Porsche  

I dread the day the internal...
I dread the day the internal combustion engine noise is replaced by a whirling sound.

.
Really? I can't wait for it, for all sorts of reasons but to be selfish mostly because of noise, I get enraged by neon light, leaf blowers, lawn mowers etc and can't understand why other people don't.
I look forward to the far quieter and cleaner city, I never understood why people thought Gattaca was dystopic.
I agree though that some sports cars feel more suited to electric power than others, the 911 perhsps but others suit a zzzzwooosh or a hum.

You have the Tesla electric...
You have the Tesla electric sports car fitted with a sound module which replicates the sound of a piston engine
video below
http://www.youtube.com/watch?v=pJddxXP4obI&feature=related

and other propulsion systems...
and other propulsion systems 🙂
http://www.youtube.com/watch?v=j2TofIv30p8&feature=related

poach
I'm afraid that the throaty sound of the boxer 6 was already sucked of the 911 back in 1998. That's when the 911 air cooled boxer 6 went to a water cooled.
Porsche was forced to this in order to comply with new noise regulations in Germany

I had a Prius
sneak up on me in a narrow lane, while I was walking. It was a bit unnerving -- though the car wasn't speeding or trying to run me over. I never heard it until it was upon me.