Force sensor on AirPods 3, AirPods 4 (both models), and AirPods Pro 1
A force sensor is located along the stem of AirPods 3, AirPods 4 (both models), and AirPods Pro 1.

The force sensor on AirPods 3
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The force sensor on AirPods 4 (both models)

The force sensor on AirPods Pro 1