Soundproofing
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Table of Contents
Quiet Shed - This article is part of a series.
Airtightness #
Sound travels readily through air, so airtightness is the first step in soundproofing.
I wrapped and taped the building as described on the cladding page.
And both the door and the opening window had airtight compression seals of thick rubber.
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The door seal made it very difficult to latch the door. So I added a big strong handle to pull it closed. I’m fine with this as I will be the only one using the workshop.
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Walls #
Soundproof construction generally relies on either high mass, or isolation between layers. Sound studios are often built with double walls - a box within a box. But some level of isolation can be achieved in a single wall by using staggered studs. This isolates the exterior cladding from the interior lining for most of the wall area - with the exception of the top and bottom plates.
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For acoustic insulation, soft flexible materials are preferable to rigid ones.
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Ceiling #
The ceiling was also insulated between the rafters.
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I did not do staggered stud construction in the ceiling. The rafters were all 90mm deep. Instead, I took another approach to isolation. Two layers of plasterboard, with acoustic glue between them.
The gold standard for this is a thing called Green Glue but it is too expensive for me. I went with Bostik Ultraset 3 in 1 (acoustic) flooring adhesive. Maybe it will do something. In any case, doubling up the plasterboard adds mass which helps.
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The second layer of plasterboard was assembled from offcuts.
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Floor #
I was particularly concerned with structure-borne noise. Such as my table saw directly vibrating the floor and through it the whole structure. To absorb that, I used a 4mm-thick rubber underlay, together with a 3mm layer of acoustic flooring glue.
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Vinyl tiles went on top of that as described on the finishing page. It certainly feels soft underfoot.
Door #
Since I made my own door, as described on the windows & door page, I stuffed it full of glasswool insulation (offcuts).
![](/posts/quiet-shed/5-soundproofing/door-insulation_hu059032a1066ed2295c963b78c76966ae_225440_660x0_resize_q75_box.jpg)
Also, as the face of the door is solid 17mm plywood, it is heavy. (I know, I just barely managed to carry it.) The mass will help with sound deadening also.
Windows #
It turns out that twin-wall polycarbonate is extremely bad acoustically. I should have known this, as when I go inside my greenhouse, it sounds just the same as being outside.
A single pane of 6mm acrylic is more or less the same as a single-glazed glass window, which is also not great.
So my windows were definitely the weak point in my soundproofing efforts. I decided to rectify that by putting up secondary glazing. Bring out the big guns: 10mm thick acrylic, with a huge 90mm airgap. I bought 4 sheets of 1220x610 for $356 from Acrylics Online. (The two triangular end windows could be cut out of a single sheet.)
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Because I had not designed for secondary panes, I had to build frames for them to be fastened to. These were about 20mm all around.
![](/posts/quiet-shed/5-soundproofing/secondary-dryfit_hua8339b15c9e7a7716dccc6af30d19335_107690_660x0_resize_q75_box.jpg)
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I drilled holes for 6mm diameter roofing screws (oversized to 8mm holes). Then I stuck rubber sealing strips around the frame, which would be compressed by the acrylic to form an airtight seal.
I also put some desiccant in the gap to avoid any condensation.
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See the performance page for soundproofing results.