Now that summer is upon us again, once in a while nothing beats a fresh breeze through an open window. However, the noise from the street can be quite distracting in the process. Inspired by the soundproofing technology also used in headphones, researchers from Singapore's Nanyang Technological University developed a system that can actively reduce disturbing noise from outside.
Noise-cancelling systems do not block sound but actively combat it with their own sound waves. Such systems use a microphone to listen to the incoming sound. Algorithms analyse this sound and generate an opposite version of it that is 'broadcast' through loudspeakers. When the two sounds converge, ambient noise from outside, for example in the form of honking cars or noise from the construction site, is muted.
This active noise-cancelling technology is widely used in headphones, headsets, helmets, cars and even anti-snoring products. Singapore-based scientists now want to use it on windows as well. The prototype of this is now a reality. It is made up of a network of small devices with microphone, speaker and processing unit. When fitted over a window grille, sound can be recognised before it reaches the window and processed in real time. The big challenge here is the large open space in which the sound has to be controlled. The prototype not only calculates the right amount and type of anti-noise, but also transmits it before the sound can enter the building.
The system was tested in a replica of a room, complete with doors and windows, within a soundproofed area. The sounds of construction site or passing planes, trains and cars were then simulated. According to the researchers, noise from these is suppressed by up to 50 per cent. Only downside to the current prototype: the noise may be less, but the bulky installation increases 'visual pollution' considerably. Consequently, efforts are now under way to further miniaturisation.
The video below demonstrates the noise-cancelling system.
