In addition to supporting MagSafe charging magnets, a shorter stem, and spatial audio support, the new AirPods 3 have improved in-ear position detection.
In AirPods 2 version | AirPods Pro use infrared sensors to provide in-ear position detection. But they are easy to deceive if you hold them in your hand, put them on the table, and so on.
The third generation of AirPods 3 received an improved skin detection sensor that will more accurately determine the position to prevent accidental playback. For this, PPG (photoplethysmography) technology is used with four SWIR (short wave infrared) LED chips, as well as two InGaAs photodiodes.
Interestingly, based on this technology, tracking of heart rate and blood oxygen levels can be implemented. The new AirPods 3 will retail for $179 (US, excluding taxes and shipping).
A source: 9to5mac