Sound Damping a Cab

[GPintheMitten]

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]

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]

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]

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]

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]

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]

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]

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

 

[Travelover]

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.

 

[GPintheMitten]

Ok thanks travelover. I'll try some of of these ideas. If I don't get enough reduction I'll look for body mounts. Another guy used some mounts.

 

[the old grind]

GP, I have most of a twin bed sized 'waffle' foam if you don't mind pink to try it out, esp like on the cab roof or something. I agree with the others that the first few tricks won't show what effect the last few details will. (PM coming..)

 

[GPintheMitten]

GP, I have most of a twin bed sized 'waffle' foam if you don't mind pink to try it out, esp like on the cab roof or something. I agree with the others that the first few tricks won't show what effect the last few details will. (PM coming..)

Thanks for the offer but I'll pass on the pink. Let me know if you want help trailering or loading your rig.

 

[the old grind]

Sure. It's just 'test' foam (lab rat stuff) but expendable as such. Blue WF I have is much better, more dense, but smaller pieces, quantities. Would like to see how your cab turned out. Should I wait 'till you have the BH in hand too?

Haven't been by your place since warm weather (Fall sometime) & a new GF last Spring. My bad for not catching you home or inviting you to see my 10 by now. Will atone as best I can, with some stories and updates on new gear. (she moved on, btw .... whew!)

 

[GPintheMitten]

Stop over any time. I'll let you know when I get home with the backhoe. Probably get it next week sometime.

 

[PILOON]

I played with reducing noise in aircraft a bit.
Sound caused by large surfaces i.e. cab roof can be greatly reduced by taping a big X from corner to corner using self adhesive roofing membrane, Adding a liner with a foam backing also will help. Felt even better.
Rubber grommets wherever something penetrates the firewall helps also.
I鐡 suggest that the underlay material used for laminate flooring would also be a good sound killer, not foam type but the other denser materials.
High pitched sound like turbos benefit from lead shielding.

Bell 206 helicopters used dense quarter inch foam with thin laminate of lead to dramatically reduce turbine noise. The product was self adhesive.

My tractor cab has all these tricks and the noise level is most tolerable.

A cessna I once owned was treated this way and I could actually hear the valves when flying.

 

[locknut]

Some very good suggestions here.When I built my steel cab I couldn't believe how noisy it was-like sitting in a big drum.The roof was 5/8" thick roof underlayment with the bottom covered in gray speakerbox carpet.So,in tackling this problem I employed my old subwoofer building skills to tame the resonance. I added a center cross brace offset around 3" so as to make the two remaining areas resonate at different frequencies.It helped a bunch.


Edit;
I just checked over your cab-looks very nice.I see you have two braces on the roof so the three areas might be reinforcing each other.Three offset pieces may help here.The Plex panels are very large so I think I'd try the X taping thing and experiment with a roll of adhesive backed magnet tape for maximum mass dampener effect.

 

[tman1020]

i just installed a steel cab and was also surprised at how loud it was. mine is also mostly glass so what i did was buy about 6 rolls of 1/2 inch thick x aprox 1 inch self stick foam weather strip and and run it between all windows.then i bought air conditioner foam and used that to fill all little openings around all levers and stuffed under dash. lastly i put foam(kinda like eggcrate foam)around seat well. this all helped a lot i no longer need ear protection.. mine came with a sound deading head liner i think that this is a very large help also. hope this helps

 

[94BULLITT]

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.

The L4240 has a thin rubber mat on the floor, a piece of foam then the floor mat.

I don't know if undercoating or truck bed coating would help dampen the noise.

 

[jenkinsph]

The L4240 has a thin rubber mat on the floor, a piece of foam then the floor mat.

I don't know if undercoating or truck bed coating would help dampen the noise.

Forty years ago in the sound reinforcement business guys would use undercoating on the outside of Altec horns to reduce ringing. The undercoating can help but sure is messy to deal with when taking stuff apart. I suspect the multi layer approach with different materials that Kubota uses will work better to dampen a wider range of frequencies.