Noise Cancelling Technology

For millions of people who live in large cities, there is a definite trade-off between opening their windows to enjoy fresh air and having to listen to the constant noise of traffic, jackhammers and sirens. But researchers in Singapore have developed a system that acts like a pair of giant noise-cancelling headphones to quiet an entire apartment.

It consists of an array of 24 small speakers that reduce incoming noise by up to 10 decibels. (It’s worth noting here that, since the decibel scale is logarithmic, every ten decibels represents an intensity level of ten times.) A microphone outside the window detects repetitive sound waves and determines the proper frequency needed to neutralize them. The speakers then emit “anti” waves to cancel them out.

Currently, the system is optimized to handle sounds between 300 and 1000 Hertz. That means that human voices are not filtered as well as things like traffic, trains, jets and construction equipment. It’s also not good at handling sporadic noises like firecrackers and car horns. Balancing the size of the speakers with the aesthetics of the system, as well as how much it blocks ventilation, is a next step in the design process.