If it's compact enough to compete with 2-strokes, it's likely way quieter than that. In theory a rotary would be quieter than a similarly powerful spoark-ignited engine due to reduced vibrations, but I don't suspect it's a huge difference.
You can hear it in the video and it is pretty quiet. They've also developed a system where you can shut off the motor and cruise on battery power for short bursts for stealth type applications.