Application of Noise Path Analysis Technique to Transient Excitation

Road induced interior noise, vibration and harshness (NVH) of a vehicle are greatly influenced by the design of the vehicle chassis and body systems. The strategy of improving vehicle NVH performance is to reduce vehicle body sensitivities to suspension force inputs and to increase the isolation of the chassis system to road irregularities. The effectiveness of the isolation is evaluated by the magnitude of transmitted forces at all suspension-body attachments. Currently, no technique is available to directly measure the forces over a broad frequency range. Many efforts have been made to develop force estimation methods, such as Noise Path Analysis (NPA) techniques. NPA techniques have been used to estimate the transmitted forces for steady-state road and powertrain excitations. This paper presents an ongoing effort to extend the NPA techniques to transient excitations, such as impacts caused by tar strips and pot holes. Rubber-strips were used to simulate bump excitations to a vehicle. Major noise paths to vehicle interior responses were identified, using the NPA inverse matrix method. This study can be used to assess the effectiveness of suspension isolation, and to provide design guidelines for impact harshness improvement.