Dealing with spray booth noise

Protecting your hearing from the deafening roar of spray booth exhaust equipment. November 15, 2000

I just finished seting up an 8x7x8 Dayton spray booth. This is a used booth made by JBI. It has a 24" Dayton tubeaxil fan with a 2hp 3ph motor. I installed the fan on the top of the booth and ducted aproximately 8' up through the roof with 16 ga duct. This unit is so loud I need ear plugs. I even added a shroud around the duct/fan housing and insulated it. Also layered batt insulation on top of the booth. The belts and pulleys are lined up. Any suggestions?

Forum Responses
I use ear defenders--like headphones without speakers. It's good you're in tune with your environment because otherwise you will lose the tune in the environment (like birds chirping), due to hearing loss. I've seen a few other booths and they all have a droning sound. Some are worse than others. It's good practice to use ear protection anyway.

I installed a 14' x 25' x 8' booth last year. It has a 30" exhaust fan. We have to use ear protectors--it's very loud!! I must say it seems to be quieter now than it was when it was brand new--the motor may have settled in a bit. I think it's the nature of the beast and you have to live with it.

When I took over a paint department there were 3 spray booths that had been in use for years with NO maintenance ever done. Check the fan blades--there may be build up that is causing the fan motors to really "strain". Also make sure the pulleys are lubricated. Be careful of the filter pads--if they're too restrictive you won't get "draw" through them. I suggest you look at compressed stranded, otherwise known as fiberglass.

I've worked in many spray booths in different plants. They are all loud, some louder than others. Hearing protection is your only option. Wear ear muffs or ear plugs or you will be having people repeat what they say a lot. Dirty fan blade or poor maintenance of a spray booth will make them louder but I have been in enough different types of new booths to know that they will always be loud.

From the original questioner:
Thanks to all that responded. I have heard that the Dayton fan was louder than the others. I was also wondering if moving the fan to the roof would help.

The change you are looking for that will reduce the noise is mounting the fan on the roof. I also agree Dayton fan assemblies are louder, and ear protection is a must.

We have a Devilbis booth with 30" duct and fan. The fan has been mounted on the roof and we find that the noise is quite tollerable.

Roof deck is 20' AFF--this may also be a contributing factor.

I drive a 10 wheeler dumptruck as well as build cabinets and I recently learned something. The smoke stacks on my truck had been bent at the top so in an effort to make the truck look better we cut the last 6" off the stacks from 36" to 30" long. This made the truck so loud you needed ear plugs just to drive it. The other day we got some new 48" stacks and guess what, I can hear the radio again. All I did was move the exit point of the sound 18" farther up and it made an incredible difference.

It also might help if you were to wrap the pipe with an insulation of some type to deaden sound.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
The most common cause of excessive fan noise is too small of fan turning too fast. Booth fan noise can be reduced by adding a silencer as part of the ductwork between the fan and booth. Placing the fan on the roof reduces some of the ambient noise, but still leaves the air shear noise in the duct.

Comment from contributor B:
I am a contractor that has been in the spray booth industry since 1981. The new generation of Dayton fans are exceptionaly noisy. Roof mounting will do little to help this, since the duct will act as a megaphone and the sound will come tunnelling down anyway. The answer for all of my customers with sound level issues has been to install duct liner in the plenum (the plenum is the box behind the filters). This is a 2" batting material sprayed with a rubberized coating and should be installed floor to celing on all 3 walls of plenum. This material is avalible from most ducting and HVAC supply houses. This alone can do a world of good, but there is more noise reduction to be had. For you who that want to get that last little bit out of your system, here we go.

First let's look at our problem. Where is the noise coming from? Down the duct? Of course. The answer is simply to hang a sound target below the duct opening. It should hang down at least 1 duct diameter so it does not restrict air flow and be about 3 duct diameters wide. A piece of ribbed sheet metal with flat bar hangers works fine. Next, line the upper side (fan side) of the target with our friend, duct liner. Both of these modifications have worked for me and my clients and I have brought sound levels down from upper 90 dB to a tolerable mid 70 dB.

The old DeVillbiss fan had very little pitch to the blade, but the pully ratio made the final drive speed much faster. This equals a quiet fan that can't overcome static pressure losses (dirty filters) very well.

That would account for the quiet environment that you are enjoying now, but keep those filters changed! Some of you guys with the new generation Dayton are tempted to pulley them down... don't do it! Booth performance will take a drastic nosedive. Those fans are designed to pull through heavily laden filters.