Road Noise from rear cab vents..?

Will definitely try 'seats up' before the extra insulation. It makes sense. But I like to tinker and will put extra insulation eventually.

 

A big part of it is just the thickness of everything. The new twins are quieter because they are just bigger/thicker. lots of seals on those things.

Tacomas are what they are, little/thin trucks. hard to keep it quiet.

 

It don't make a difference. I keep my Munchkin seats folded up all the time.

 

It is my very unprofessional opinion that the rubber "seals" that Toyota put between the bed and the cab create some sort of vacuum that causes the vents to open. It doesn't bother me too much as I came over from a soft top Jeep with mud tires and pretty much anything is quieter than that. If your other car is a Lexus, I can appreciate your frustration.

Also, when I sealed the vents with silicone for a leak, there was an appreciable decrease in road noise. Mind you, I didn't seal the little rubber flaps closed, but the plastic vent housings were crazy loose so I put silicone around the edges to hold it in place and stop the leak. A little water still sneaks in through the actual vents - as opposed to the waterfall that was coming in from the poor seal - and that is why I think there is a vacuum back there that opens the little rubber flaps.

 

I thought it was a double cab. Didn't realize it was an access cab, it make help a little but prob won't be as much

 

I will take out the vents and take some pictures. Interestingly the little ribs are floating rubber like the dairy section door at Costco. Since they are pliable, I would think they are constantly in motion and creating air gaps and therefore noise.

Currently the noise level change due to my removal of the back seats is astounding. I can hear the water drops from the bed. I can hear the brakes engaging. It's pretty impressive as to how much baffling of noise the basic seat and back do provide. As a test, I tossed a row of pink attic insulation in the back and the noise levels dropped significantly. Obviously, a 2x4 frame is not the answer.

I have some free time next week so I have a little project in mind for fun. I have a decibel meter from my home theatre DIY days. I have reviewed the DIY sound proofing threads and have picked up:

pink rigid insulation http://www.homedepot.com/p/Owens-Co...uared-Edge-Insulating-Sheathing-36L/100320356

radiant barrier insulation: http://www.homedepot.com/p/Reflecti...-Insulation-with-Staple-Tab-ST16100/202851859

bitumen underlay: http://www.rona.ca/en/roofing---self-adhesive-roofing-underlayment

I will go pro the decibel meter on a 2 mile loop that includes highway speed with the empty back. Then I will add each one of the DIY methods and record the numbers.

If someone has access to cheap dynamat, I'll test that too. I suspect the dynamat will provide the best decibel dampening per unit of insulation, but I'm not sure they would be super excited to be part of something like this.

Currently, the naked Taco is running about 78 DB in traffic at 30 MPH. I'll run the test course with the truck like this and see how much work the video / data recording will take. I might get lazy and see if the meter has an average and use that. But fingers crossed for the video.


10 DB reduction is a huge gain. I believe Dynamat has mentioned 10-12 DB reduction. Here is an example video from them. Imagine a classic VW at 115 DB!! https://www.youtube.com/watch?v=m4PcADCh_lI

AS an FYI, here is an example chart that shows the difference between the decibel levels.
http://www.industrialnoisecontrol.com/comparative-noise-examples.htm.

more to come...

 

kevin ..
Happy to see your dedicated interest in this. I will be following closely. What are your thoughts on just stuffing in some home 'pink' roll type insulation. I know its supposed use is for thermal insulation, but it stuff in fairly tightly should work as a sound insulator too, and would be much easier to do. The bare back wall of the cockpit it not very smooth. I can see something like stick-on products like dyna-mat (though probably the best) as being hard to apply..?

For a truck, the sound is actually not all that annoying, but the new Tacoma is otherwise so refined and comfortable, making it quieter is a big plus..

Its ride and handles better than the Xterra I traded in, but noticeably noisier in the cab. Since the Xterra is basically a Frontier pickup with a short covered bed, I thought they would be similar..

 

Probably how dampness gets in my truck under certain weather conditions.

