Estimation of Interior Sound Quality in BEVs Regarding Measurements on the NVH Chassis Dynamometer: Focusing on Tonal Components

The NVH character of any car is highly dependent on its operating condition. With BEVs, it depends strongly on the driving speed, total torque, temperature and state of charge of the battery. For these reasons, OEMs usually want to measure many run-ups with constant torque steps or constant driving speed. The supposed simplification of the powertrain by the transition to electrified drive components and the elimination of auxiliary units poses new challenges for acoustic engineers. Unlike traditional vehicles with internal combustion engines, noise components of electric drivetrains fall into a range of audibility where the human ear reacts particularly sensitively. During a 3-year cooperation with a big OEM most of the premium BEVs on the German market were measured and benchmarked to get a feedback about their NVH performance. In addition, the desire for objective characteristic values arose. This paper introduces a Data-Driven Modeling approach for the estimation of sound quality from measurements on the NVH chassis dynamometer regarding tonality. Based on the extensive published research on the topic of prominence of tones in electric car interior noise and the new metric in the ECMA-74 standard, three premium BEVs of the SUV class were examined. In contrast to existing studies the entire operating range formed by engine torque and driving speed was included in the analysis. To determine the most relevant operating range for the buyer or driver, two European driving cycles (CADC and WLTC) were used and the necessary drive torque was estimated using a 1-dimensional vehicle model. The resulting visualization helps acoustics engineers to find the tonal phenomena more quickly and to make an initial assessment of development priorities. An approach for the structure borne noise is under investigation.