Soundproof Enclosure for Exhaust Blower

[Scott Winstead]

On another thread, we discussed some various options for exhaust blowers for your laser. I've got a Grainger/Dayton high pressure blower for my ULS laser that makes a fair amount of noise (84 Db). Unfortunately, it's located close to a common area/walking path that's only about 10 ft. away.

I need to build an enclosure for it that will hopefully reduce the sound by 20 Db or so. I'm thinking a 2 ft. square box out of exterior 1/2" plywood lined with soundboard and then having a foam-backed carpet stapled to the soundboard with some folds to reduce help silence the blower. On the exhaust of the blower planning to use some ductwork to create some form of small smokestack to raise the fumes above the ground and to also reduce the noise that will find it's way out of the exhaust.

Any lessons learned out there with soundproof enclosures? Haven't started the construction process yet - I'm hoping someone will confirm my approach or provide some alternatives.

[Mike Null]

Having retired from the appliance business where we had sound rooms at several of our plants to aid us in the design of quieter products I can tell you that there is no satisfactory answer equal to buying a quieter unit to begin with. Band Aids generally do not work to your satisfaction.

For $250 to $350 you can get a unit that won't make so much noise to begin with and you can save yourself the time and trouble of building something that may not work. Besides, you can probably recover part of the cost by selling the old blower.

If you decide to go ahead I would try to find something other than plywood which just resonates sound.

[Scott Winstead]

Thanks Mike - I'm one of those "stubborn, gotta try it" people. I'm planning using the exterior plywood just as the outer case - the soundboard and carpeting is what is intended to muffle the noise. I live in Phoenix where it seems that every neighborhood has a Homeowner's Association (aka folks that make rules) and I want to keep under the "radar". I figure that my creation will be under $50 - if it works great, if it doesn't I will likely follow your advice.

ULS is pretty specific on the blower and exhaust system (a minimum of 250 CFM under a load of 6" static pressure = 425M3/hr @ 1.5kPa). They specifically state that an in-line air handler is not adequate. They specify that a high-pressure be used to meet the minimum airflow requirements.

[Mike Null]

I used my ULS for 8 years with an in-line blower and it's still working. So's the blower. I did, or tried to do, my homework when I bought my blower. What I found was there are precious few people who can competently address the issue. A rating such as cfm is relatively easy to understand but static pressure as it relates to cfm and specifically to a somewhat enclosed area such as a laser cabinet is a whole new issue.

I spoke to one of the engineers at the mfr. of my blower yesterday and when I mentioned 6" of static pressure his remark was "that's absurd". I do not have confidence in ULS or any other laser people to know about blowers. I believe they believe in the overkill strategy here.

Is there a chance you can install a variable speed control on your blower. Then test it at various speeds.

[Tom Majewski]

Hey Scott,
I have some tips for you.

I used to be the CAD guy at a company that specialized in soundproofing recording studios ( http://www.soundhousedesign.com/ ). We isolated a lot of the tools in the shop.

Try to get something like these Owens Corning fiberglass panels - http://www.acoustimac.com/products.asp

They are 10X beter than carpet. Use 3/4" plywood instead of 1/2". Also look for rubber isolated feet for the bottom of the blower frame. Try to get something aproaching these - http://www.kineticsnoise.com/hvac/floor.html

I realize this is more money than most solutions, (more than I would put out of MY own money), but just wanted to show you what the top end would be.

Tom

[Scott Winstead]

Mike - if you don't mind me asking, who is the maker and model of your in-line exhaust blower. I'd like to check it out and might do a side-by-side comparison/test if the cost isn't too prohibitive.

Thanks!

[Joe Pelonio]

Here's what I have. I was kind of shocked to see how much more it costs now, I paid less than $300 for it 2-1/2 years ago. It's really quiet, once you get the mounting bracket and plumbing secured. Any noise was from vibration of the system, not the fan itself. All you can hear is the air flow, and outside where the vent ends it's totally silent.


Fan,Duct,10 In
In Line Duct Fan, Maximum Speed 3000 RPM, Speed Control 5C203, Maximum Power 211 Watts, Inlet/Outlet Diameter 9 7/8 Inches, Duct Diameter 10 Inches, Sones @ 0.5 Static Pressure 11.6, Air Flow @ 0 Inches Static Pressure 598 CFM, @ 0.125 Inch Static Pressure 580 CFM, @ 0.250 Inch Static Pressure 561 CFM, @ 0.375 Inch Static Pressure 543 CFM, @ 0.500 Inch Static Pressure 525 CFM, @ 0.750 Inch Static Pressure 487 CFM, Diameter 13 1/4 Inches, Width 5 1/4 Inches
Grainger Item #4YM41Price (ea.)$392.75BrandFANTECHMfr. Model #FX 10XLShip Qty. http://images.grainger.com/images/icon_help.gif (http://www.grainger.com/Grainger/wwg/productIndex.shtml#) 1Sell Qty. (Will-Call) http://images.grainger.com/images/icon_help.gif (http://www.grainger.com/Grainger/wwg/productIndex.shtml#) 1Ship Weight (lbs.)14.05Usually Ships** http://images.grainger.com/images/icon_help.gif (http://www.grainger.com/Grainger/wwg/productIndex.shtml#) Today (http://www.grainger.com/Grainger/wwg/productIndex.shtml#) Catalog Page No.3998 http://images.grainger.com/images/mini_catalog.gif (http://www.grainger.com/Grainger/wwg/productIndex.shtml#)

[Mike Null]

Scott:

Here's the web site. Mine is now nearly 9 years old but it seems like I paid about $300 maybe a little less. The model is a K6 which the engineer told me was now out of production although I'm sure there's a replacement.

The information Joe offers is consistent with what the engineer said to me yesterday. He was talking in terms of tenths of an inch static pressure not 6". My unit is smaller than Joe's.
CFM is 267 @.7" static pressure. Noise at 10 sones.

http://www.kanalflakt-us.com/