This is insane. I carefully turned off the two sound sliders on the controller, placed the drone and controller on either side of me, and set up a collision condition. For all of my senses, the drone was beeping.
After reading all the "drone has no buzzer" replies, and looking through several tear downs that sure seem to show no obvious micro-piezo devices, and beginning to think I must be crazy, I tried something else.
On my
Smart Controller, under sound settings, there is some Chinese writing I can't read, nor is there any manual that describes what this feature is. Underneath that toggle, there are several other settings, including some haptic options.
So I went through the list and disabled everything there except the haptic.
The drone is now silent (the haptic warning does work).
Back to how I got here. I'm open to the notion it was an acoustic illusion that the drone was beeping, but you had to be there. Two objects, 90 degrees apart, drone left, controller right, both 3' away. Beep clearly coming from drone. Hard to mess up, right?
At least now I know what to focus on as I get back to DJI on this. If I learn anything new, I'll post it here.