Finding a Better Way To Quiet Noisy Environments
|UCSD engineering professor Raymond de Callafon has developed an noise-reduction algorithm that more effectively eliminates unwanted sounds.|
“Noise cancellation is a hidden technology that most consumers aren’t aware of, but vehicles made by BMW, Mercedes, Honda, and other companies are now using it,” said Raymond de Callafon, co-author of the paper and a professor of mechanical and aerospace engineering at UCSD’s Jacobs School of Engineering. “Our new technique should greatly expand the potential of active noise-cancellation technologies.”
T his “feedforward” active-noise control can reduce unwanted helicopter and cabin noise or the steady roar of industrial air handling systems by 40 decibels or more. However, most commercial systems suffer from acoustic feedback because the anti-noise signal produced by the noise-cancellation speakers can feed back into the microphone and become amplified repeatedly until the resulting sound becomes an ear-splitting squeal or whistle.
“Most people ignore this acoustic coupling but we took it into account and designed the feedforward noise cancellation knowing that the acoustic coupling is there,” said de Callafon.
For example, the algorithm developed by de Callafon and Ph.D. candidate J. Zeng may be adapted to cancel unwanted complex signals that are moving, such as the sound of bustling urban traffic coming through a ventilation opening.
“We think we’ve developed a totally new approach that works by generating the ‘feedforward’ noise cancellation signals and adaptively changing them in the presence of acoustic coupling,” de Callafon said. “This has been a really complicated problem to solve and we think the approach we’ve taken will have a significant impact on the field.”
The research was supported by the William J. von Liebig Center for Entrepreneurism and Technology Advancement at UCSD.