> The problem seems to be that sound cards (or chips) in modern PCs are too clever for their own good. They are designed to optimise microphone input for Skype and Zoom and that means removing the noise and extraneous clicks that are exactly the signal that the detector puts out.

Ugh! I wonder what other hidden features are lurking on my laptop hardware. I am conflicted because while I understand perfectly well why market forces compel hardware manufacturers to add these "features", I don't like the idea of not being able to trust my primary computing hardware.