A recent study has shown that a device that works similarly to noise-canceling headphones can help reduce the noise from outside when you open a window.
The new invention consists of 24 speakers, each 4.5cm wide, fixed to the grid layout on bars mounted inside a window, combined with a microphone mounted outside the window. If the microphone detects noise from outside the house, the speakers inside will immediately emit “anti-noise” – that is, sound waves with a reverse wave pattern compared to outside noise. This noise cancellation eliminates incoming sound, reducing the volume of noise pollution entering your home, even when the windows are open.
To test the device, the researchers placed it into a two-square-meter sliding window and opened the noise of streets, trains, and planes from a loudspeaker located 2 meters away. Using 18 in-room microphones, they discovered that the device had reduced the volume of noise at frequencies above 500Hz – which was the range including traffic and train noise – by almost half. This result is superior to the sound insulation of a single-winged glass window when closed.
The researchers note that their equipment is less effective against lower frequency sounds, such as noise from airplanes or power transformers. These types of sounds have a larger wavelength, and to eliminate them requires larger speakers that, if used, will cause visibility and airflow through the window to be blocked, accidentally Corrupted original purpose of the device. Active noise control is also less effective for frequencies higher than 1,000 Hz, which is a range of sounds including birds and human voices.
Window-mounted noise cancellation system
However, a previous medical study showed that halving noise pollution by half reduced the health risks caused by noise by 7-17%. Noise-canceling devices can be fitted to window bars, which are common in Southeast Asia.
“We hope this active noise control system will encourage the utilization of natural ventilation functions without having to worry about increasing noise pollution in cities.“- study author, Bhan Lam, a sound engineer at Nanyang Technological University in Singapore.
The device has now been optimized for sounds with properties that haven’t changed too much over time. It can be effective against noise that is less predictable, like machinery on a construction site, although Lam says it will require more complex handling.
Researchers are now planning to test their devices in real-world contexts.