Interesting sound comparison here of the Audi R18 e-tron quattro and Audi R18 ultra. Enjoy!
Another talking point is the difference in sounds of the cars. Both have the same diesel engine and hence sound the same during the bulk of the lap. The e-tron has a few different sounds when the hybrid system is activated at over a 120km/h and under breaking when the regenerative cycle of the system comes into effect. The e-tron has a “whirling” whistle type sound during these instances. One could almost describe the hybrid system as sounding like a “spaceship”.