Jul 15, 2020 06:00:00

A device that reduces the noise coming in from the open window by half has appeared

In the hot season, it's tempting to open the windows to put cool breeze into the room, and

ventilation is encouraged as a countermeasure against the new coronavirus infection (COVID-19). However, there are also worries that if you open the window, the noise outside will enter the room. By installing the newly announced device inside the window, it is possible to reduce noise by half and achieve both ventilation and quietness in the room.

Active control of broadband sound through the open aperture of a full-sized domestic window | Scientific Reports
https://www.nature.com/articles/s41598-020-66563-z

Scientists Say You Can Cancel the Noise but Keep Your Window Open-The New York Times
https://www.nytimes.com/2020/07/11/science/windows-street-noise.html

Noise-cancelling windows halve traffic sounds even when they're open | New Scientist
https://www.newscientist.com/article/2248486-noise-cancelling-windows-halve-traffic-sounds-even-when-theyre-open/

This time, we developed a device that reduces noise by attaching it to the window, Bhan Lam who studies electronics at Nanyang Technological University in Singapore and Masaharu Nishimura of Tottori University Graduate School of Engineering. The research team. “I was born and raised in a small, noisy town, so I am motivated to solve the noise problem,” Lam from Singapore told the New York Times.

The following is a photo of the prototype of the 'Active Noise Control (ANC) system' created by Lam et al. for experiments. The ANC system consists of a sensor mounted on the outside of the window and 24 4.5 cm diameter micro speakers lined up inside.

When the sensor of the ANC system detects noise coming in from the outside of the window, 'anti-noise' in which the sound wave has the same frequency as the noise but in opposite phase is generated from the speaker, and the noise is canceled. It's a mechanism. Lam said, 'This is the same principle as the noise canceling earphones' about this principle.

When the research team actually installed an ANC system on the window of the experimental room and let noise flow from the outside of the window, the noise reaching the room was reduced by up to 10 decibels. When the sound drops by 10 decibels, most people feel that the volume is halved.

Below is a graph of the results of experiments conducted from the top left on white noise, highway noise, railway noise, and airplane noise.The vertical axis of each graph shows the loudness and the horizontal axis shows the frequency of the sound. I will. In addition, in the graph, the solid line represents “without ANC system/open window”, the broken line represents “with ANC system/open window”, and the dotted line represents “without ANC system/window closed”. In both graphs, the broken line is located just halfway between the solid line and the dotted line, and when using the ANC system, the noise level is about halfway between when the window is fully opened and when the window is closed. You can see.

The ANC system is capable of reducing the sound of 300 to 1000 hertz (Hz) that is often generated from cars and trains, and it continuously generates due to the nature of detecting and neutralizing the sound. It is suitable for reducing the sound being heard. Therefore, it is ideal for reducing the damage caused by traffic noise found in urban areas. On the other hand, it is said that it is not good at bass sounds below 300 Hz and the sounds of people with high voices talking.

The research team plans to carry out further experiments on the ANC system developed this time by conducting experiments in an actual environment rather than in the room created for experiments.