These New Windows Let the Summer Breeze In, But Block the Street Noise

A window speckled with little holes will let the air through, but not the sound

If you live in a dense urban neighborhood—the heart of Brooklyn, say—deciding to open your window is a complicated process. Getting some air flow would be nice, and the smell of grilled chicken from the food cart down the street is pleasant enough. But there are just so many people. And horns. And sirens. If only there were a way to get the air without the noise, so you can cool off without having your thoughts drowned out or your sleep interrupted.

Two Korean researchers, Sang-Hoon Kim and Seong-Hyun Lee, may have just the thing: they’ve designed a new kind of window that blocks the sound, but not the air.

Ok, but…sound waves are carried by air. So…wait, what? We know, it’s confusing.

The trick, says MIT’s Technology Review, comes from a clever design strategy that let the window effectively damp the sound out of the air before it passes through.

To make their soundproof window, the scientists took two sheets of plastic and drilled tiny little holes in them. As the air passes through the holes the sound waves get diffracted.

When sound waves pass through a narrow opening they get diffracted. Photo: Wikimedia Commons

But if this was all they did, say the researchers, your windows would sing “like a wind instrument.” So from here, once the sound waves are diffracted, they bounce around in a little chamber, sandwiched between the two pieces of plastic. Inside these little chambers, they say, the sound waves are attenuated. By hooking a few of these little chambers up in a row, each with a different sized hole to let the air through, the windows can strip different frequency bands of the sound from the air.

The sound-attenuating windows don’t look like much, but prototypes never do. Photo: Kim and Lee

The windows, the scientists write in their study, cut the sound by around 30 decibels, enough to turn a motorcycle into a quiet office. But, the little holes still let the air flow through. According to the scientists,

The structure of the air transparent soundproof window or wall is so simple that any carpenter can make it. The soundproof frequency range is tunable. There is a wide range of application areas such as soundproof windows of houses close to noisy area, the soundproof walls in residential areas, etc. For example, if we are in a combined area of sounds from sea waves of low frequency and noises from machine operating at a high frequency, we can hear only the sounds from sea waves with fresh air. These principles should work in water as well as in air and may contribute to underwater noise reduction for marine life.

Not to get greedy, but can they add a function that filters smell as well? Because while the chicken grill smells nice, the garbage rotting on the sidewalk does not.

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