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Noise-canceling windows soften the sounds of the city

The noise-canceling windows may be bulky, but they do a decent job of cutting external noise pollution
The noise-canceling windows may be bulky, but they do a decent job of cutting external noise pollution
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The prototype active noise-canceling window system is made up of a grid of devices that each contain a microphone, a speaker and a processing unit
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The prototype active noise-canceling window system is made up of a grid of devices that each contain a microphone, a speaker and a processing unit
The noise-canceling windows may be bulky, but they do a decent job of cutting external noise pollution
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The noise-canceling windows may be bulky, but they do a decent job of cutting external noise pollution
An infographic describing how the noise-canceling windows work
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An infographic describing how the noise-canceling windows work

Sometimes there's nothing like a nice breeze from an open window, but in the city that can come with an unwanted side order of street noise. Inspired by the kind of noise-canceling tech used in headphones, researchers at Nanyang Technological University, Singapore (NTU) have developed a window-based system that can actively cut noise coming from outside.

Noise-canceling systems don't just block sound, they actively counter it with their own sound waves. These devices use a microphone to listen to incoming noise, before algorithms analyze the waveform and generate an inverted version that is then emitted through speakers. When the two sounds converge, the ambient noise from outside is dulled, saving the listener from the honks of traffic or the endless hammering of construction sites.

This kind of active noise-canceling technology is already widely used in headphones, ear plugs, motorbike helmets, cars, and even anti-snoring devices. Now, the NTU team is aiming to stick it in windows too.

The prototype active noise-canceling window system is made up of a grid of devices that each contain a microphone, a speaker and a processing unit
The prototype active noise-canceling window system is made up of a grid of devices that each contain a microphone, a speaker and a processing unit

The prototype system is made up of a grid of devices that each contain a microphone, a speaker and a processing unit. Fitting over a window grille, this active array is able to detect noise before it reaches the window, and process the sound in real-time.

"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," says Gan Woon Seng, lead researcher on the project. "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."

To test the system, the team built a replica room, complete with windows and doors, inside a soundproof chamber. The prototype was attached to the window, and to emulate outside noise, a speaker was set up to play recorded sounds like construction work and passing planes, trains and automobiles. The researchers say it managed to reduce the noise by up to 50 percent.

An infographic describing how the noise-canceling windows work
An infographic describing how the noise-canceling windows work

Although the system cuts back on noise pollution, in its current form it adds a fair bit of "visual" pollution to your window. The researchers say that reducing the bulk is one goal of further work, as well as improving cost and noise-canceling efficiency.

"We are currently finding ways to improve the technology further so that it can be used not only at window grilles with large openings, but also provide a cost-effective solution that can be easily installed and replaced," says Gan. "Ultimately, we aim to integrate this technology into window grilles that can help mitigate urban noise pollution conveniently."

The researchers demonstrate the device in the video below.

Source: Nanyang Technological University, Singapore

Noise reduction device by NTU Singapore

3 comments
FabianLamaestra
This was already done years Ago by SolidDrive, installing noise-cancellation Transducers on the glass walls of boardrooms. This can be easily installed into the large window of a home to cancel out external noises. http://soliddrive.mseaudio.com
EcoLogical
I use a 'low-tech' solution to minimize noise through my window. Find (or build) a box that fits in the window. I have a sliding window so I put the flap (on the open end of the box) between the partially open window and outside screen. But first I cut a hole in one side (which became the bottom) of the box for airflow. I tried putting the hole on top but found that the bottom is best since some sound will deflect through the hole but most of it will be absorbed by the carpet.
KungfuSteve
Heres an idea... If Windows are desired to be opened, it tends to mean that its too hot inside. As such, maybe it best to combine sound nullification, with natural cooling. Such as a sort of water-fall... or dripping water based system. The water flow could potentially be altered based on the Audio Microphone(s) (which should probably be more like a few long ribbons, and magnetic sensory of the entire ribbon(s) )... Maybe easiest to envision as being somewhat similar in nature to those water based displays... that scroll text / images. The water may could flow down slightly overlapping + angled, vertical slats, similar to vertical blinds. If these were opaque, that could also double as a means to limit light, as well as airflow. If the water is made to partially spray off the surface into a fine mist... it could make a decent evaporative cooling effect. Also, any dust / pollution, could get caught in the waterflow... and captured in a replaceable / cleanable filter.