Active Noise Cancellation for Automobiles

Imagine the inside of an automobile cabin without any roadway noise. For some drivers, being unable to hear the hum of tires on asphalt can be a disconcerting experience while, for others, it is as close as they can get to automotive paradise. The move towards noise cancelling technology is not new. Passive noise cancellation has long been an area of intense research by automotive engineers and specialists in the field of auto acoustics. This involves the use of dampening foams and other sound-absorbent materials to minimize engine and road noise inside the cabin. Active noise suppression, however, is a relatively newer technology that seeks to mitigate nearly all intrusive noise from the cabin.

One of the two key players in active noise cancellation technology is international automotive audio and connected systems giant Harman. The company’s HALOsonic Road Noise Cancelling (RNC) technology works on the principle of phase reversal of the noise and vibrations within the cabin. The system uses four microphones that are mounted inside the cabin to record ambient noise and four accelerometers on the car’s chassis that relay data to a central processing unit that generates a 180-degree reverse signal to cancel out the recorded noise, creating a quiet cabin environment that is free of humming without the addition of heavy passive noise cancellation materials. The key to Harman’s system is the pre-detection of high-frequency road noise through the accelerometers, enabling the system to create a suitable anti-noise wave.

American audio powerhouse Bose Corporation pioneered active noise cancellation over 30 years ago and has placed the entire gamut of its work in this area onto a single chip that can be installed into a car with the in-cabin acoustic hardware. However, research continues in the areas of mitigating the complex blend of frequencies that constitute road noise. Other operators such as Honda also continue to develop innovative ways.