William Gallagher, AppleInsider:
You can already get your lost iPhone or iPad to play a sound through Find My, but Apple is researching how the devices can signal and relay locations to each other without audible beeps or tones.
Even though the bleeping that Find My makes AirPods do is surprisingly loud, there’s only so loud it can possibly be from such a small device. Apple has plans for how this same system can be improved by cutting you out of the equation.
“Locating wireless devices” is a new US Patent that describes how devices can use sound outside the range of human hearing.
Part of the issue with Find My is the granularity of the search. As is, it certainly can tell you if your device is in your house but, beyond that, it’s not that useful to pinpoint your iPhone amongst the clutter.
Sound works great to locate your iPhone, but as William points out, there’s only so loud your AirPods can get, especially if they’re buried behind a couch cushion, or under a couch.
An inaudible signal between devices might make this search much easier, using directional signals known as beamforming.