Hyundai Motor Group develops active road noise control system
Hyundai Motor Group announced it has developed what it claims is the world’s first road noise active noise control (RANC) system. The system is designed to dramatically reduce noise within the cabin of a vehicle.
RANC builds on the group’s current active noise control (ANC) technology, which actively reduces noise by emitting soundwaves inverted to incoming noise. ANC is a software-driven technology that analyzes the in-cabin sound to decrease engine and road noise, compared to the passive method of blocking noise through sound insulation.
The existing noise insulation method involved sound insulations and dynamic dampers, which not only increased weight but also failed to block the buzzing infrasound completely. In contrast, ANC uses much lighter parts like microphones and controllers to control the noise and reduces infrasound more efficiently. The technology is already available in some Hyundai Motor Group vehicles.
However, due to the limitations of noise measurement and analysis technology, the existing ANC was only able to be used when noise was constant and the occurrence of the noise predictable. The group’s current ANC technology has been most commonly used to counteract constant engine noise. Given that it takes only about 0.009 second for road or engine noise to reach the passenger, the current technology was limited.
With RANC technology, Hyundai Motor Group says it is able to greatly improve in-cabin quietness. The new system can analyze various types of noise in real time and produce inverted soundwaves. The new technology can process different types of road noises, such as resonant sounds created between tires and wheels or rumble sounds coming up from the road.
The RANC technology employs an acceleration sensor and calculates the vibration from the road to the car; the control computer analyzes road noise. As the computation and signal transfer speeds are optimized, the company says it only takes 0.002 second to analyze the noise and produce an inverted soundwave, generated by the digital signal processor (DSP). The microphone constantly monitors the road noise cancelation status and sends the information to the DSP. RANC is able to conduct accurate noise analysis and rapid computation to combat road noise for the driver’s seat, the passenger seat, and rear seats separately.
Based on tests evaluating road surface, vehicle speed, and different seating positions, RANC was able to reduce in-cabin noise by 3 dB, which is roughly half the noise level without RANC. The group says that the system can potentially decrease the amount of unsprung weight in a vehicle, using fewer sound-insulating parts and dampers than before.
Hyundai Motor Group spent six years of research and development for the mass production of RANC. The pre-production phase involved an open innovation between industry and academia, with participation by Korea Advanced Institute of Science and Technology, WeAcom, ARE, BurnYoung, and others. The mass production phase was carried out with Harman to increase the competition.
Hyundai Motor Group has completed domestic and American patent applications concerning the location of sensors and signal selection method, the core technology of RANC.
The company says that, in the future, in-cabin quietness will become more important as internal combustion vehicles are phased out. Vehicle interior noise primarily comes from three sources: vehicle powertrain noise, road noise, and wind noise. Electric and fuel-cell electric vehicles have almost no powertrain noise, so eliminating road and wind noise "becomes even more imperative." Using RANC could significantly reduce road noise and create a quieter cabin for future electric and fuel cell electric vehicles.