Usually, amplification of the sound does rely on a flexible diaphragm which like the skin of a drum is attached along its periphery. But here, Patek Philippe created something different… Instead of a membrane, the system for which Patek Philippe registered three patents has an oscillating wafer made of synthetic sapphire with a thickness of 0.2 mm. Thanks to its angular motion, this rigid and freely movable wafer provides clearly better sound propagation for the confined volume of a wristwatch. Plus, this allows to retain the sapphire caseback and thus the possibility to admire the movement… More here.
This is a stunning watch, but technically Patek has crammed a gramophone into this watch. So unnecessary, so expensive, but great to see this kind of innovation still being attempted.