Used tyres could make EVs quieter

Although electric vehicles are significantly quieter than combustion-engine cars, they can still generate noises such as humming sounds that some occupants perceive as unpleasant. Researchers at Otto von Guericke University Magdeburg have now developed a new method of reducing noise from EV power electronics using material derived from recycled tyres.

Uni magdeburg altreifen recycling partikel daempfung geraeusche leistungselektronik — Foto: Jana Dünnhaupt/Uni Magdeburg

Electric vehicles generate sound from a range of sources, including tyre-road interaction, aerodynamic effects and onboard electronics. Researchers at the Institute for Engineering of Products and Systems at Otto von Guericke University Magdeburg have focused on the latter. Power electronics, inverters and other vehicle components can produce high-frequency noises such as whirring, humming or high-pitched whistling sounds. These noises are typically caused by vibrations and oscillations.

To reduce these noises, manufacturers have so far relied mainly on insulation mats. However, these components are comparatively expensive and add weight, which can reduce drivetrain efficiency. Prof. Hermann Rottengruber and his research associate Dr-Ing. Braj Bhushan Prasad therefore investigated alternative materials for damping power electronics and lowering noise emissions. Their research led them to an unconventional solution: recycled car tyres.

The researchers developed a granulate from recycled tyre rubber that can be filled into existing cavities within power electronics components. The particles move within these cavities and damp vibrations before they can generate unwanted noise. In laboratory tests, the approach reduced noise levels by 6.5 decibels in the most critical frequency range, while vibrations of a component cover fell by up to 9.7 decibels.

“Particles behave very differently depending on their size, material, filling quantity, temperature, component geometry, and excitation. That’s why simply filling a component with granulate isn’t enough. We must calculate and test which particles, in what quantity and at which location, achieve the best results,” explains Braj Bhushan Prasad, outlining the challenges of the new method.

“Our findings show that even small particles made from recycled tyre rubber can make a noticeable difference in reducing noise in electric vehicles,” says Prof. Hermann Rottengruber. “We now aim to develop this into a tool for designing future electric vehicles, so they not only drive cleaner but also sound more pleasant.”

According to the engineers, the new particle damping technology could in future be used not only in power electronics but also in inverters, control units, and other vibration-prone components of electric drivetrains.

ovgu.de (in German)