Wireless signals outpace sound waves for better noise cancellation
Active noise-cancelling headphones work by generating a sound wave that is 180 degrees out of phase with the ambient noise. This requires the headphones to have a microphone inside the ear cup to listen for the noise to be cancelled, but this means the noise-cancelling circuitry doesn't have a lot of time to generate the anti-noise signal and some ambient noise will get through. By moving the microphone towards the noise and employing wireless technology, researchers have now developed better noise-cancelling technology that doesn't require bulky noise-blocking headphones.
The new technique developed at the University of Illinois' Coordinated Science Laboratory takes advantage of the fact that wireless signals travel a million times faster than sound waves. So, by placing the microphone closer to the source of the noise to be cancelled and sending the soundwaves to the earpiece wirelessly, there is more time to generate a better anti-noise signal.
"Our ear device gets the sound information in advance, and has much more time to produce a better anti-noise signal," says Romit Roy Choudhury, a professor at U of I's Dept. of Electrical and Computer Engineering (ECE).
Although such an approach would be difficult to make use of while walking down the street, the researchers give the example of an office environment, where someone in their office wanting to cancel out the chatter of workmates in the hallway outside could place an Internet of Things (IoT) microphone at the office door.
Because this approach results in more effective anti-noise signal, the researchers say it's possible to achieve a comparable level of noise cancellation as headphones with ear-encompassing ear cups using only a behind-the-ear device that doesn't completely block the ear canal. Additionally, it would be possible to achieve even better noise cancelling by using the technology in a conventional noise-cancelling headphone form factor.
And if the idea of sending audio signals around an office wirelessly over IoT networks raises security and privacy concerns, the researchers say that shouldn't be a problem because the microphone device is analog and, unlike common IoT devices such as Amazon Echo and Google Home, isn't capable of recording any sound. Sheng Shen, lead author of the study, says, "the moment the device hears the sound it is sent out wirelessly."
"This is bound to change the way we think of noise cancellation, where networks of IoT sensors coordinate to enable quieter and more comfortable environments," says ECE Assistant Professor Haitham Hassanieh, a co-author on the paper.
Said paper will be presented at the Association for Computing Machinery Special Interest Group on Data Communication (ACM SIGCOMM) Conference taking place in Budapest, Hungary, this month.
The video below gives an overview of the technology.
Source: University of Illinois