Sound Damping a Cab

GPintheMitten · Feb 22, 2014

I built a cab this winter. Made out of steel and plexiglass mostly, with a plywood roof. There isnt any sheetmetal on the cab. Its totally covered in plex.

There's a lot of noise in this thing. It is solidly constructed and not rattling but its the engine noise that is amplified in the cab.

What have you guys with cabs done to reduce the noise level? I can put some kind of headliner in and can do something with the floor but the rest is plex. I wore hearing protection when I used it last week but would like to quiet the cab down as well. Any recommendations on what to do to the roof and floor?

Thanks.

zmansmac · Feb 22, 2014

I made a cab for mine with a steel front (with safety glass) and a steel roof. The sides and rear are marine vinyl with clear vinyl windows. I did buy some automotive headliner material which is basically a special 1/4 inch foam and glued it to the inside of the roof. That helped absorb some of the noise. In the summer when I mow I wear earbuds connected to my MP3 player and also use a pair of Peltor noise muffs. But I also take the sides and back off for the summer. In snow plow mode during the winter I don't wear anything for noise because I want to hear when I'm down by the road and when I travel to two of the neighbors that I also plow out. I doubt that there is much you can do to reduce the noise because of the amount of window area compared to the non-window areas that you could install some kind of acoustic foam. Sounds like you did a nice job constructing your cab, but I am curious as to why you used plywood for the roof.

Gary Fowler · Feb 22, 2014

Look at the foam that is shaped like an egg carton. It absorbs sound much better that flat foam. Glue it to any surface that you don't need to see thru and of course the roof.

GPintheMitten · Feb 23, 2014

http://www.tractorbynet.com/forums/build-yourself/300825-diy-cab-kubota-b2620.html

Thanks.

The reasons for my choice of plywood are that I thought it would be quieter thhan sheet steel and something that I could fab and install easier.

Here's my build thread.

chvfrk98 · Feb 24, 2014

Part of it might be too much plexi as well. It is going to reverberate a little more than the frame. Mass is the only thing you can add. You can get some stereo sound deadener and put a few layers on the roof. Ice shield for roofing is a cheap and similar alternative.

8N Ren · Feb 27, 2014

GP check out some stuff called Dyna Mat. Lots of people in the custom automotive stereo scene use it on interiors under carpet, around door speakers, goes on easy with a roller.

Dave M7040 · Feb 27, 2014

When dealing with noise issues, in addition to the points made by others, you need to think of the cab as a boat. A small hole can let in a lot of sound. You need to seal any pathway between the engine and the cab which can be a big challenge. To illustrate, open your car window just a crack and see how much more engine and road noise can come in.
Good luck.
Dave M7040

GPintheMitten · Feb 27, 2014

Ok thanks for the advice guys. Good analogy on the boat. Ive got some holes to fill to float this thing.

Travelover · Feb 27, 2014

I was a noise and vibration engineer in the auto biz for 27 years.

High frequency noise, like diesel cackle, and engine mechanical noise comes through holes, even small ones. Better sealing and absorption materials like a hood liner material on the ceiling can decrease it.

Lower frequency noise, like engine firing frequency is usually structurally borne, meaning the vibration is transmitted to your cab and the large surface areas of the cab act like speaker cones. Isolation of the cab helps (body mounts) and also stiffening and or damping the panels helps. Obviously, you want to see through the clear parts, but in a car these would be coated with a bonded damping material.

Noise cancelling headphones might help a lot.