To soundproof a window you need to add mass, seal air gaps, and ideally create a trapped air space, because a single pane of glass is thin, light and a major weak point for sound. The most effective DIY solution is a removable window plug; the most permanent is secondary glazing. Both beat any stick-on product.
Like all isolation work, this is soundproofing, not acoustic treatment. It stops sound passing through the window rather than improving how the room sounds. It fits into the wider plan in how to soundproof a home studio.
Why windows leak sound
Glass is dense but thin, so a single pane has limited mass and resonates easily. Older windows also have gaps in the frame and seals. Two panes very close together (standard double glazing) help with insulation but share resonances, so they are not as effective acoustically as panes with a larger air gap. Sound also sneaks through any unsealed crack.
Option 1: Build a removable window plug (best DIY)
A window plug is a dense panel that fits snugly into the window reveal and presses against the frame. A common build:
- A rigid backing board (such as plywood or MDF) cut to fit the reveal.
- A layer of mass loaded vinyl bonded on for added limp mass; see what is mass loaded vinyl.
- A layer of mineral wool (Rockwool) on the room-facing side to absorb some energy and help it seal.
- A compression seal around the edges so it presses tight, plus a handle to remove it.
The plug is removable, so you keep your daylight when you are not recording. It is one of the highest-impact, lowest-cost steps you can take.
Option 2: Secondary glazing
Secondary glazing adds a second pane of glass on the room side, with a generous air gap (the larger the gap, the better the low-frequency performance). Using a thicker pane than the original, and a wide gap, gives a real improvement. This is more permanent, lets light through, and is a strong choice if you cannot block the window entirely.
Option 3: Seal and add curtains
- Seal the gaps: acoustic caulk and weatherstripping around the frame close the easy leaks. Always do this regardless of other steps.
- Heavy curtains: dense, layered curtains reduce some high-frequency leakage and reflections, but they are a minor supplement, not a real barrier. Do not expect them to block bass.
What does not work
Stick-on foam, bubble wrap and thin films do little to block sound; they lack mass. Believing they will is another of the common acoustic treatment myths. Mass, air gaps and sealing are what move the needle.
Frequently asked questions
What is the best DIY way to soundproof a window?
A removable, well-sealed window plug made from a rigid board with added mass (such as mass loaded vinyl) and an edge seal. It is cheap, effective, and you can take it out to restore daylight.
Will heavy curtains soundproof a window?
Not really. Dense curtains help a little with high frequencies and reflections, but they have nowhere near enough mass to block meaningful sound, especially bass. Treat them as a supplement.
Is double glazing enough to soundproof a window?
Standard double glazing helps but is optimised for thermal insulation, with panes too close to perform well acoustically. Secondary glazing with a larger air gap, or a window plug, does more for sound.
