The breathing mode-shape 0: Is it the main acoustic issue in the PMSMs of today´s electric vehicles?

It is well-known that electric vehicles emit high-frequency acoustic noise, which can be prejudicial to market acceptance. It has often been reported on vibration mode-shape 0 of the electrical machine. However, this vibration shape has never been characterized as the main noise source of the electrical traction machine for a broad variety of cars throughout the market. This paper examines the acoustic behavior of four commercial cars by means of sound-pressure spectrograms, which were measured during test drives. It is shown that automotive electrical machines with a high number of pole pairs mainly suffer from mode-0 borne noise, which can dominate the overall acoustic performance of the vehicle.