Scientists Say You Can Cancel the Noise But Keep Your Window Open

An anonymous reader quotes a report from The New York Times: Researchers in Singapore have developed an apparatus that can be placed in a window to reduce incoming sound by 10 decibels. The system was created by a team of scientists, including Masaharu Nishimura, who came up with the basic concept, and Bhan Lam, a researcher at Nanyang Technological University in Singapore. Their results were published on Thursday in Scientific Reports. The prototype is not yet the most practical device in real world conditions, but it points the way toward the development of technologies that may help ease the strain of noisy city living. Borrowing from the same technological principles used in noise-canceling headphones, the team expanded the concept to fit an entire room by placing 24 small speakers in a window. The speakers emit sound waves that correspond to the incoming racket and neutralize it — or, at least some of it. The system is based on the frequency of the sound waves and, for now, the optimal range is between 300 and 1,000 hertz. […] The system uses a microphone outside the window to detect the repeating sound waves of the offending noise source, which is registered by a computer controller. That in turn deciphers the proper wave frequency needed to neutralize the sound, which is transmitted to the array of speakers on the inside of the window frame. The speakers then emit the proper “anti” waves, which cancel out the incoming waves, and there you have it: near blissful silence. Unfortunately, there are some limitations. The system works best from the types of steady noise sources found within the optimal frequency range and isn’t great at neutralizing sporadic noises. Also, since human voices don’t fit within most of that range, they won’t be canceled out.