Written by:
The Engineering Challenge
Unwanted road noise inside the vehicle cabin has long challenged automotive engineers. Manufacturers have traditionally used passive treatments, including insulation, damping materials, and other countermeasures, to reduce it. However, these treatments add weight and cost and can be less effective at lower frequencies. In electric vehicles, added mass can also reduce vehicle range.
For NVH (noise, vibration, harshness) engineers, the challenge is to improve cabin refinement for vehicle occupants while balancing weight, cost, efficiency, and performance. Bose QuietControl Technology with Road Noise Control (RNC) gives engineers another tool for addressing that challenge.
Road Noise Enters the Cabin
The moment a vehicle’s tires hit the road, vibrations travel through the suspension, chassis, and vehicle body. Inside the cabin, this interaction can produce tire cavity resonances, cabin boom, transient impacts from uneven pavement, and other stochastic noises. In electric vehicles, the absence of engine noise can make this low-frequency road noise even more noticeable.
Â
An Active Approach to Road Noise Control
Traditionally, vehicle manufacturers have managed road noise with physical countermeasures that absorb broadband noise introduced from the road. RNC, as a digital NVH product, uses sensors, signal processing, and the vehicle’s audio system to reduce this unwanted noise inside the cabin. This active, software-based approach complements passive treatments, giving engineers greater control over low-frequency cabin noise.
Sensing, Prediction, and Control
Accelerometers mounted at multiple points on the vehicle detect road-induced vibrations early, before they become audible inside the vehicle cabin. The reference signals measured are then fed into the RNC algorithm, which allows it to predict the resulting low-frequency cabin noise. Using this prediction, a broadband feedforward control algorithm then generates an acoustically opposite cancellation signal that is played through the vehicle’s audio system to cancel the road noise at the occupants’ ears.
Prediction alone is not enough to deliver the most effective performance; road and tire conditions change over time. These conditions can change from minute to minute, requiring the system to adapt in real time. To address this, microphones are positioned inside the vehicle cabin to measure the residual noise after the initial cancellation. The algorithm compares the data from the accelerometers with the actual acoustic outcome measured by the microphones to continuously adapt the cancellation signal.
Together, these components create a closed loop adaptive control system that helps maintain stable and effective noise cancellation both during each drive and within the vehicle’s lifetime. But that is only part of the process; before the RNC system enters the market, NVH engineers must tune the vehicle to ensure the noise reduction can accurately address the noise that accompanies unique driving conditions.
Tuning RNC Under Real-World Conditions
To develop the tuning that delivers the intended noise cancellation, NVH engineers utilize Bose Automotive Tuning Suite (BATS). Both engineers at Bose and at the OEM utilize this tool to capture measurement data from vehicles within various driving conditions to simulate different cancellation signals. Engineers then apply the selected tuning configurations to vehicle hardware to test their effect on noise cancellation.
NVH engineers aim to reduce as much road noise as possible while keeping the system stable across all road conditions. A tuning that addresses noise in one driving scenario may not work for every drive; unique road vibrations, sensor anomalies, and in-cabin changes all affect how noise will be heard inside the cabin. BATS enables engineers to evaluate the balance between noise cancellation performance and system robustness, then select the tuning configuration that best meets the vehicle’s requirements.
By providing OEM engineers with access to the same tuning tools used by Bose, BATS gives OEMs the ability to manage RNC tuning themselves, with greater control and flexibility to achieve their desired noise cancellation performance. This helps OEMs create a quieter, more refined in-cabin experience for their customers.
The True Value of Road Noise Control
RNC gives NVH engineers a flexible, software-based tool to address road noise, tire cavity resonances, and cabin boom alongside physical treatments. It gives engineers another way to manage NVH trade-offs, helping them balance vehicle design priorities while supporting a comfortable, refined cabin experience.
For drivers and passengers, reducing constant, tiring noise allows occupants to focus more on music or conversation.
Beyond improving the cabin experience for occupants, RNC contributes to being an in cabin differentiator and helps OEMs balance weight, efficiency, cost, and overall vehicle performance.
As vehicles become increasingly software-defined, vehicle manufacturers are looking for smarter ways to manage these competing priorities. A software-based approach allows OEMs to address road noise without relying solely on traditional sound insulation materials, using software, algorithms, and computing power to deliver a capability that can be tuned, optimized, and continuously adapted to changing conditions throughout a vehicle’s lifetime. This provides greater flexibility and scalability across vehicle platforms and variants as the in-cabin experience becomes an increasingly important differentiator.
Interested in exterior vehicle sensing technology?
With a pass to InCabin, you’ll also get full access to our co-located sister event, AutoSens. Find out more here >>
