What Is Stick-Slip (Why Hinges Squeak)?
Quick answer
A squeak is just two dry metal parts gripping and letting go hundreds of times a second.
The physics behind a squeak: two dry metal surfaces alternately gripping and releasing hundreds of times per second, fast enough to become an audible tone. A film of grease with body (lithium or silicone) keeps the surfaces apart, which is why it silences a hinge and thin penetrating oils only pause it.
Fixes that use this
Walls, Doors & Floors
Fix a Squeaky Door Hinge for Good (WD-40 Isn't Enough)
WD-40 quiets a hinge for a week. Pulling the pin and coating it with silicone or lithium grease fixes it for years. Here is the 5-minute method.
Time5 min per door Cost$6–$8 easy