Fan noise, sound proofing

[the image reaper]

Discount Hydroponics - Duct Mufflers ... if ya got the bucks, or the skill to build a copy (looks like it has plain, old, pink fiberglass insulation inside) :jointsmile:

[cavadge]

Ahhh... fan noise. When I recently fired everything up I wasn't prepared for the amount of noise that inline fan made. I had mine mounted to the ceiling joists, and it sounded like a lawn mower was running in the room upstairs.

First step was isolating the fan from the framing. If you check the "Fans" sticky above I posted a link for inexpensive anti-vibration mounts for ceiling mounting. These work really well. Today I added another pair to the charcoal can filter to eliminate the last of any vibration.

That being done, I still had the noise of the fan itself to deal with. Did find those silencers for $100 a pop, but wanted something less expensive. Found a thread or two on other forums discussing home-made silencers, and after mulling it over, I went ahead and built one. Connected it to the exhaust side of the fan, with about 2 feet of insulated ducting in between.

What a difference!!! All you could now hear is the almost silent whoosh of the air moving. Went back inside, and... damn, still noisy. So I made a second one and put on the intake side.

Ahhhh... silence.... almost. All I can hear now is the fan motor, and my res pump makes more noise than it does.

The setup is - Charcoal can filter --> muffler --> inline fan --> muffler.

Total cost for both mufflers was about $65. A trip to Home Depot and a local crafts store (I went to AC Moore) netted everything needed. Sorry, no pics, but this is easy to make, and looks kind of like those old Cherry Bomb mufflers.

Parts required (this is for a 6" duct) for one muffler. (If you are going to make two, double up on the quantities except for the hardware cloth. And if you have an 8 inch duct, just get 10 to 8 inch reducers and a 10 inch piece of duct).

Home Depot

Qty 2 - 8 inch to 6 inch duct reducers (about $5 ea)
Qty 1 - 2 foot section of 8 inch duct, in sheet form (about $6)
Qty 1 - 5 foot by 2 foot roll of "hardware cloth" (found it in the gardening section, where fencing mat'ls are kept). (about $6)

I don't know why they call it hardware cloth. It's a galvanized wire mesh, with 1/2 inch squares. There is enough material in the one roll to make two mufflers (either size).

AC Moore

Qty 1 - queen size polyfill sheet ($12.99)

Polyfill is the foam-like material used in pillows and as insulation in jackets and coats. The piece I got is not very thick, but folding it over and over until it was about 2 feet long netted over an inch thickness. There is enough material here for an 8 inch duct muffler as well.

DO NOT USE FIBERGLASS!!! Fiberglass will continually shed particles, getting into your HVAC system, all over your house, and of course, in your lungs. We all have better things to put into our lungs...

So here's how to make the muffler.

1) Measure and cut a section of hardware cloth, such that it will form a six inch circle two feet long. I used an old piece of six inch piece of duct as a template. If you don't have one, find a tin can the right size or just measure until you get it right. Better a little bigger than smaller (smaller = flow restriction). The cloth was wrapped with galvanized wire, so I used pieces of the wire to tie the ends of the cloth together. I overlapped about four squares which made it easier.

2) Fold the polyfill so it is about two feet or a wee bit more wide.

3) Wrap the polyfill around the hardware cloth evenly. It will overlap. Leave just a little bit hanging over the ends.

4) Take the 8 inch duct section and fold it around the polyfill. I couldn't get the seam to lock in, so I cut some of the polyfill off until I could get it to lock. At this point you have a 6 inch diameter wire mesh, surrounded by polyfill, enclosed inside a piece of 8 inch duct.

5) Carefully fit the duct reducers to the ends to the duct. I say carefully, because the first one was sticking, I banged on it, and it fell apart. Back to Home Depot. Now one end of the duct is crimped so the reducer goes on fairly easily. The other end is smooth, and won't go. I had a crimping tool on hand, so no problem. You can buy one for about $20 at HD or just cut the end of the duct about a 1/2 inch or so every couple of inches and fold the ends down a little until you can get the reducer on.

6) Apply metal foil duct tape to all the seams.

Done! The finished piece weighs about 2 lbs, and is incredibly efficient. I was truly amazed how quiet the fan is now that both ends are muffled.

HTH,
Steve

[cavadge]

*Update*

I was reworking the exhaust ducting, to tuck it up in the joist bays, and I discovered that the exhaust muffler doesn't really do anything, now that an intake muffler is in place. The bulk of the noise seems to be generated at the intake; once you silence that, you're golden.

So I'm leaving the intake muffler in place, and using the second muffler to quiet the intake of the inline fan I'm about to mount to cool the HPS lighting.

Live and learn. :smokin:

[Smurph]

Dynomat is used for vibration muffling not sound.....

Your best bet is really to buy the soundproofing foam, its like 5-15 bucks a square foot and ideally you dont need all that much of it, just enough to muffle the sound, u could use it every other square foot or u could just put it around the walls the fan is near to minimize sound deflection. If you know about sound most of the problem is the deflection and reflection of the waves, so all u need is a little bit but in the right spots good luck.

I had a similar problem all i did was moved the fan from one side of the room to the other

Wow. Sound is vibrations. Dynamat WILL cure your noisy fan.

[cmasfca]

Wow. Sound is vibrations. Dynamat WILL cure your noisy fan.

QFT

EDIT: Oops, didn't see how old this thread was:wtf: