There are three basic types of hearing loss: conductive, sensorineural and mixed hearing loss.  
 

• Conductive hearing loss results from a problem with the outer or middle ear.
  Some conditions that may cause a conductive hearing loss in the outer ear include impacted earwax (cerumen), infection in the ear canal (external otitis) or the presence of a foreign body in the ear canal.  Conditions that may cause a conductive hearing loss in the middle ear include middle ear pathologies such as fluid in the middle ear from colds or allergies, ear infection (otitis media), perforations (or holes) in the eardrum, growths in the middle ear and/or a stiffness in the middle ear bones.   An absence or malformation of the outer ear, ear canal, or middle ear can also cause a conductive hearing loss.
   
  When a person has a conductive hearing loss the volume is reduced and sound needs to be made louder in order for them to hear.  This type of hearing loss can often be medically or surgically corrected.  In cases where this is not possible or practical, hearing aids can be fit, often with very good results.
   
• Sensorineural Hearing Loss
  Sensorineural hearing loss occurs when there is damage to the inner ear (cochlea) or to the nerve pathways that lead from the inner ear to the brain. Sensorineural hearing loss has many causes.  Some common causes include noise exposure, viruses, aging and diseases. Sensorineural hearing loss may also be caused by birth injury, genetic syndromes, drugs that are toxic to the inner ear, head trauma and tumors.  
   
  Sensorineural hearing loss is permanent and cannot be medically or surgically corrected.  Sensorineural hearing loss not only involves a reduction in volume but may also affect a person’s ability to hear speech clearly. Patients with sensorineural hearing loss typically are hearing aid candidates. 
   
• Mixed Hearing Loss
  Sometimes a person has both a conductive hearing loss and a sensorineural hearing loss. In other words, there may be damage to both the outer or middle ear and to the inner ear or auditory nerve. This combination of hearing loss is referred to as a mixed hearing loss.

Hearing loss is described in degrees.  The degree of hearing loss is usually classified as mild, moderate, severe or profound or somewhere in-between.  Individuals often have different degrees of hearing loss at different pitches or frequencies.  In general, the greater the degree of hearing loss, the less amount of sound is heard.