Active noise control in a luxury vehicle

Structure-borne road noise is a critical sound attribute for the overall Noise Vibration& Harshness (NVH) performance of modern luxury vehicles. Currentpassive NVH solutions require structural design modifications, in order to controllow frequency sources that cause structure-borne noise. Active Road NoiseControl (ARNC) has been demonstrated to several commercial vehicles as analternative solution that does not compromise other performances of the car,especially vehicle dynamics. Automotive manufacturers of luxury vehicles, suchas Bentley Motors Limited, are expected to build cars that meet high standardsof driving performance and refinement levels. This thesis focuses on the developmentof an active sound technology for road noise with the use of NVHanalysis methods, which are a common practice in the vehicle development process.Modern NVH methods of road noise analysis reveal the locations of themost predominant structure-borne noise sources. There are significant advantagesin using NVH analysis techniques for the design of ARNC systems, sincethey o_er integrated solutions to the automotive industry in terms of time andcost reduction. A method for defining the accelerometer sensors number andtheir locations on the axles has been developed as an alternative to existingmethodologies, which are applied from the early stages of the NVH development.A physical road noise simulator was developed for replicating road noise.Four random uncorrelated forces were applied on the tyres for analysing andevaluating ARNC systems. In terms of feedforward control, a computer modelof a causal adaptive feedforward system was used to investigate the relationshipbetween the locations, DoF and the performance of the control system.An adaptive system was installed on a Bentley vehicle for conducting the ARNCmeasurements. The adaptive ARNC system was tested on the physical road noisesimulator. The vehicle's tyres were excited by broadband random forces andmaximum 10 dB(A) reduction at the centre frequency of the tyre cavity resonancewas achieved. When the control was focused on the road rumble, then overall3 dB(A) up to 500 Hz were removed from the noise levels measured at the rearheadrests. In terms of road noise testing, a portable multichannel controller wasintegrated with the vehicle electrical system for road noise data acquisition andreal-time ARNC. Finally, the performance of the portable controller is predictedbased on data acquired by the same multichannel system and therefore highlightthe potential use of this system as an ARNC controller