Hearing loss may be unilateral (occurring in only one ear) or it may be bilateral (occurring in both ears). Bilateral hearing loss may be symmetrical (the same in both ears) or asymmetrical (the degree, severity and/or configuration of the hearing loss may be different in each ear).
There are three types of hearing loss: conductive hearing loss, sensorineural hearing loss and mixed hearing loss.
- Conductive hearing loss is a mechanical hearing loss due to a problem with the outer or middle ear. The mechanism that conducts sound from our environment to the inner ear, where it is processed into an electrical signal, is not working properly. Examples of conductive hearing loss include blockage of the ear canal by ear wax, a hole in the ear drum, an infection in the middle ear or a problem with any of the three tiny bones of hearing.
- Sensorineural hearing loss is a term used interchangeably with neurosensory hearing loss and nerve hearing loss. Nerve hearing loss is a misnomer because the nerve of hearing is rarely affected. Sensorineural hearing loss almost always happens when the hair cells within the inner ear are not working properly. Examples of sensorineural hearing loss include the genetic hearing loss that most commonly occurs in new born children and the hearing loss common as we all age. Mixed hearing loss means some conductive and some sensorineural.
There are two key aspects to hearing, regardless of the type of hearing loss. One aspect is the ability to hear a sound (pure tones) and the second aspect is the ability to understand words (speech understanding or discrimination). Hearing is useful only if you can understand what you are hearing. Usually, as sound is made louder it also becomes clearer. However, there are some inner ear diseases where the ability to hear a sound is good but speech understanding is poor.