It could be the answer to the dreams of those living in city centers. Researchers from South Korea have unveiled the "ultimate window," a windowthat blocks outside noise but allows air to pass through indoors.
Double- glazed windows have tiny holes that let air through, but prevent the most annoying frequencies from reaching the ears of the occupants.
The Sang-Hoon Kima and Seong-Hyun Leeb from Mokpo National Maritime University designed the air-transparent, soundproof window creating many «smart» isolated blocks. Each of these has dimensions 150x150x40 mm and in its center a hole of diameter 20 or 50 mm. The blocks function as reverberation chambers, with the sound waves bouncing inside them, canceling each other.
Experiments have shown that holes with a diameter of 20 mm are effective at suppressing noise across all frequencies, while holes with a diameter of 50 mm are more effective for noises in the 700-2200 Hz range. This tends to be the spectrum of artificial sounds, leaving natural sounds in the 0-500 Hz range largely undisturbed.
By sending 80 decibel sound waves – louder than a vacuum cleaner– through both windows, the researchers found that the holes reduced noise levels by 30-35 decibels (about the same as a quiet suburb).
The size difference in the size of each hole makes window coordination possible, meaning each separate block will be able to «block» sounds from a single frequency range and not from another.
«For example, if one lives in an area where there are low‑frequency sounds from the sea waves and noise from machines operating at high frequency, one will be able to hear only the sound of the sea» the researchers say, according to a publication by MailOnline.
Source: defencenet.gr
