Local active control of road noise inside a vehicle

The performance is investigated of a multichannel feedforward headrest system for the active control of interior road noise around a listener's ears in a vehicle cabin. An active headrest system is combined with the remote microphone technique so that direct measurement of the error signals at the listener's ears are not necessary. The formulation of the optimal observation filter for the remote microphone technique and the optimal controller for active control is presented in the time domain, to sense and control broadband random road noise. The estimation accuracy of the remote microphone technique is investigated through simulations, using the signals measured at a number of monitoring microphones and error microphones in the cabin of a large SUV. It is shown that disturbances at the virtual error microphones can be accurately estimated by a causal observation filter. The attenuation performance of the active headrest system using the remote microphone technique is also predicted offline, using measured plant responses, disturbance signals and reference signals, which shows that several peaks in the spectrum of the road noise can be reduced at frequencies of up to 1 kHz. The effects of delays and head movements on the attenuation performance are also studied. (C) 2018 Elsevier Ltd. All rights reserved.