Some potential causes for muffled hearing in one ear are earwax compaction, otitis media and ear infection, according to HearingDirect. In most cases, muffled hearing in one ear is the result of a treatable condition that doesn't lead to permanent hearing loss.
Doctors and home earwax removal kits can remedy muffled hearing caused by earwax. Q-tips are not a recommended earwax removal method because they can push the wax further into the ear canal, explains HearingDirect. Otitis media is an inflammation of the middle ear that can cause muffled hearing. This condition is most common in children. Ear infections by common viruses can also result in muffled sounds and may require treatment with antibiotics.