Road Noise Cancellation (RNC)

Road Noise Cancellation (RNC)

Road Noise Cancellation (RNC) is an acoustic control technology engineered to actively suppress structure-borne noise generated by tyre-road interaction whilst driving. As a key branch of active noise cancellation (ANC) in the automotive field, RNC uses accelerometers deployed on the vehicle's suspension system to detect road vibrations in real time. A digital signal processor (DSP) then calculates and generates anti-phase sound waves, which are played through the in-car audio system to effectively neutralise low-frequency road boom entering the cabin. This technology is particularly vital for New Energy Vehicles (NEVs)—in the absence of engine noise to mask ambient sounds, road noise becomes significantly more pronounced in EV cabins, making RNC a benchmark feature for assessing smart cockpit acoustic refinement.

Core Technical Architecture and Operating Principle

The technical architecture of an RNC system comprises a vibration sensing module, a signal processing unit, and an in-car audio output system, establishing a complete closed loop from vibration detection to sound wave cancellation.

On the sensing front, accelerometers serve as the core detection hardware. The system features accelerometers installed on the suspension assemblies at all four wheel positions to continuously measure vibrations caused by uneven road surfaces. These vibrations are the root source of cabin road noise—as tyres roll over coarse tarmac, grooved concrete, or uneven terrain, vibrations travel through the suspension structure into the bodyshell, converting into low-frequency booming noise inside the cabin. The sensors capture vibration data in real time at millisecond intervals, providing accurate reference inputs for computing anti-phase acoustic waves.

The signal processing layer acts as the computational nerve centre. Vibration signals collected by the accelerometers are transmitted in real time to a processor (DSP or cockpit domain controller) running dedicated algorithms. Using adaptive filtering algorithms, the system swiftly calculates acoustic cancellation signals of identical amplitude but opposite phase to the target road noise. The algorithm requires high dynamic response capabilities to adapt parameters in real time across various road surfaces (such as coarse asphalt, concrete, or gravel). System latency is a decisive metric for noise cancellation performance—leading Chinese solutions have already reduced system latency to under 3 milliseconds. To achieve even more precise road noise management, some setups incorporate a feedback mechanism alongside traditional feedforward control: by utilising in-cabin voice microphones to monitor residual noise post-cancellation, the processor dynamically fine-tunes parameters for the next cycle of anti-phase sound waves, delivering a dual safeguard of rapid response and precise correction.

Finally, the processed anti-phase sound signals are played via the in-car audio speakers. The system typically engages the four door speakers and rear speakers to emit anti-phase acoustic waves, creating destructive spatial interference with incoming road noise to achieve effective noise reduction. Additionally, in-cabin microphones continuously track residual noise levels, allowing the system to adjust control signals on the fly based on road conditions and vehicle wear and tear.

Industry Trends and Localisation Breakthroughs

RNC technology is undergoing a paradigm shift from standalone hardware setups to software-integrated platforms. On the international stage, Bose unveiled its QuietComfort Road Noise Control technology at CES 2019, combining accelerometers, amplifiers, microphones, and the vehicle audio system to reduce noise, aiming for mass production by late 2021. Arkamys introduced a software-only RNC solution capable of delivering noise cancellation via existing in-car microphones and speakers without requiring extra DSPs or dedicated hardware, with scalability to support accelerometer-equipped premium configurations.

Chinese suppliers have achieved major breakthroughs in this segment. In 2024, Huayan Huisheng led the industry by rolling out China's first mass-produced RNC system integrated into a cockpit domain controller platform, breaking the technical monopoly held by international giants such as Harman and Bose. Its comprehensive performance represents a 30% improvement alongside a cost reduction of over 50% compared to international counterparts. The system is already fitted in production flagship models such as the ZEEKR 9X and ZEEKR 8X, with RNC installations exceeding 50,000 units in 2024—ranking first in the domestic market and among the top three globally. In 2025, Huayan Huisheng introduced its upgraded ERNC coupled noise reduction technology, achieving collaborative active suppression of both engine and road noise for the first time, capping in-cabin noise increase to within 0.5 dB when the range extender engages.

Driven by the rapid growth of the NEV market and rising consumer demand for cabin quietness, RNC is quickly trickling down from premium flagship models into the mainstream market. Adoption rates are projected to exceed 20% over the next three years, with total output value surpassing RM2,000,000,000. On the regulatory side, GB/T 46098—2025 "Performance Requirements and Test Methods for Automotive Active Noise Reduction Systems" was published in August 2025, establishing a standardised performance evaluation framework for RNC and related ANC systems. RNC is rapidly becoming an essential component of smart cockpit architecture and an indispensable feature in the drive towards upmarket automotive positioning.