This is stupid; if I'm going to be able to sneak an entire robot vacuum cleaner into the victim's environment, I'm putting an actual microphone and even camera in there, and not messing around with LIDAR bouncing off vibrating paper cups.
You work with what you have. Ideally you'd have a microphone, but maybe that robot vacuum cleaner of your target doesn't have one. And maybe you also don't have access to other devices which have one.
But, TBH, I wouldn't be surprised if today's vacuum cleaners have a microphone in them. "For voice commands", you know?
Recently I bought another TP-Link HS110 Wifi Plug, and while working on reading it automatically every couple of seconds with a Python script, I noticed that a response contained a field labeled "mic_type":"IOT.SMARTPLUGSWITCH". "mic_type"?
Some time ago the German router producer "AVM" had to explain why their DECT smart-plugs had a microphone in them.
But a clever hacker would probably drive the vacuum cleaner to a better location and then make the "low battery" led blink and leave it there ;)
Most people didn't realize that the :visited selector represented a danger until someone figured out how to get your browsing history by abusing it.