AUDI e sound for electric cars

AUDI ‘e-sound’, a realtime sound generator for electric cars, was developed in the ‘acoustic test bed’ facility shown above

for future use in its electric ‘e-tron’ models, AUDI has developed ‘e-sound’, a realtime technique of generating synthetic motor sounds for the essentially silent vehicle in order to warn pedestrians and cyclists of the car’s proximity. while recent legislative efforts in the US are making it mandatory that companies add artificial engine sounds to electric vehicles, manufacturers are taking the requirement as an opportunity to experiment with the creation of a perfect sound signature to represent the brand.

with the new AUDI system, the ‘e-tron’ car does not broadcast prerecorded engine noises but instead generates sound in realtime to the millisecond, calculated based on data including the electric motor’s rotational speed, vehicle speed, loads, and other parameters. the result is played via a loudspeaker affixed to the undercarriage of the car. each model of ‘e-tron’ is planned to have a unique sound.

during normal operation, the sound produced ranges between five and eight watts, although the system has been tested to handle as much as 40 watts. a small percentage of the sound also enters the vehicle’s interior, but the amount was kept intentionally minimal to maintain the quieter atmosphere that according to the engineers ‘best conveys the unique experience of electric driving.‘

during testing

‘e-sound’ was developed in an ‘acoustic test bed’ facility, a large room whose walls are covered in dense rows of sound absorbers, here 1-meter long wedges filled with glass wool. the space is designed to mimic the sound quality of the wall-less outdoors. in this facility, a dynamometer test bed sits between two rows of microphones, permitting noise to be measured as though the vehicle were driving by.

after extensive testing in the ‘acoustic test bed’, AUDI engineers took the ‘e-tron’ prototype to the streets to evaluate exterior conditions like wind and the sound of other vehicles.

demo of the system and discussion with AUDI engineers about ‘e-sound’

‘some science-fiction films provided inspiration suitable for certain frequency ranges,‘ considers AUDI acoustics engineer rudolf halbmeir. ‘but there was nothing in the real world which offered quite the right sound. when you compose music or sounds, you have to be true to your convictions. the moment you cut corners, you essentially end up with elevator music.‘

view of some of the internal electronics