I’m legit surprised more isn’t being done with ultrasonics/infrasonics in the exact areas you describe.

There was one project I worked on to help spec-out and design a device location system at a hospital and one of the solutions we vetted actually used low power ultrasonic exciters producing known and unique patterns paired with tiny little microphone equipped pucks with just enough smarts to record the relative volumes of multiple exciters and send that via radio to a central server along with its own unique ID to be used for triangulation. Ended up being too expensive for us and we went with something based on a combination of BLE and LoRA, but holy shit was the sound based stuff cool (and wouldn’t crowd the radio environment nearly so much, which can be a big deal in ultra dense environments like a hospital.)