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DIY MVHR Acoustic Silencer


Iceverge

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We're in now with 7 months. I've never been chuffed at the noise of the MVHR at night in the bedrooms. We had a flexible acoustic silencer from BPC but it's been of limited value so I decided to rig my own scrappy attempt. 

 

Firstly it's in an awkward corner so I had to go for an irregular shape. 

 

MDF and airtight tape was the order of the day. 

 

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Some discarded foam formed the maze for the air to transit through the first level. All held in place with spray adhesive. You can see the entry hole at the left of the box. 

 

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Capped with another layer of foam.

 

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And a sheet of MDF all taped up shortly afterwards. A hole for the air to enter the second layer. 

 

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The second story was a little different. I drilled 160 18mm holes (yawn, boring!)  and offset them to try and diffuse the noise a little. The first layer seemed good at getting rid of the 375Hz and 7500Hz noises that my phone recorded but not the 53Hz, after some googling of car exhausts the many small holes method seemed like a good idea. Mostly fingers crossed and little science involved.  

 

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I shoved it into the corner and connected the ducts up. (Supply enters straight from the top of the MVHR unit and exit is above it in the roof.  I might enclose it at some stage if I can be bothered. 

 

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And hey presto. 

 

I took the opportunity to use my iPad to do a sound level recording before and after with the unit on boost. 

 

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Pretty pleased with that. All we have to do now is enjoy the sweet smell of glue as we drift off into silent slumber tonight. 

 

 

 

 

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3 minutes ago, ToughButterCup said:

Excellent effort .

  @Onoff will promptly design the next version. But he'll never finish building it. @pocster will carry on where Clive left off. And build one out of glass. Free glass. 

 

Go away, I've escaped my DIY woes & the money pit and am busy:

 

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1 hour ago, Stones said:

Well done! I made my own silencer for the same reasons as you, and it has proved very effective. Didn't think of the multi holed baffles.  

 

Has it reduced air flow at all?

 I haven't checked. 

 

I was careful all along to make sure the sums of the openings added up to equal or greater the 160mm duct area out of the MVHR unit. In any case I doubt it. Flow is only really severely throttled at the terminals. 

 

 

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I am yet to build our acoustic silencer. We don't notice the MVHR on normal but do on boost. More is the cross room sound from the TV or people talking, so I'm think more on the lines of baffles at the ceiling terminals. Has anyone tried that?

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  • 1 month later...
  • 7 months later...
On 22/10/2021 at 08:54, joe90 said:

I too made my own silencer and combined it with the manifold, ply box lined with accoustic  foam.

I am just working up the design for my distribution and silencing system - do you have any more details of yours you can share - I think there was a post on e-build about it but that is long gone now.

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3 hours ago, MikeSharp01 said:

I am just working up the design for my distribution and silencing system - do you have any more details of yours you can share - I think there was a post on e-build about it but that is long gone now.

Just a ply box split in half, one side “input” the other “exhaust “. All flexi pipes siliconed into the box, the dampers are really “Heath Robinson “ Perspex discs mounted on dowels and a nail to turn and indicate position. Large pipes into MVHR as the pic. Box lined with sound absorbing foam with baffle to make the air go around the silencer before exiting, foam strip to seal lid when screwed on. 
 

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1 minute ago, joe90 said:

Just a ply box split in half, one side “input” the other “exhaust “. All flexi pipes siliconed into the box, the dampers are really “Heath Robinson “ Perspex discs mounted on dowels and a nail to turn and indicate position. Large pipes into MVHR as the pic. Box lined with sound absorbing foam with baffle to make the air go around the silencer before exiting, foam strip to seal lid when screwed on. 

Thanks Joe, that's very helpful, I was wondering how I was gong to make the dampers work for each of the outlets (inlets depending).

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2 minutes ago, MikeSharp01 said:

that's very helpful,

I also made my own terminals (cheap skate) but did the throttling at the manifold as some have said the terminals with throttles can make noise in the room, our Jeremy did the same thing 👍

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Interesting idea, it would help dampen the fan noise somewhat too.

 

In line with the passivhaus guidance you will only be able to add 10W/m2 of floor area before the air gets too hot and dust particles start to smell. 

 

With cooling, condensation from the radiator might be an issue. Cool project however. I'll follow with interest. 

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  • 7 months later...

Interests me whether hard surfaces between the foam in the first layer would be beneficial. Foam is used in sound studios to stop resonance and reflection on hard surfaces that are there to stop the transmission of sound through. If you think of a microphone, it has the foam on it to stop wind noise, not the transmission of sound. 

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Yes, I'll replace it with something like OSB soon I think. 

 

My logic was that there will be so much airflow through it that all small particles and off gassing will get done pretty quickly and become inert . 

 

 

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