What sound should an electric car make? Hybrids have an onboard gas engine that idles and revs but plug-in electrics, the wave of the future, lack internal combustion and are eerily silent.

Now that all the brands are onboard the electric train, much research and development is going into sound for several reasons. Foremost are the drivers, many of whom depend on engine noise to establish speed, and pedestrians, who run a risk due to silent running. My hot-rods deliver a rumble alert but in this age of stealth technology, there is a danger.

As for the driver, even people who aren’t gearheads a...