow the original parts to be re-installed. The next impact was not getting the truck finished until around 11:30pm, and then spending another 1/2 hour cleaning up the garage and putting everything back in its proper place. Yes, I could have left it a mess and cleaned it up in the morning… no, wait: there’s no way I could do that. My OCD tendencies are just too strong!
1. Those silver “tiles” are installed to provide vibration dampening / resonance control. They give the vehicle that solid sound by eliminating or soaking up things that would otherwise cause the sheet metal or structure to hum, rattle, buzz or echo.
2. A view of the Noico tiles up front, noting I would have normally applied more of the tiles but there was already a lot of factory-applied “tar” on the floor of the vehicle. So, most of what I put down was placed where there was bare, untreated sheet metal.
4. And here’s the floor and tunnel covered with a layer of neoprene and mass loaded vinyl, about 40lbs worth. The strips cover breaks in the seams where the rigid material had to be “shaped”. I’m hoping to get some big transmission and driveshaft noise reduction out of the sound proofed transmission tunnel.
5. And now with the factory carpet pad reinstalled. Yes, there’s some Gorilla tape on there mending breaks I created to get the pad out: they build this stuff into the car.
6. And the sound curtain on the back wall, riser and storage bin. Sadly, this was one of the “you’ve got to be kidding me” moments when I realized I’d put too much material on the rear wall which interfered with the C pillar panels. I recovered, but it added a good hour and a half to the project.
And here’s the interior all back together again. Here’s hoping it was a value-added use of my time and resources. There’s not really any way to tell that the insulation was added unless you know where to look for clues.
It was a long day, to be sure. Thankfully, the truck went back together without any left-over parts and when I put battery power back to it everything worked. As for how much of a noise reduction I may have achieved, that’s TBD. I’ll be running errands tomorrow and will see how the current readings compare to my baseline check from a few weeks back.
Having never done this before, I had a bit of a learning curve and a few “you’ve got to be kidding me” moments. And, I will say that Toyota did not leave a 1/4″ of extra space anywhere, so a lot of interior parts now fit like that perfect pair of jeans after Thanksgiving Dinner.
On the bright side, I’m pretty much done with all of my planned tweaks to the Tacoma. All I need to do now is finish working through a couple warranty issues with Toyota, most notably my rear-end noise. It will be interesting to hear how that sounds after the insulation installation.
Sound Control / Observed Results
As a follow-on to the Sound Insulation material installation, Tuesday was the first time I had the truck out with both the door and full-cab treatments. Let me just say right up front, if you expect to yield Lexus LS – level noise control you will be disappointed. If you expect to simply reduce “all cabin noise” by 50% again, you’ll be disappointed. However, if you are looking to eliminate a LOT of high-frequency mechanical noise, a LOT of high-frequency road and external noise and have a far more relaxing driving experience with better sound production from your sound system and/or the ability to carry on a conversation with your travel companions at a normal discussion volume, you might be pretty happy. I’m pretty happy.
Observed Results: The butt-dyno yielded the empirical results cited above, in terms of how much sound pressure in decibels (dBA) changed due to the addition of the sound insulating materials here’s how it looks at first glance bearing in mind that I’m using the same $13 sound level meter to record ambient noise.
So, referring back to my entry on 30 December for the baseline, here’s where it was:
- Right Front / Passenger Seat: It ranged from the mid-40’s at idle to a high of 70.5 dBA at highway speeds, hovering mostly in the low- to mid-60’s at just about any speed above 40 mph. Mid-50’s below 40 mph.
- Right Rear Seat: It ranged from the high-30’s at idle to a high of 80.5 dBA at highway speeds.
- Left Rear Seat: Similar to the right, but the high was only 76.4 dBA, which could be because the fuel tank sits on the left side of the truck and likely attenuates some of the rear road/tire/axle noise.
For today’s drive, here’s what I found:
- Right Front / Passenger Seat: It ranged from the high-30’s at idle to a high of 63.5 dBA at highway speeds, hovering mostly in the mid- to high-50’s at just about any speed above 40 mph. High-40’s to low-50’s below 40 mph.
- Right Rear Seat: It ranged from the mid-30’s at idle to a high of 70.2 dBA at highway speeds, hovering in the low- to mid-60’s most of the time.
