A window that blocks noise and lets in air

Like many, I’ve been struggling to sleep in this hot and humid summer (which looks likely to break this weekend in the UK). I’ve slept with the window closed, only to awake drenched in sweat, I’ve tried opening the window, only to be disturbed by someone slamming a car door in my street. What I needed this summer was a window which simultaneously blocked sound while letting some air waft in.

Naturally ventilated schools and offices have solved this problem, but the structures they use would be too large to sensibly fit on the front of a normal home. Now two Korean researchers, Sang-Hoon Kima and Seong-Hyun Lee, have claimed to have designed a window 120mm thick which attenuates sound from 700 to 2200 Hz by 20 -35 dB. [1] This is about 5 dB worse than the performance of a standard 20mm thick double glazing unit.

As a sound wave tries to pass through the window, the air in the chambers sandwiched between the panes counteracts the sound’s movement. The cylinders you can see in the photo are there to force the sound to spread out (diffract) into the chambers. Each white cylinder is an air filter designed to stop the holes whistling in the wind. I’d be interested to see the performance of the device while the wind is blowing. Would air flow reduce performance?

The window that lets through air but blocks sound

The window that lets through air but blocks sound [1]

The window is an example of an acoustic metamaterial, a substance that is built up from small building blocks to have particular acoustic properties. While acoustic metamaterials are a popular area of research, I don’t know of any application where they are in day-to-day use. While the attenuation from the window is impressive, it will be more expensive to construct than a normal opening window, and cost might ultimately determine whether this technology becomes commonly used.

Notes

[1] Sang-Hoon Kim, Seong-Hyun Lee, “Air transparent soundproof window” http://arxiv.org/abs/1307.0301

2 responses to “A window that blocks noise and lets in air

  1. Pingback: A window that blocks noise and lets in air | ultrafonic

  2. Get some wax ear plugs. They block out about 95% of noise so you could still sleep with the window open but not hear all the noise the neighbours make. Coming from Sydney I know something about humidity!

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