Making a muffler box for exhaust fan with cardboard box and no tools?

[TheFertilizer]

Well I cut up the box my fan came in with two holes in the side. Well come to find out it wouldn't fit that way, so I had to cut two more and I basically just stuck it back I there with the styrofoam and packing it came with, but it doesn't seem to quiet it much. Even if I put the cardboard circles I cut out back into the box so there's only two holes, it doesn't really make a difference. The box was double corrugated too so I am surprised. Maybe I just need to stuff in more material? I tried grocery bags but they made it worse. The fan wad rated at 75 dB and I am reading it at 59 dB, of course I did r benchmark it before I had it in the box so I am not sure what the real world drop in dB was but my air conditioners fan came in at 57 so I can live with it, especially dialed down, but I am just wondering what I can do to get more reduction in sound.


Does it matter if the fan is surrounded by stuff anyway? Like if I just filled it up with packing peanuts would that make it too hot?

 

[Richard Richardson]

There shouldn't be a problem, even old clothes will muffle the sound.

Can you show us a picture of what you mean?

 

[jonny64]

insulating the ducting also helps

 

[TheFertilizer]

Hmm I tried it without any ducting so maybe that would help with normal ducting.

Best way to explain is thst the two holes on the side were accidents. They do make it easy to stuff things in though.

 

[Richard Richardson]

I wouldn't worry about the holes. If you have no ducting attached, the fan will be loud anyway.

 

[TheFertilizer]

Cool I bet it will be pretty tolerable with the ducting and box.

Now I just gotta get ducting. I was thinking about insulated anyway

 

[Weaselcracker]

Thermal insulation isn't the same as acoustic insulation. Basically- in a general sense- to block sound it seems that you want something dense. Drywall works well. I built a baffle box outside at the end of my out vent ducting. Couldn't use drywall because it needed to be waterproof so I used some sort of heat insulation board I had around, since it was very dense and heavy. Without putting much work into it- it got the noise down to an acceptable level and I called it good enough.

 

[Mcjoint]

Are you using variable speed controller?

 

[TheFertilizer]

Are you using variable speed controller?

Yeah and I am hoping to keep it set lower for as much as I can but it gets pretty hot in my house and I don't have good air conditioners, so I will probably have to crank it up at some point during hotter periods.

Weaslecracke, I thought it was stuff with lots of dead air space that muffled sound most. I thought about setting this box into a slightly larger one. That's essentially how they build sound proof rooms. I wonder if vinyl glued onto the inside of the cardboard would be dense enough? I wonder if sand would fall down into the corrugations on the cardboard.

I think for now I should just wait to see how loud it is with ducting attached, who knows it might be bearable. I like white noise at night anyway, drowns out my annoying neighbors.

 

[Weaselcracker]

All I did at the time was a bit of googling - so you are already stretching the limits of my knowledge in this field. Yes dead air spaces do work to control sound- but the material forming the walls of the space is important. Make your house with hollow walls of styrofoam and cardboard- and you and your neighbors are going to get to know each other very well.
Foam is useful for absorbing echo, but has no real value for actually blocking sound. There is something called mass loaded vinyl that's used for blocking sound- so it's possible that regular vinyl is a step in the right direction. There is expensive sound dampening matting sold for lining vehicles and such. It's similar to rolled roofing which we use on houses. In my first forays into silencing my fan, I tried some regular rolled roofing wrapped around it. That worked well but was heavy and clunky.

 

[TheFertilizer]

All I did at the time was a bit of googling - so you are already stretching the limits of my knowledge in this field. Yes dead air spaces do work to control sound- but the material forming the walls of the space is important. Make your house with hollow walls of styrofoam and cardboard- and you and your neighbors are going to get to know each other very well.
Foam is useful for absorbing echo, but has no real value for actually blocking sound. There is something called mass loaded vinyl that's used for blocking sound- so it's possible that regular vinyl is a step in the right direction. There is expensive sound dampening matting sold for lining vehicles and such. It's similar to rolled roofing which we use on houses. In my first forays into silencing my fan, I tried some regular rolled roofing wrapped around it. That worked well but was heavy and clunky.

Heh was actually thanking specifically of that stuff they use on cars, had to change the in-tank filter on mine and the access was under the seat, there's a big vinyl sound proof matt that feels like it's filled with lead lol I wonder where you buy that stuff, I guess I could sacrifice the one from my car but then I am going to be wondering about every little noise I never heard before on the car haha

 

[Weaselcracker]

It's easily available online. Dynamat is one common brand name. It costs $. Somebody lined their car with rolled roofing- such as what we call ice-shield- peel and stick roofing, often used as a temporary roofing while awaiting the real roofing, or as an underlay. Apparently the ice-shield roofing worked almost as well to block the sound as Dynamat, but stunk like tar on hot days.

 

[Mcjoint]

Cardboard egg cartons make great noise insulators.

 

[Mcjoint]

Yeah and I am hoping to keep it set lower for as much as I can but it gets pretty hot in my house and I don't have good air conditioners, so I will probably have to crank it up at some point during hotter periods.

Weaslecracke, I thought it was stuff with lots of dead air space that muffled sound most. I thought about setting this box into a slightly larger one. That's essentially how they build sound proof rooms. I wonder if vinyl glued onto the inside of the cardboard would be dense enough? I wonder if sand would fall down into the corrugations on the cardboard.

I think for now I should just wait to see how loud it is with ducting attached, who knows it might be bearable. I like white noise at night anyway, drowns out my annoying neighbors.

Cheap verible speed controllers make a loud buzzing noise the lower you turn it down. You want to use a variac they they start at around 60$. Verible speed controller use a resistor to slow down the fan which is why is hums the variac actually lowers the voltage to slow the fan down, thus eliminating the buzzing noise.

 

[Weaselcracker]

Egg cartons - or that type of egg carton shape- is useful to control echo and dampen sound- such as the whoosh of the air through your duct. As something that actually blocks sound from passing through- no they don't block sound, but it's a common myth.

 

[AKgramma]

Question for all the experienced growers with this kind of equipment: Do you think the mounting could be the problem? I use either clip-on fans or 6" desk fans set on the floor or on a box and have no noise issues whatsoever. So they are not vibrating the tent or shelving.

 

[TheFertilizer]

Cheap verible speed controllers make a loud buzzing noise the lower you turn it down. You want to use a variac they they start at around 60$. Verible speed controller use a resistor to slow down the fan which is why is hums the variac actually lowers the voltage to slow the fan down, thus eliminating the buzzing noise.

Thanks for that info, I was wondering why I heard buzzing. Didn't bother me just worried me a little.

AKgramma, no experience but I heard dampening mounts help. So rubber washers where they're screwed on somewhere or bungee cords if hung. Those materials absorb the vibrations more than they transfer to the mounting location. I have heard bungee cords recommended for hanging in a tent for that reason, and rubber washers between the mount and the wall if mounted.

 

[Mcjoint]

Question for all the experienced growers with this kind of equipment: Do you think the mounting could be the problem? I use either clip-on fans or 6" desk fans set on the floor or on a box and have no noise issues whatsoever. So they are not vibrating the tent or shelving.

if you use rubber isolators it will reduce vibration. if don't use them,you shouldn't have a problem just a little noisy.