DIY Doctor UK DIY Forums

Hello,

I am having a noisy device installed in my attic. This is an inverter and it can reach noise emissions of up to 80dB.
There is no way I have this device in my attic as it stands. I also do not want to spend a fortune in soundproofing my attic.

I thought building a box and putting the inverter inside could be possible. I have of course some considerations to take such as ventilation. For this purpose, the "box" will be against the attic wall (house gable) and I am thinking of having a 4" hole with a fan at the bottom of the "box" to get cooler air in from outside and another 4" hole with the fan to suck out the hot air out from the box to outside.

I have read several articles such as
https://www.diydoctor.org.uk/projects/sound_proofing_in_the_home.htm

and learnt about various materials from

soundproof boards: https://www.noisestopsystems.co.uk/shop/wall-soundproofing/acoustic-plasterboard-15mm/

Silent wall liner: https://www.insulationsuperstore.co.uk/product/jcw-acoustic-silent-board-acoustic-wall-liner-1200mm-x-1200mm-x-275mm.html

MVL: https://www.ikoustic.co.uk/products/soundproofing-underlay/mutebarrier-10kgm2/

Acoustic quilt: https://www.buildingmaterials.co.uk/jcw-acoustic-quilt-5000mm-x-600mm-x-52mm

Acoustic foam: https://www.acoustic-foam.co.uk/

Even acoustic sealant such as green glue https://www.youtube.com/watch?v=UO_NowMgPdY

Weatherstripping Material: https://www.amazon.co.uk/s?k=fowong+d+weather+stripping+white+2+seals+3+8+x+1+4+x+10ft+each+seal+rubber+seal+strip+for+window+insulation+adhesive+door+weatherstripping+soundproof+1+pack+total+20ft&geniuslink=true&tag=expert00f-20

I have also read about how much dB reduction correspond to the perceived noise
for instance from this website's table:
https://www.acousticalsurfaces.com/soundproofing_tips/noise_reduction.htm

A 21dB sound reduction will correspond to around 70% perceived reduction.

However, I have struggled to figure out how "thick" the wall of the "box" must be so from outside the box the sound is around 20dB or less.

I thought of having the wall of the "box" made of layers of a mix of some of the above materials. for instance:
27.5mm thick Silent Wall Liner + a 4mm thick MVL + 27.5mm thick Silent Wall liner

The box will have a wooden frame where I will place the different sound barriers. I will use the acoustic sealent between each layer and in the junctions/intersection. This will be done on the 6 sides of the "box".
There will need to be some holes for the electrical cables and I could use the green-blue around those holes.

I will need a door, made with the same principle and use some Weatherstripping soundproof, I guess

I would really appreciate some feedback on the feasibility and how to ensure that the "box" will reduce the noise of the device to the level I wish to reach. In other words, I don't want to hear the inverter from the bedrooms just under.

Are there other points I should consider that I have missed until now?
How do you calculate the efficiency of sound protection to ensure the box will be thick enough with the desired effect?

Thank you very much in anticipation for all the experts out there willing to help a newbie like me.

Add mass to the walls, floors, and ceilings: Adding mass to the walls, floors, and ceilings can help reduce low-frequency noise by absorbing and blocking sound waves. You can do this by using materials such as mass-loaded vinyl (MLV) or heavy-duty acoustic panels.