Noise-blocking Device holds Potential for Aviation Abatement

anti noise systemA grid of speakers facing outwards can play sounds that cancel out traffic noises
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Anti Noise Systems have been proposed before, but did not meet tests

Dr. Bhan Lam’s system of 20 speakers mounted on window-PROMISE

Impressive Publications, but no realistic test, YET

The idea of using noise cancelling technology to reduce the impact of aircraft is not novel. It has been proposed before but once the proposed system was put to practical tests, it did not reach expectations.

Dr. Bhan Lam[1], a research fellow with impressive credentials and a long list of accomplishments, has developed a system of speakers attached to the window that claims to reduce the sound level by 50% inside rooms, even with windows open. Great promise and even the proponents recognize that testing remains a major proof of concept, but the idea has received positive reviews in technical and general publications like Scientific American, Scientific Report, American Association for the Advancement of  Science, Smart2Zero,Futurism, the Daily Mail and even The New York Times!!!

Speaker System Blocks City Noise

Active control of broadband sound through the open aperture of a full-sized domestic window

Noise cancelling device by NTU scientists halves noise pollution through open windows

Open-window noise canceling system cuts outside sounds

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Noise-cancelling windows halve traffic sounds even when they’re open

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Scientists say you can cancel the Noise but keep your Windows Open

Noise-cancelling windows halve traffic sounds even when they’re open

noise cancelling window


 

TECHNOLOGY 9 July 2020

By Donna Lu

 

A grid of speakers facing outwards can play sounds that cancel out traffic noises

Danil Roudenko / Alamy

comparison with & without system

People living in cities with warm climates face a problem during summer months: keeping windows open for ventilation means letting in traffic sounds. A noise-cancelling device could solve this dilemma.

Bhan Lam at the Nanyang Technological University in Singapore and his colleagues have created a device that can halve NTU and Dr. Lamthe noisiness of urban traffic, reducing the sound coming through an open window by up to 10 decibels.

design and picture

To cancel out road noise, the researchers used 24 small loudspeakers and fixed these to the security grilles of a typical window in Singapore in an 8×3 grid. These grilles are a common feature across South-East Asia, says Lam. He adds that the spacing of the speakers was dependent on the frequency of the noise that they wanted to cancel out.

FAA LDN chart of typical noise

The team placed the window in a replica room and played road traffic, train and aircraft noise from another loudspeaker 2 metres away. The frequency of most of the noise from traffic and passing aircraft ranges from 200 to 1000 hertz. Large trucks and motorcycles tend to generate sounds on the lower end of the range, while the majority of the sound from motorways is around 1000 Hz.

The researchers spaced each speaker 12.5 centimetres apart facing outwards and programmed them to emit sounds at the same frequency of noise detected by a sensor placed outside the window.

aircraft noise in Hertz

The device was most successful at cancelling noise between frequencies of 300 and 1000 Hz, with up to a 50 per cent reduction in loudness for sounds within this range. It isn’t optimised for the noise from human voices, which have higher frequencies.

The effect is similar to the technology used in noise-cancelling headphones, which are often tuned specifically to cancel out the hum of aircraft engines, says Lam.

noise cancelling headset

The speakers the team used were only 4.5 centimetres in diameter – too small to cancel out noise at frequencies below 300 Hz. “A speaker needs to move a huge volume of air for low frequency sounds,” says Lam.

Having larger speakers is a possibility, but risks blocking out too much of the view from a window. The team plans to test a prototype in real-world experiments.noise abatement

 

 

 

 

 

 


Tune in for the real-world experiments of the system.!!!

the system graphic

[1] Lam Bhan received B.Eng. (Hons) and Ph.D. degrees in electrical and electronic engineering from Nanyang Technological University, Singapore, in 2013 and 2019, respectively, where he is currently a Research Fellow with the School of Electrical and Electronic Engineering. His current research interests include the acoustics of active noise control, soundscape, and signal processing for active control (Based on document published on 5 May 2020).



 

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