For city dwellers who usually have to choose between some peace and quiet in their urban oasis and a break from hot summer nights, a team of South Korean scientists have developed soundproof windows that block out noise, but not air.

That’s impossible, you say! But not for Sang-Hoon Kima at the Mokpo National Maritime University in South Korea and Seong-Hyun Lee at the Korea Institute of Machinery and Materials.

Kima and Lee managed to redesign soundproofing technology by adding a resonance chamber in which the resonant forces oppose compression, thereby creating a negative bulk modulus that attenuates any sound passing through it.

In layman’s terms, the windows are composed of two acrylic sheets, sliced into 150mmx150mm squares, with a 40mm-length “tunnel” drilled into the center. These squares are stacked on top of each other like building blocks, and the space between the sheets work as a resonance chamber that absorbs the energy of sound waves that pass through, without trapping the air between the sheets.

In lab tests, the acrylic windows reduced sound levels by 20-35 decibels over a sound range of 700 Hz to 2,200 Hz.

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