Virtual Reference Signals for Active Road Noise Cancellation in a Vehicle Cabin

When listening to music in a moving car, there are many noise sources that degrade sound fidelity. Active noise cancellation technology is one answer to reducing these distracting noises. In the domestic Japanese market, a system is now available that reduces engine induced resonance in the vehicle cabin. However, engine boom is just one noise source and its cancellation is not a complete solution. In this paper we describe an active road noise cancellation system.

To optimize cancellation of road noise in a vehicle cabin, it is very important to find reference signals that are coherent with the noise in the cabin. To meet this requirement, many accelerometers are needed to detect the vibration in the vehicle's suspension system. When analyzing those accelerometer signals, we find that in most cases, those signals over determine the noise sources. At Inter-noise 94 in Yokohama we proposed a new method to calculate orthogonal virtual noise sources from those over determined accelerometer signals^[1]. In this paper, we provide and discuss the results and method to implement a virtual reference signal that can be used for an LMS based active noise cancellation system.