Why We Don’t Sell “Soundproof” Curtains or “Noise Reducing” Curtains

The STC rating for most “soundproof” curtains is in the 20 STC range, maxing out around 26. This is far below the minimum of STC 40. It’s even lower than a double-pane window, with only an STC rating of 28-30.

The Sound Transmission Class (STC) rating system is a scientific rating system used to determine how much sound is blocked by components of building partitions, like walls, windows, exterior doors, curtains, etc. It’s generally accepted in the sound abatement industry that the minimum rating for soundproofing is STC 40. Anything below 40 does not reduce sound significantly.  Soundproof curtains are nearly half the required minimum STC rating of 40.

There are some simple reasons that curtains have a low rating. If you boil down the basic components of effective soundproofing products for windows, you find three main elements are addressed:
1. A tight seal around the opening in the wall where the window is installed.
2. A sufficient air gap between the window and the soundproofing product.
3. Sufficient mass-per-square-foot/meter of the soundproofing product.

Curtains have a sufficient air gap between the fabric and the window’s glass when installed correctly. But they don’t have any seal, nor do they have sufficient mass. Not having any seal means that noise goes around the curtain’s edges.  Not having sufficient mass (density) means that sound waves pass through the fabric.

In comparison, soundproof inserts made of laminated glass have all three elements when correctly installed – a tight seal, a sufficient air gap, and high mass (density). That’s why their STC ratings are in the high 40s (ours is STC 48), more than twice the rating of curtains. Even plastic (acrylic) inserts have a much higher rating than curtains, even though their mass is half that of laminated glass because they have a tight seal and a sufficient air gap when correctly installed.

For a good explanation of the Sound Transmission Class (STC) rating system, please visit https://en.wikipedia.org/wiki/Sound_transmission_class#:~:text=Sound%20Transmission%20Class%20(or%20STC,windows%20and%20exterior%20wall%20configurations.

Please remember: Any soundproofing product you are considering for your windows needs to have an STC rating of 40 or higher.