AsianScientist (May 16, 2018) – A team of researchers at Nanyang Technological University, Singapore (NTU Singapore) has developed a device that can reduce noise pollution entering buildings.
In densely populated urban centers, noise pollution caused by machines and transportation systems can be a nuisance. Scientists at NTU Singapore have thus invented a device that could reduce noise by up to 50 percent.
The device uses ‘active noise control’ wtechnology, found in many high-end headphones, that is adapted to work in a large open area. The benefits of this invention are two-fold: windows can be left open for fresh air without disturbance from external noise pollution and the need for indoor air-conditioning is reduced.
“Compared to noise cancellation headphones, what we have achieved is far more technically challenging as we needed to control the noise in a large open area, instead of just around the ear,” said Professor Gan Woon Seng, director for NTU’s Center for Infocomm Technology (INFINITUS), who led the research.
Currently at the prototype stage, the device uses eight watts of power, similar to a small portable Bluetooth speaker. Several units are placed together to form a grid-like array on a window grille to reduce external noise.
The device uses a special sound-emitting mechanism which works like a speaker and is hooked up to a processing unit. Equipped with a microphone, it can detect noise even before it reaches the window and computes the attributes of the incoming noise in real time.
It quickly emits a countering sound, or ‘anti-noise,’ that has the same waveform characteristics of the invading noise but with one difference: it is inverted or ‘flipped.’ When both outside noise and anti-noise converge, they cancel each other out, resulting in a softer ambient sound entering living spaces.
“Our innovation not only computes the right amount and type of ‘anti-noise’ to emit, but also does it faster than the detected noise can reach inside the building,” explained Gan.
The research team conducted the tests using a soundproof chamber at the university’s labs. Various recorded sounds from construction sites, jet engines and trains were used as noise sources during the tests.
The researchers are working with government agencies in Singapore to further improve the technology to make it viable for commercial and residential applications.
“Ultimately, we aim to integrate this technology into window grilles that can help mitigate urban noise pollution conveniently,” said Gan.
The article can be found at Murao et al. (2017) Mixed-error Approach for Multi-channel Active Noise Control of Open Windows.
Source: Nanyang Technological University.
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