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TLD



718 posts

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#272879 22-Jul-2020 10:40
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I am currently building an MDF box to reduce the sound from a compressor.  It uses 12mm MDF lined with carpet.  What is concerning me is how much sound will escape from the cooling fan port (120mm circle) and the inlet holes for the fan circulation.  I am wondering if I add some sort of convoluted tunnel to inlet and outlets, if that would make a difference?  

 

This sort of thing

 

 

I am aware that speakers use ports to modify bass response, so would lining such a port with non reflective surface fix that?  Or are there other and better ways to reduce sound emission from a cabinet via a cooling fan outlet?  

 

Incidentally, I measured the compressor noise using a phone app at 90db, and then again when inside the cabinet, but with an open front, and it was actually louder at 92db.  I'm picturing acoustic guitars that use their internal volume and port to amplify, and realising this might be more complex than I initially realised.

 

 





Trevor Dennis
Rapaura (near Blenheim)

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  #2526974 22-Jul-2020 11:06
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Don't do anything to make the airflow convoluted!

 

Most cheap compressors barely have enough airflow to operate with any sort of duty cycle.

 

You'll find a lot of noise is from the valving, a decent intake muffler will help there.

 

I've installed one, and made a box lined with (fire rated) expanded foam insulation that reduced incidental noise on a friend's large, upright, high speed compressor.


mdf

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  #2526996 22-Jul-2020 11:36
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Have a look at the Dust Sniper. I haven't built a complete one, but have repurposed some of his ideas/recommendations for other projects. The "Forbidden Cork Forest" could be something for you to have a look at.


 
 
 
 


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  #2527059 22-Jul-2020 12:47
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It all depends on what level of noise reduction you want.

 

My (2 cents worth) suggestion is a fully sealed box built with 25mm high density chip board (if you can still get it).

 

Perhaps line the box wirh carpet as you are doing.

 

Vent the box with a 50mm hard wall pipe to a location well away from your quiet area.

 

 





Gordy


TLD



718 posts

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  #2527098 22-Jul-2020 13:46
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Sidestep:

 

Don't do anything to make the airflow convoluted!

 

Most cheap compressors barely have enough airflow to operate with any sort of duty cycle.

 

You'll find a lot of noise is from the valving, a decent intake muffler will help there.

 

I've installed one, and made a box lined with (fire rated) expanded foam insulation that reduced incidental noise on a friend's large, upright, high speed compressor.

 

 

I've seen a video where they built a silencing system for the intake. I have a twin cylinder Remington from Mitre 10 which has plastic filter/suppressors on the intakes, but precious little room inside the cabinet I've made to make something more substantial.





Trevor Dennis
Rapaura (near Blenheim)

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  #2527139 22-Jul-2020 13:50
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TLD:

 

 

 

I am aware that speakers use ports to modify bass response, so would lining such a port with non reflective surface fix that?

 

 

Nope. Sound isnt stopped by non reflective surfaces. (high freq is absorbed somewhat by carpet etc, but thats not going to help you much)
In your pic, think of the air in that ~maze~ as behaving like a piston of air . That ~maze~ is just seen as a longer tube by lower freq sound (eg transmission line speaker box )

 

Also , the lower the freq the harder to reduce the sound level (sort of) . Thats why year hear cars bass speaker thumping from quite a good distance

If you build the box big enough (full height to the ceiling) , and dont run the compressor for long , cooling wont be such an issue .
You could force in cool air when its not running

 

Also isolate the compressor from the ground (thick rubber ?)
What might help is smaller in & out cooling holes .

 

And , with a fan, you need incoming & exit air ports , so thats 2 holes . :-)

 

 


TLD



718 posts

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  #2527150 22-Jul-2020 13:56
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Gordy7:

 

It all depends on what level of noise reduction you want.

 

My (2 cents worth) suggestion is a fully sealed box built with 25mm high density chip board (if you can still get it).

 

Perhaps line the box wirh carpet as you are doing.

 

Vent the box with a 50mm hard wall pipe to a location well away from your quiet area.

 

 

I am not trying to make it completely silent.  Just minimise the sound as much as is practical.  I bought a DeWalt job site saw right after lock down as the Menz Shed where I normally use machines was shut.  The saw makes a dreadful row and I worry that the compressor might prove to be the last straw for my neighbours.  Especially if I forget to turn it off at night, (although it doesn't lose any pressure overnight so far, but that might change with time.

 

I'll check out the Dust Sniper link.  I'm already wishing I'd started this thread before starting the project, as I might have relocated the fan.  I'll still bare that in mind for the sake of replacing a not too big panel, so thanks for that idea guys.





Trevor Dennis
Rapaura (near Blenheim)

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  #2527153 22-Jul-2020 14:02
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Maybee something like this , fixing the cause rather than the symptoms
https://www.youtube.com/watch?v=cIkJJLZo0h8

 

or this seems to work better than I would have believed
https://www.youtube.com/watch?v=OxhK-aV_8y8

 

My compressor is also very noisy for such a small unit .

