MrFloppy

I think "Draisy" is faster on the track and a much more realistic project. But "Monocab" is a University project, so it's ok for me that a few millions are invested there.

It's only for the alpha-test vehicles. The crane does not touch the rails, it's a security issue for testing e.g. min power gyro

Before you try a complex diy solution you already have tried a easy solution, like "Animation away" from "Royal Gardeneer" or similar gadgets which create a ultrasound siren?!? And if this 20,- EUR/USD Gadget is not working for these dogs, you could open it and use 99% of the device to add an mp3-circuit-board.