 

I'd be careful with that stuff. Those tiny glass fragments are rough on the eyes and skin. In a windy environment, I'd hate to have the stuff blowing around my cab. Just a thought.

 

The new stuff isn't like the old stuff. Most doesn't even contain fiberglass anymore

 

The flaps only open when there is enough pressure in the cab to do so. So driving with a Window down or shutting a door with the windows closed it will open until the pressure equals out. That's all the vents are for stuffing insulation in them may prohibit this some, but I guess if it's nothing you that bad than it's worth a shot

 

The rear vent flaps are designed so they sit very loosely in the vent housing, you can lightly blow on the flaps and they open up. The flaps aren't going to stop noise from coming into the cab no matter what position they are in. Has anyone tried completely blocking off just one of the vents? I know there are issues when both are blocked off.

 

I had mine blocked off with masking tape for a few days and found that the windows fogged up quite a bit.... The noise was definatly coming in from the sloppy space around the vents AND the rear metal wall of the cab....

After sealing around the vents and applying sound deadener to the rear of the cab, I had about 40-50% reduction in noise... I run with the seats down 99% of the time... Even better with seats up..

See my previous post here at post # 105.....

https://www.tacomaworld.com/threads/cab-noise.397446/page-6

Good luck...

 

Well that's just wrong. Before we know it, Japanese trucks will be made in Mexico...

 

over60 (so am I..)

I like the idea of spray-on insulation. Thanks

Did the spray block any of the mounting holes to hinder re-installation ?

 

I noticed something else that might help. When you look where the bed meets the cab on the sides and top, you will see a small gap. On the sides Toyota has put a piece of rubber trim to make the gap more pleaseing to look at. Now go under the truck and look at 2" gap between the bed and cab just above the muffler. With the small gaps on sides and above this area acts as a sound collecter and brings the muffler and road noise straight up to the rear vents. I took a 5 1/2 " x 36" piece corigated plastic (looks like cardboard but is plastic) and put in this area, extending over the gas tank and towards the right side of cab. There is a 3/4" wide flange that runs along the cab, I used three metal roofing screws and secured the plastic to the flange. Reduced sound. Sorry no pictures.

 

Another good idea...

 

NO...I put masking tape over them just in case, but it was not needed... the plastic "thingys" just pushed thru it when I re-installed the OEM stuff...

The most critical, In MY opinion is sealing the AROUND vents....(they are so sloppy..1/4" play inward/outward).. If I was to do it again...I'd use silicone from a calking gun all around them. I just used the product shown and it dries hard... might be good to have the "flex" of silicone to keep from cracking loose in future..

Might be a better product out there, but in the boonies here, that was the only thing I could find...

Good luck..

 

^^ Thanks, I have been searching for other types of spray on-insulation as addition to the one you used. If I find anything real interesting, I'll post a link..
Lots of helpful posts here...

 

Thx.

I wouldn't use pink as I don't think it would be durable.

From my understanding about sound waves , sound isolation is achieved two-fold :

1). High freq noises. Higher range noises like squeaks and squeals and vibrations. High freq can be soundproofed by stopping the airflow. I think this is one way the dynamat type product work. Acting like a seal. So the vents in the taco break this rule

2) low freq noises. This is bass. Lower range like tires on pavement and engine noise. Airflow proofing won't be enough. The lower range has longer wavelengths and will go through insulation. I think dynamat uses a bitumen layer to deaden the lower frequencies. But the product is not that dense so it can only do so much.

My assumption is that the difference between dynamat and a day is that the deadening layer in dynamat is quite dense. So it's great when you need to add a layer between the frame and the panels. But I think that a cheaper alternative can be used when you have the flexibility of depth.

Since I ripped out the back and will put an aluminum panel to hang recovery stuff.

So test 1 will be to see how quiet I can make the cab. Test 2 will see how much reduction per mm of insulation. There will be a sweets pot here.

I'll run a couple of tests with the vents first to see how much of a factor it will play.

My money is on 1/2 inch rigid insulation with some tuck tape to air block stuff.