What causes sinus eardrum crackling?

A crackling sound that seems to come from inside the head can be a sign of problems with the Eustachian tubes and middle ear, according to WebMD. The sound can also be the result of pressure changes that occur when the tensor veli palatini muscles open the Eustachian tubes.

When allergies or ear infections cause fluid to build up in the middle ear behind the ear drum, the fluid drains out through the Eustachian tubes, explains WebMD. This can sometimes result in a crackling sound. This sound can also occur when flying in a pressurized aircraft. The Eustachian tubes open to equalize the pressure between the middle and outer ear, and the ears "pop."