Something a bit like the SoundRacer then?
Yep, you hit exactly I was thinking about, but didn't realized it is already done, so we'll see if it could be usable but sounds great
Electric Vehicle Electronic Engine Sound System
http://eveess.com/Module is described there:
http://eveess.com/evsm-2/http://eveess.com/evsm-input-signals/It looks like signal from hall sensor can be taken and this module recognizes voltages above 3V as pulses, so quite easy to integrate and demo from CEBIT 2013 there:
Comparision of EV with Soundracer enabled and than disabled there: SoundRacer EV V8 - EVEESS - Shelby V8 sound
In the middle of this video above we have Zero Emmision EV with engine sounds enabled at parking and it sounds like... V8 engine
After watching a few sample sounds those F12 sounds in classic ICE car are not so bad, but... they should allow in this sounde module multiply sensed bloody classic car RPM speed sensed from alternator ripple, to be somewhere closer to F12 engine and probably forgot about it
SoundRacer V12 Ferrari sound
Anyway, probably custom speakers and amplifier will be needed to adjust sound loud level to external environment, while in quiet places we do not want of course disturb beaty of silence, but ensure someone walking or on a bike can hear electric vehicle because it is what we have in our brains trained in neurons unconscious mind and in stress situations if someone doesn't hear something and can't see it it doesn't exist.
Quoting again from this web site linked above they wrote something like this, so I'm prety sure it is a good way to go and implement such exhaust pipes engine sound subsystem for safety reasons and I was thinking about low frequency sounds, while they are easy to sense whil emany things vibrate at those frequencies
Electric Vehicle Electronic Engine Sound System
http://eveess.com/Sound for increased safety
The silence of electric vehicles is highly appreciated by most drivers, passengers and people outside the vehicle. But in some situations a warning sound is required in order to increase safety for people in front of the vehicle. SoundRacer EVS is designed to help EV manufacturers meet the upcoming legislation’s for pedestrian warning sound.
In USA, the Pedestrian Safety Enhancement Act that the National Highway Traffic Safety Administration (NHTSA) proposed on July 7, 2011 is ”the first major step towards regulations that will protect unsuspecting pedestrians and the visually-impaired from accidents involving hybrid and electric vehicles.”
Sometimes drivers have to think on the road instead of other people to avoid collisions:
"... Protect unsuspecting pedestrians and the visually-impaired from accidents involving hybrid and electric vehicles ..."Yep, so no question about it, but it should be smart solution and should allow sense environment noise level to adjust output volume, so we need to find a way to sense sound outside vehicle, while inside we might want listen to music and had no idea if someone can hear us on the streat