Infection : Infection and inflammation in the outer ear (otitis externa) or middle ear
Wax (cerumen) : A build-up of wax in the outer ear may stop sound from reaching the ear drum
Hole in the eardrum (perforation) : A hole in the ear drum may be caused by several things including trauma (damage), pressure, ear surgery and infection
Glue ear : Irritation in the center ear with related liquid filling the center ear space around the ossicles. The liquid stops the ossicles and ear drum from moving viably and prevents sound from going effortlessly through to the inward ear.
Problem with the small bones (ossicles) : Stiffening of the chain of small bones in the middle ear prevents sound from passing easily through to the inner ear.