Vehicle interior noise and vibration prediction by combination analyses of Component and Operational TPA

In this study, we propose an analytical method consisting of Operational TPA (OTPA) and Component TPA (CTPA) to predict the vehicle interior noise and vibration without the vehicle operational test in case the noise source such as engine was modified. In the proposed method, the blocked force of the noise source was obtained at a test bench and the vibration at the source attachment point on the vehicle was calculated by CTPA. After then, the response point signal (interior noise / vibration) is estimated from several reference point signals including the calculated vibration by OTPA. For the verification of this method, a simple vehicle model which is composed of four tires and a motor was prepared in addition to a test bench. OTPA was firstly applied to the vehicle model to analyze the contribution from tires and a motor to the body vibration (response point). The blocked force of a modified motor was obtained by CTPA at the test bench and the force was used to predict the response point by OTPA. Finally, the estimated interior vibration was compared with the actual measured response point vibration when the motor was replaced on the vehicle model and the accuracy was verified.

Warning Effect Evaluation and Control for Vehicle Turn Signal Sound

The sound quality of a turn signal sound is directly related to the driving safety and influences comfort during driving. A turn signal sound and interior noise always exist simultaneously while driving. However, none of the studies are performed to observe and control the change of a turn signal sound when the vehicle interior noise was changed. Therefore, this paper develops a method to evaluate and control the warning effect of a turn signal sound masked by vehicle interior noise. First, the turn signal sound and the vehicle interior noise at different speeds are measured and the time-frequency characteristics of the turn signal sound is analyzed. Second, the pairwise comparison method is applied to subjectively evaluate the warning effect of the sounds and the warning effect of the turn signal sound at 6~speeds relative to that at 40~km/h was obtained. Third, a new hearing threshold evaluating the warning effect is developed and used as a sound metric. This metric is employed to evaluate objectively the warning effect of warning sounds at different speeds. The subjective evaluation results are consistent with the objective evaluation results, which confirms the validity of objective evaluation. To keep the warning effect of the warning sound during the driving, two methods of controlling the turn signal sound are proposed and will be researched further in the future.

Case study: Separating source contributions of vehicle interior noise by operational transfer path analysis

The perception of vehicle interior noise is a key quality index to customers and automakers alike. By tracing noise back to key noise sources and paths, one can focus their refinement efforts. Aiming at the most efficient way to identify the primary noise sources in a vehicle cabin, this article establishes a framework of operational transfer path analysis (OTPA) for separating contributions of noise sources by operational measurements only. OTPA model design, measuring essentials and synthesis method used for separating vehicle interior noise contributions from the powertrain, tires andwindwere described in detail. To comprehend the implementation of OTPA on noise source separation, this article also addresses an exemplification study on an electric vehicle. In the case study illustrated, both spectral map and order extractions were used to validate if the OTPA synthesized results of the powertrain noise contribution agreed with the measured results. Tire noise contribution was validated using the tires driven by the dynamometer along with all other systems switched off. With well-validated OTPA model for the powertrain and tires, further individual path breakdown of the powertrain and tire noise then was investigated to identify key contributors to the interior noise. After clearly separating interior noise contributions, one therefore could design effective countermeasures to mitigate the dominant noise sources. With appropriate scheme of measurement and synthesis, the OTPA technique could therefore effectively serve target setting and refinement focus at foremost noise contributors.