I know, it sounds weird, but it sounds like the characteristic start-up sound that the ESC makes comes from the motor. I disconnected the motor and started the ESC up, and it made the same sound, except a LOT softer, directly from the ESC.
So, where's the sound coming from and what does the motor have to do with it? A simple conclusion is that the motor is being used as a speaker but then the next question is... how??? As far as I know, the motor doesn't have anything equivalent to the uhhh...vibrating membrane of a speaker. Well.... wait... Maybe it's vibrating the motor's "Bell" or "Skirt" or "can" or whatever it's called.
So, where's the sound coming from and what does the motor have to do with it? A simple conclusion is that the motor is being used as a speaker but then the next question is... how??? As far as I know, the motor doesn't have anything equivalent to the uhhh...vibrating membrane of a speaker. Well.... wait... Maybe it's vibrating the motor's "Bell" or "Skirt" or "can" or whatever it's called.