Regarding the engine sound, I remember seeing a show some time ago (2 Girls Garage?) where the ladies installed a device that added an exhaust sound to a Tesla. So they could probably do the same with an electric motorcycle, dirt or street.
Some of the car manufacturers are piping in the exhaust sound into the cabin through the speakers. BMW got flack for it because it was an artificially created noise, whereas Porsche sampled the real exhaust note being created by the car and amplified it through the speakers.
BMW's new "Reduced" Interior Engine Noise is a Revelation
BMW's new adjustable interior engine noise is a revelation, as it allows drivers to adjust how much fake engine noise comes into the cabin.
www.bmwblog.com
On one hand, it's a nice nod to reducing noise emissions and not annoying pedestrians and other road users around you a la Harley Straight Pipes crowd, but on the other hand, something about that strikes me as being quite unholy and unkosher.