on the scout, you have the Moster 185 producing all the noise, plus a little bit of noise from the propeller
On the OpenPPG, there’s very very little noise coming from the electric motors itself, whereas most of the noise is coming from the air being moved by the four (smaller) propellers.
There’s a nice video from Rob ( @SimLoop ) which gives a nice comparison between the OpenPPG and three 2-stroke PPGs: