Noise cancellation technology is not news in vehicles, but the technology works best when the noise being cancelled is constant and predictable. Hyundai has now taken a step toward eliminating road noise, which is widely inconsistent.
The way noise cancellation (or Active Noise Control - ANC) works is that it takes a naturally-generated sound, captures the sound and within milliseconds plays it back in an inverted (or phase-shifted) format proportional to the original, effectively interfering with the original wave to reduce its volume (or even eliminate it). Because it’s a digital solution, ANC uses microphones and controllers that add much less weight than earlier solutions of insulation or thicker panels.
And because the original sound takes about four times longer to reach cabin occupants’ ears than the time it takes to cancel it, it’s an ideal system for sound control. But as effective as it is at cancelling constant sound from, say, the engine compartment, or predictable sound, such as windnoise, it doesn’t work well with unpredictable noises, such as those coming up through the floorboards.
That is going to become increasingly important as internal combustion engines are phased out and replaced with nearly silent electric powertrains, which means the drivetrain components are going to become the most prominent sound emitter and road noise won’t be camouflaged by engine noise.
The new Hyundai technology builds on ANC with Road Noise Active Noise Control (RANC), which is specifically designed to deaden the widely unpredictable sound waves coming from underneath the vehicle, as broken pavement is encountered, or tires react to surface imperfections.
“RANC is a remarkable technology which takes existing NVH technology to the next level,” said Gangdeok Lee, a Research Fellow of NVH Research Lab, “We will continue to take the leading position of NVH technology and deliver the highest level of quietness to customers.”
The RANC system can analyze various types of noise in real time (again using microphones) and produce the same type of inverted sound waves (using the Digital Signal Processor – DSP) to cancel them out, again within a couple milliseconds. And, it can do it separately for driver, front passenger and rear passenger positions, since occupants in those positions will experience the same sounds differently.
Tests have shown the system’s ability to cut cabin noise in half, to 3dB. And it sheds overall vehicle weight because all the road- and tire-noise insulation is currently being controlled using insulated panels or thicker metal panels.
The system took six years to develop, with the help of partners such as Korea Advanced Institute of Science and Technology, BurnYoung and audio company Harman, to name just a few. Hyundai has filed Korean and American patents for the core technology of the system — sensor locations and signal selection method.
The first application of RANC will be an upcoming Genesis model, though Hyundai didn’t give any indication as to what it might be.