 

 


 
 
 
 


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  #2527164 22-Jul-2020 14:32
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TLD: 
I worry that the compressor might prove to be the last straw for my neighbours.  Especially if I forget to turn it off at night,

 

Put it on a cheap time clock, on at 08:00, off at 22:30?


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  #2527223 22-Jul-2020 15:59
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Acoustic barrier? Perhaps sound insulation cell or upgrade a wall or room, using sound insulation products from hardware store.

 

Upgrade fence to neighbours with Acoustic fence design principles.   





:)


TLD



718 posts

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  #2527273 22-Jul-2020 16:19
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fearandloathing:

 

Why carpet? try automotive sound deadening 

 

https://www.jaycar.co.nz/heavy-duty-sound-barrier-damping-material-improved/p/AX3680

 

https://www.jaycar.co.nz/butyl-based-sound-deadening-material/p/AX3687

 

 

Cost.  I had carpet in the roof space.  I'd seen the Jaycar panels, but I'd need four.  So far the box stands me at $50 for timber and $35 for the mains fan (from Jaycar here in Blenheim.)  So far I have the box fully enclosed and 3/4 lined with carpet.  The phone app shows 87db with the fan hole uncovered, and 85-86 with it covered up, so a chunk of noise is coming through the fan hole which is what I was worried about.  I might still take the Jaycar route later on as it would be much easier to work with those panels.  It has been at least a semi nightmare squeezing in the enclosure panels with carpet stapled to them.

 

I'd seen the intake silencer video.  It reminds me of many (many) years ago around the time of the Mk2 Cortina, and how noisy the 1600 crossflow was with the air filter removed.  (I know the Mk2 originally had the 1500cc engine).  Unfortunately I don't have the space for such a solution, either inside or outside the box.  An interesting idea though.

 

Thanks for all the suggestions guys.





Trevor Dennis
Rapaura (near Blenheim)

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  #2527294 22-Jul-2020 16:53
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You have a noise situation that I assumed was just for you in your workshop.... and you have a saw too as well as the compressor.

 

Keeping the noise down to reduce annoying your neighbours is even more challenging.

 

If your workshop is of light construction materials then you do not have effective wall noise attenuation.

 

A concrete block workshop could benefit from sound absorption linings.

 

If you wanted to go all out with Geek stuff you could consider Active Noise Reduction.... the sort of techniques used in noise cancelling headphones and to reduce noise inside cars.

 

There are some good topics online on Active Noise  Reduction. One example here..   https://www.youtube.com/watch?v=--c0tiIZG6o

 

But as your concern is mainly with your compressor bring left on, then as others have said... a time clock may be your cheapest option.

 

I was faced with getting a new compressor recently.... some options I looked at had noise levels as high as 96dB.... but I opted for a silent (69dB) Tooline AC1024OL. (still waiting for delivery) 

 

 





Gordy


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  #2527674 23-Jul-2020 11:33
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Gordy7:

 

It all depends on what level of noise reduction you want.

 

My (2 cents worth) suggestion is a fully sealed box built with 25mm high density chip board (if you can still get it).

 

Perhaps line the box wirh carpet as you are doing.

 

Vent the box with a 50mm hard wall pipe to a location well away from your quiet area.

 

 

I'd suggest that *low* density board for the box would be better. A double-walled box would be even better. Fill the gap with low density foam rubber or egg cartons or carpet. You want lots of transitions from air-solid-air to absorb the sound energy (i.e. convert it to heat), and minimal solid paths from inside to outside. So probably a flexible tube rather than hard wall pipe for ventilation and air inlet and outlet.

 

Or evacuate the box to a vacuum. ;) Put the pump that does the evacuation inside the box. (In case anyone seriously considers this: NB that your compressor probably vents to the air when it stops/starts, and measures pressure relative to the air it's in.)

 

 


TLD



718 posts

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  #2528818 25-Jul-2020 23:51
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I thought I'd report back after getting it finished, or maybe the first version.  The sound level has come down from 90db to 84db, which still sounds loud to me.  I ended up porting the fan after all because it was loud all by itself.  What that did was make it quieter, but also take out a lot of its high frequency sound. 

 

The biggest problem is that I boxed the compressor in the corner of my garage workshop.  That's fine when you are near it, but I later discovered that is transmitting a loud, low frequency drumming noise through the walls into the house.  That will definitely not go down well when my wife is doing one of her Zoom meetings.  I didn't line the outside walls, so I can try that.  I'll also try and improve the isolation between compressor and floor.   But not right now...  I'll live with it for a while and see how it pans out.





Trevor Dennis
Rapaura (near Blenheim)

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  #2528829 26-Jul-2020 09:17
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Good report. Difficult to suppress noise. Good luck with the isolation.

 

 





Gordy


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