Question Earpiece/ led impermeability

Hi, how is granted the impermeability of the earpiece and notification led?
On my Z1Compact the tiny membrane visible over led seems to be connected only on two sides, leaving the upper side merely close up to the plastic frame. From a close observations is possible to see a space small enought to insert a slim piece of 3M Scotch (i've noticed the first time during the first led blink).
I suppose the led underneath and the earpiece are water shielded otherwise: because i have already tested twice (for a total of 10 min.) on a water recipient whitout visible infiltrations or failure.
On the teardown photo this area is non visible.

Do you have any news concerning it?

front: https://dl.dropboxusercontent.com/u/...322_174713.jpg
back: https://dl.dropboxusercontent.com/u/...322_174856.jpg
Samsung Galaxy Note 2 - Xperia SP - Nokia Lumia 820