I have been experimenting with sound deadening lately out of necessity. With the old air-cooled motor, the sound of the engine running was somewhat endearing and only left a slight ringing in my ears after several hours on the interstate. With the TD engine, it's a whole new, much noisier world. The unholy racket coming from the engine was unbearable and I'm sure would have done permanent damage to my hearing on long trips. My sound meter was registering over 100db in the drivers seat.
First I filled the cavity behind the rear seat with pillows, blankets, old clothes, towels, etc. and put two pillows up against the C-pillars. This did not help much at all.
Next I covered parts of the walls and floor with Q-pads. I also removed the paneling, stuffed 1 gallon freezer bags with pink insulation and used them to fill the cavities, then replaced the paneling. I also put the heavy rubber floor mat back into the cargo area followed by a layer of carpet jute and then a layer of carpeting. Those changes resulted in the nice thunk-ing doors that Kelly mentions and a slight reduction in noise level, but still way too high. High enough that I was wearing headphones, except that they didn't work because the noise was a low-frequency drone that went right past them.
Next I removed the front transaxle mount and made a new one that uses a lot more rubber. This made a big difference at highway cruising speed but when I push the RPMs up to passing speed, it is still way too loud. Fortunately the noise is tolerable if I hold it to no more than 62mph. Still way louder than a stock air cooled motor though.
Finally I had a friend sit in the back of the bus and listen for noisy spots. Surprisingly, most of the noise was coming from the floor just behind the bulkheads. There were already Q-pads in this area. I went to Home Depot and bought 8 bags of topsoil and arranged them strategically to cover the entire floor. Bingo! I could hear myself think again. I considered leaving the dirt in there, maybe planting grass as a floor covering but the 320lbs of added weight was a little excessive. I took out the dirt and bought a sheet of 3/4" birch plywood which I will attach to the floor over the Q-pads and under the carpet jute. A guy on another list did say that the biggest reduction in noise in his bus was when he installed a hardwood floor so I'm hoping it will come close to the noise reduction of the topsoil.
I figure that if I put the stock aircooled engine back in my bus now, I wouldn't be able to hear it over the wind noise. But I will never know for sure.
-David On 4/11/2011 1:41 PM, kelly dosch wrote:
Well I can't tell a difference yet, but I have a lot more work to do. I need another roll to do the entire floor. I also want to put that silver foil bubble wrap under the carpet. When the AC is running you can feel a LOT of heat rising up off the floor. All that will have to wait until after The Classic.Just four more days!!!! WEEEEE! Woop! I just piddled a little. --- On *Sun, 4/10/11, Cari Smith /<cariandpaul@xxxxxxxxx>/* wrote: From: Cari Smith <cariandpaul@xxxxxxxxx> Subject: [tcb] Re: Sound Dampening A Bus To: tcb@xxxxxxxxxxxxx Date: Sunday, April 10, 2011, 9:11 AM Cant wait to hear your road test resultsOn Apr 9, 2011 11:57 PM, "kelly dosch" <kellydosch@xxxxxxxxx </mc/compose?to=kellydosch@xxxxxxxxx>> wrote: So I just bought a roll of sound dampening stuff, started installing it on my bus and thought I would share my results, in case any of you have considered it but were not sure if it was worth the trouble. First, let me just say, it is. Holy crap. There are a lot of sound deadening products out there, but I just went with a cheap roll of Window Wrap from the lumber store. Same crap, lower price. It is a film of some kind of rubber/tar compound on a foil backing, peel and stick. Only about 1 millimeter thick and the sales person assured me it won't melt and run even at the high temps in a parked car. One $20 roll is enough to do all your doors and rear hatch, over the engine and maybe under the Z-bench. All that bare metal in a bus just picks up vibrations and reverberates it everywhere. This gooey film absorbs and dampens those vibrations. I was skeptical, but I tried it anyway because I was tired of my doors sounding like slamming the lid down on a dumpster every time I closed them. It was making me wince. Well. Now my door slams shut with a wonderfully satisfying *thunk* and no tinny reverb. It gives the illusion of solidity and I don't care if it is illusion or not. It sounds and feels great. What I really did not expect was the stunning improvement of the sound quality from my door speakers. I know this stuff is made to improve your stereo's sound, but I really did not expect much difference. Surprise! It's like I upgraded my speakers or something. And I haven't even done the passenger door yet! I haven't yet tested it on the road so I can't tell how it works on road noise yet. I still have to do the cargo door, passenger door and under the seat. But I can say so far, it was worth it for the muffled satisfying *thunk* of the driver's door and the improvement in the sound of my music already. I will eventually be doing the floor under the carpet for sure! They say a lot of road noise comes from the tranny and to double it up on the floor between the seats. I can't wait to try it but that will have to wait until after The VW Classic.
