Noise reduction help for a project

[wallfish 16,985]

With such a diverse group of people here on RS I'm hoping someone might have experience with noise/ sound reduction to help me design something for a new type of system I'm now working with. The manufacturer is a small company out of Canada and they have done plenty of R&D for getting their air system to work for what it's designed to do but it's too loud for my customers. It's a small metal box that's 8" W x 12 1/8 L x 6" deep and contains a small DC powered air compressor. The bottom is the air inlet for the cooling fan with four 1 1/2" holes but I believe the majority of the noise comes from the side holes for the intake air to escape. There's two 3 15/16" diameter holes in the box on each side of the compressor. I'm not trying to redesign this whole thing (at the moment) but reducing the level of noise would certainly be helpful. Their solution is using a fake landscape rock (with a vent and flexible dryer hose to the air intake) to cover it and that reduces the noise about 50%. That's fine for some situations but not the 2 I have done so a better solution is what I'm after. Keeping cost reasonable is an important goal but...

 My initial thoughts are to add a small box on each side to direct the noise down instead of directly out the sides and use deflection with some baffles along with something for absorbing some of the noise as well. This will be outside and exposed to the weather so durability is a main concern as well. I'm no sound expert but hopefully we have one among us and I know there are plenty of tinkerers with a wide range of knowledge so any input will be helpful.

 

 

 

 

 

 

 

[ebinmaine 67,275]

After reading this my initial idea is pretty much the same as yours. Some sort of redirection system with absorption is what I was thinking.

 

One thing that comes to mind for me is, why do the side holes need to be so large? Is it possible that the side holes being as big as they are is letting out too much noise? Could the side holes be filled in with solid material and the vents be relocated to a different location?

Or are they that size because they are necessitated for cooling of the motor?

 

 

[stevebo-(Moderator) 8,330]

Not sure how John but foam egg crates like you would have put on a bed to make it softer. Somehow wrap the whole thing. The other great insulator is rockswool insulation. Very dense... 

[AMC RULES 37,127]

Search Dynamat

[953 nut 55,076]

Have you tried bubble wrap?

[Pullstart 62,791]

10 hours ago, stevebo said:

Not sure how John but foam egg crates like you would have put on a bed to make it softer. Somehow wrap the whole thing. The other great insulator is rockswool insulation. Very dense... 

 

Is there room to stuff egg shell foam in the inside?  

 

Not knowing the rest of the install, are there any other pipes hooked to this, or is small tubing doing the rest of the work?  In the turbo world, the blowoff valve is often plumbed to the exhaust to carry noise away too.  I was thinking maybe a wye into another intake tube might help?

[Achto 27,504]

10 hours ago, wallfish said:

My initial thoughts are to add a small box on each side to direct the noise down instead of directly out the sides and use deflection with some baffles along with something for absorbing some of the noise as well

 

I think that this idea would be the easiest to add on. We use insolated intake & exhaust hoods on some of our generators for noise reduction. There is a noticeable difference compared to units that do not use them.

[WHX?? 48,779]

Fiberglass sound batts arranged in some fashion? Is this thing used interior or exterior? In other words does it need weather proofing? How about a sheet metal "cover"  box with sound absorbing foam glued to the inside? Ventilation holes with sound baffles?

[oliver2-44 9,685]

 Insider puttin some sound absorbing material on the ground/ concrete under the unit in the air intake area.  This will reduce the sound from the compressor  hitting a hard surface under it and bouncing/amplifying.   My house Central AC is a vertical unit with a blower fan.  I put a piece of black sound absorbing material on the concrete floor under it. This reduced the blower fan noise amplifying on the hard concrete 

Instead of another box around the unit can you line the inside of the large fake rock with sound absorbing material. If possible Leave a 1or 2” airspace between the rock inner surface and the sound material.  Even if you can leave an air space line the inside of the rock with sound quality egg crate or sound mat.  Soft porous surfaces are your friend

Also consider how the unit is mounted to the floor. Some spring or rubber mounts might set something to consider. 

[Stormin 9,981]

  You mention fitting a small box to the outside with baffles and sound absorbing material inside. Have you room inside the compressor box for something similar as well? Can you double the thickness of the lining inside the box also?

   One thing to think about is you don't want to restrict the air flow to much.

Edited August 22, 2019 by Stormin

[prondzy 3,881]

If you dont mind me asking what is the compressor/box used for (what application, do you have a pic of it in its applied location)? Also what are you mainly trying to quiet intake/exhaust air or vibration/noise from the compressor itself? Just trying to wrap my brain around this one it sounds like a challenge!

[wallfish 16,985]

This box mounts directly to a private water well head casing.( 6" well casing pipe) and it's purpose is for radon mitigation of well water. It will be outside in the weather and elements. The air flow can NOT be restricted since these units are expensive and I do not want to over heat or effect the manufacturer warranty. The problem on some of the installations is, the well head is close to the house so reducing the noise db level would be helpful. It's not an issue when the well head is located out in the property away from the house. It's not super loud but imagine one of those 12v compressors used to fill your tires running 24-7 right outside your window.

 My modification to reduce the sound level needs to be durable and not appear like a hack. It needs to be an accessory which can easily be added or removed and painted black to match the existing finish of the box. 

 

Something like this?

 

 

 

 

[Lee1977 6,642]

Try fasten some drink carriers form you favorite take out place over the outlets. They already have openings .