Re: I am tempted ..
"to build a little ultrasound broadcasting device, that emits all sorts of random signals just to screw this kind of eavesdropping up."
Just do a web search for ultrasonic deterrents. There are many options to choose from which affect different creatures so likely use different frequency ranges. There's even one for deterring human teens which you may prefer, depending on your live-in family demographics.
Biting the hand that feeds IT
