Noise is everywhere, and it doesn’t seem like there is an escape from it.
Or is there?
Dr. Scott Sommerfeldt, dean of the College of Physics and Mathematical Sciences, and Mike Alder, of BYU Technology Transfer, discussed ongoing research in active noise control with Marcus Smith on The Morning Show on June 30.
Sommerfeldt’s research is focused on active noise control, which is one of several ways that is used to mitigate noise.
“Active noise control . . . is where you can cancel sound with sound, in layman’s terms,” Sommerfeldt said. “As the pressure goes up from noise, if you can create a pressure that goes down, they will cancel each other and make it quiet there.”
The way this works is through the sound waves. In order to cancel out the noise, the shape of the cancelling wave must be the exact opposite of the source wave. This can get tricky in situations where the noise needs to be cancelled everywhere or where there are multiple frequencies and multiple amplitudes, such as the recording studio where this interview took place.
“As your voice goes out, it actually has a different response at all the different points in this room,” Sommerfeldt said. “So if we’re going to cancel the noise in this room, we would have to match that spatial pattern at every point in the room.”
Cancelling unwanted noise in the room, though difficult, is feasible, but what about for the myriad of noises we may be exposed to outside, like the sound of cars on a highway? Cancelling unwanted noise from this myriad of sources seems vain, and Sommerfeldt agreed that it was. However, he said that, “. . . there are certain things where you can get impressive results as long as you can understand what the limitations are.”
Sommerfeldt has worked to cancel or attenuate sound all around the source of the noise so that no matter where a person stands, it’s quieter. One of the successful applications he’s had is with computer fans.
“We surround the fan with three or four small speakers. And then it’s all driven by what’s called a digital signal processor, essentially a computer chip, that can process all that information and figure out how to control those speakers in a way that it inhibits the creation of sound,” Sommerfeldt said.
For the best results, the object that’s being used to cancel the sound (like the speakers used with the computer fans) needs to be close to the source of the noise. This results in “coupling,” which is when the object and the sound source prevent each other from creating sound. Thus, global attenuation is achieved because “sound isn’t being created in the first place.”
This kind of technology could help with a wide range of problems, ranging from making a home theater room quieter and more enjoyable, to making car engines quieter, to changing occupational hazard conditions for those who work in noise-dense areas.
Mike Alder, of BYU’s Technology Transfer who helps market BYU innovations for commercial use, joined in on the discussion regarding the changes this technology could bring.
“[This is] exciting technology,” Alder said. “This technology is co-developed with the Caterpillar company. Under the dash [in a car] we could install a box and have in the roof an energy density probe, and then use the speakers in the car to cancel ambient noise. That’s possible with this technology. I am amazed.”
Technology with similar functions has found its way into the market in forms such as headphones that are worn on airplanes to reduce noise.
“Some things will always be very challenging to do, but there is progress that could be made there,” Sommerfeldt said. “This [technology] does have the potential to bring noise down considerably. It’s been a little slow in coming, but I think it’s starting to take hold.”
To listen to the entire episode of The Morning Show on BYU Radio, visit BYU Radio The Morning Show—Noise Mitigation.