Hyundai Develops the World's First Active Noise Cancelling Technology for Passenger Vehicles

author: Eric Walz   

Noise cancelling headphones are all the rage these days and are becoming a must-pack accessory for frequent fliers looking to get some work done or catch some sleep during a flight. For those traveling on the ground, autonomous electric vehicles may one day become a mobile workspace or a place to relax. However their near-silent electric powertrains can amplify road noise, making the passenger experience a bit less tranquil.

Hyundai Motor Group today announced it developed the world's first "noise cancelling system" that may be well-suited for electric vehicles. The automaker calls the system Road Noise Active Noise Control (RANC) and says it's the first-ever system that can dramatically reduces noise within the cabin of a vehicle.

RANC is a software-driven technology that analyzes the sounds inside the cabin to decrease engine and road noise, versus than the passive method of blocking noise through sound insulation placed under the hood and in the door panels and dashboards.

RANC builds on current Active Noise Control (ANC) technology, commonly found in noise-cancelling headphones. The system actively reduces noise by emitting soundwaves inverted to block incoming noise. 

Today, automakers looking to make the cabin quieter in vehicles typically add sound insulation materials and dynamic dampers throughout the vehicle, which not only increased weight but also failed to block the buzzing infrasound completely, which are frequencies lower than 20hz that cannot be blocked by insulation, Hyundai said.

Active noise cancelling technology (ANC) uses tiny lightweight microphones and controllers to control the noise and reduces infrasound, by  analyzing various types of noise in real-time and producing inverted soundwaves. The automaker said the technology is already available in some Hyundai vehicles. 

"RANC is a remarkable technology which takes existing NVH (noise,vibration, harshness) 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 system uses an acceleration sensor and calculates the vibration from the road to the car and the control computer analyzes road noise. The microphone continuously monitors the road noise cancelation status, and sends the information to the DSP. 

RANC is even able to conduct accurate noise analysis for each passenger, to reduce road noise for the driver, front passenger and rear seat occupants separately.

As its computation and signal transfer speeds are optimized, Hyundai says the system takes 0.002 second to analyze the noise and produce an inverted soundwave to counteract it, generated by the DSP (Digital Signal Processor). The inverted sound waves are sent to speakers via the vehicle's audio system.

Hyundai says that existing noise cancelling technology could only be utilized when noise is constant and the occurrence of the noise predictable, such as with the roar of a jet engine, which makes noise cancelling headphones so popular with air travelers. 

Vehicle interior noise primarily comes from three sources, vehicle powertrain noise, road noise, and wind noise. Since there is virtually no powertrain noise from electric and fuel cell electric vehicles, road and wind noise can become more audible for passengers. 

The RANC system can be fine-tuned for EVs

Hyundai's current ANC technology has been most commonly used to counteract constant noise from an internal combustion engine powered vehicle. However as more vehicles come with electric powertrains, the technology can be fine-tuned to block tire and driveline noise. 

Hyundai says the utilizing RANC can significantly reduce road noise and create a serene cabin for future electric and fuel cell electric vehicles.

There are different types of road noises that the new technology can process, including resonant sounds created between tires and wheels or rumble sounds coming up from an irregular road surface.

Hyundai tested the system in a variety of conditions, evaluating road surface, vehicle speed, and different seating positions to optimize the RANC to reduce in-cabin noise by 3dB, which is about a 50% decrease in noise compared vehicles without RANC. 

In addition to creating a quieter cabin or passengers, the system can potentially decrease the amount of unsprung weight in a vehicle, utilizing fewer insulating parts and dampers for noise reduction.

Hyundai said it invested six years of research and development for the mass production of RANC. The development phase involved a collaboration between industry and academia, with participation by Korea Advanced Institute of Science and Technology. The production version of the RANC system is built by Harman, a company best known for high-end audio products.

Hyundai has applied for domestic and American patents for the location of sensors and signal processing method, the core technology of RANC.

Hyundai said the new technology will debut in an upcoming Hyundai Genesis luxury sedan model. 

Eric Walz

Originally hailing from New Jersey, Eric is a automotive & technology reporter covering the high-tech industry here in Silicon Valley. He has over 15 years of automotive experience and a bachelors degree in computer science. These skills, combined with technical writing and news reporting, allows him to fully understand and identify new and innovative technologies in the auto industry and beyond. He has worked at Uber on self-driving cars and as a technical writer, helping people to understand and work with technology.