When operating in quiet mode, both proposed bikes rely on a lithium-ion electric battery, which keeps the noise down to around 55 decibels, about as loud as an indoor conversation.
The bike has cutting-edge hybrid multi-fuel engines that can burn a variety of combustibles like JP-8, Jet A-1, gasoline, propane, etc.. “If it’s gasoline, tell it it’s gasoline, tell it it’s something else. It will figure it out,” said Alex Dzwill, and engineer with Logos.
Naturally, if it's running on fuel, it's about as loud as a garbage disposal - not quiet. But it will be used to get near to the enemy, where they will switch to stealth mode. Interesting.