- Left Rear Seat: Didn’t bother checking, as the results were presumed to be consistent with the right side, front & rear passenger seats.
Bear in mind, just at low idle with the windows close these trucks normally develop about 42-45 dBA, which is on par with the noise in your average kitchen with appliances running. We have an air purifier / ionizer in our kitchen that raises our ambient noise level to about 50 dBA. A hand-clap in the kitchen will score about 85 dBA. So, this is the sound pressure range we’re dealing with in the cab of the truck. As another point of reference, your heater fan will generate a lot more dBA than your sound system when played at normal listening levels. To move the sound meter above, say 80 dBA, in the cab of the truck moves the music into the really loud / turn that shit down level.
Bottom Line: Getting a 10% reduction in sound level dBA is not insignificant. Moreover, if you bound the observed dBA range from the baseline test between just the low to high observed levels to something on the order of 35 to 45 dBA, seeing reductions at the high end of 10 dBA is about a 25% reduction to the dynamic sound pressure levels in the cab.
My Analysis: Again, going on what I learned during my research on this subject which is best summed up in a very concise article at a practical level on the Sound Deadener Showdown website, it takes more than just using one type of material or technique to attack noise in a vehicle. Going from my experience in other areas dealing with wavelengths, you’ll always be hard-pressed to do much about low-frequency noise in any vehicle application: low-frequency = long bandwidth and there’s just no room for thick sound deadening materials. It’s those low frequencies that typically drive a lot of the measured dBA’s, but those frequencies are not the ones that typically get on your nerves or that you’d like reduced: it’s the higher, shorter bandwidth frequencies and that’s where this particular application of 25% vibration dampening with something like Noico 80 Mil or Dynamat & Butyl rope + >80% blockage of airborne sound using 1/8″ (1lb per sq in) mass loaded vinyl (MLV) bonded to a decoupler like 1/8″ neoprene will yield some good results. 100% blockage just isn’t possible in an automobile cabin for a variety of reasons:
- Certain structures and shapes just don’t lend themselves to applying a 1/4″ layer of semi-ridged MLV & neoprene such as the raised reinforcing ribs under the front seats of the Tacoma.
- The material must nest in behind interior trim pieces to allow the outer perimeter of the trim as well as fasteners to contact the sheet metal, often time requiring cutting down molded-in plastic spacers on trim pieces or just surrendering to leaving untreated structure behind difficult trim pieces, e.g., the back corners of the double cab and footwell kick panels.
- Certain spaces behind trim and under carpet do not allow for any additional material stack height such that full, side-wall-to-sidewall floor coverage isn’t possible, e.g., I had to trim back the MLV from under the B-Column trim so that it could be reinstalled and there is zero clearance between the seats and transmission tunnel such that even the seat mounting rails had to be pressed down into position to get the mounting holes aligned with the threaded bosses in the floor. The plastic storage bin is still a work in progress where hopefully compression under the rear seats will continue to push the bin further into the sound control materials to reduce the stack height such that the pressed-in fasteners will actually hold tight.
- Many sheet metal surfaces are simply not accessible / practical to treat due to other structure, wiring, control and related equipment, e.g., firewall behind the dash, roof panels on trucks with the moonroof.
- Windows are the true limiting factor; they’re like screen doors for all but the higher frequency noises, they reflect & amplify all noise within the cabin and there’s no practical / affordable way to treat them. Case in point, just opening the moonroof shade increases the observed dBA by 5 dBA.
- Just the overall difficulty factor / limitations of the materials in general. I’d score this type of installation as a 7 or 8 on a scale of 10 for event the most experienced do-it-yourself types. None of skills or tools required to full disassemble and remove the interior of a vehicle are overly complex. They just require patience, research & reference materials so you don’t tear-up or short-circuit anything, a good memory or detailed photos to aid in reassembly and prior experience working with automobiles in general and interiors, such as having done stereo system installations, etc. As for working with the sound control materials, no real experience is needed for Noico / Dynamat installation: it’s even easier than putting up wallpaper, which is also true of Butyl rope. The MLV and neoprene requires a different set of skills and experience working with auto or some other type of upholstery, building speaker boxes, etc. But, if you’ve done auto restorations or resto-mods, it’s not a big deal: it’s just work.