Why does metal squeak?
Squeaking metal can be grating on the nerves, but it serves an important purpose.
The slow squeak of a door hinge at 1 a.m. or the screech of a subway train taking a sharp turn may send a shiver down your spine, but why do these noises happen? Why does metal squeak?
It turns out, it's all about the periodic shift between metal pieces sticking and slipping against one another. Metal's stiffness and density also make that squeak extra loud, experts told Live Science.