Can noise be reduced by 7 decibels with a curtain?

Question

I would like to reduce noise in my room and found a site selling curtains which can reduce noise by 7 decibels.

Is this kind of reduction really possible with just a curtain?

I wonder if this is not just a commercial argument to sell highly priced curtains.

Improving the level of acoustic comfort is only possible by increasing the weight and density of the material used. Based on this principle, Moondream developed a curtain which, through the successive juxtaposition of three components, achieves a significant noise reduction: up to 7 decibels* (on average).

This is made possible by combining 3 different fabric layers

• 1st component: 1 very heavy fabric with also acts as a blackout layer
• 2nd component: 1 external fabric made of equally heavy brushed cotton
• 3rd component: resting between the 2 other layers, a thermal insulation fabric

Source

Answer 1

They missed out one vital piece of information - at what frequencies?

They'd need to be made of lead to stop anything below 100Hz…

_{I wonder whether their mosquito-repellant curtains work when they're open too ;-)}

Answer 2

Very generally, foam/textile/mineral wool absorbs high to mid range, depending on the thickness of the material, while attenuating deeper frequencies requires serious mass. And don't forget the importance of an airtight seal. As long as air can move between spaces, so can sound.

Looking at the Moondream website, it seems the airtight seal needs to be provided by a double-glazed window. So far, so good. Naturally, adding mass or absorption in front of a barrier will help damp sound. I guess if you need curtains that damp sound, these might work. If you need to soundproof or treat a recording room - forget it.

Answer 3

We just hung up the Moondream curtains. We used them to cover an window opening in hopes of dampening the noise. We do not have an airtight seal and the curtains have made very little difference. I definitely would not call them "the best drapes against light, cold, heat, noise." They are a slightly heavier version of curtains you can get at Walmart. They are not a bad product, but I was hoping for something heavier and more effective. In the past, I've had a great experience using lined curtains from Walmart for extra thermal insulation, and I was hoping that a product that purported to be specifically designed to dampen noise would be at least as effective as the Walmart curtains were in retaining heat. The next thing I will try will be heavy velvet theater curtains.