4 ms·

One explanation for ultrasound/microwave is that it's for powering a recording device. If it's solved secret, I would expect them to locate and remove/disable

• bongoman37 5y ago
  Not a spook, but often known devices are not removed because they are a great way to pass on false information. If you know they are listening and they don't know you know they are listening, you could have fake meetings with fake information for them to waste their resources on.
• JohnBooty 5y ago
  Then at that point the signals should stop shortly after because there is no point in powering devices that are no longer working. I think we can think of some good reasons why an adversary might want to continue powering them. Think about it: if we find listening devices, disable them, and the ultrasound/microwaves abruptly stop this would strongly suggest that (1) we've found all the devices (2) the microwaves were indeed specifically for the listening devices (3) the planter of the listening devices is also the party responsible for the ultrasound/microwaves, which is significant because the number of parties that could have physically planted the devices is surely lower than the near-infinite number of parties that could be broadcasting the ultrasound/microwaves. An adversary would surely want to keep us guessing, and would not want us to see such a clear correlation unless that too was an attempt to fool us. So they would likely want to continue with the ultrasound/microwaves even if they weren't getting a response from the listening devices.