I've been to Germany twice now: Once to Berlin and once to Bielefeld.
Both places had these yellow boxes with the same pattern at pedestrian crossings.
At first I thought they were to press for crossing, but there doesn't seem to be any way to actually press them so I'm confused as to what their role is.
What exactly are they for?

Why would a deaf person want to wear such a symbol? So you can tell him/her twice if she has not heard you the first time?
– Jan Mar 22 '19 at 13:12