Apple does not secretly analyze sine waves to infer head motion. Instead, airpods pro/max/gen-3 include actual IMUs (inertial measurement units), and ios exposes their readings through core motion.
It’s a known research technique called acoustic motion tracking (some labs use inaudible chirps to locate phones or headsets) you mentioned, but it’s not how airpods head tracking works
It’s a known research technique called acoustic motion tracking (some labs use inaudible chirps to locate phones or headsets) you mentioned, but it’s not how airpods head tracking works