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The ear has three main parts: the outer ear, the middle ear, and the inner ear. These three parts work together to create our sense of hearing. Once sound enters the outer ear (the part we see), it travels down the ear canal and hits the ear drum. The three bones of the middle ear (the hammer, anvil, and stirrups) then transmit the sound from the ear drum to the inner ear. Once in the inner ear, tiny hair cells on the cochlea (the main hearing organ) detect the sound and the vibrations it makes in the fluid filled sac of the inner ear. The cochlea transmits these sound messages to the brain through nerves and electrical impulses. This entire sequence takes place in less than a split second, and the result is sound.

There are a number of different types of hearing loss.  Some are caused by infections or diseases, some by deformity or damage to the ear itself, and others by damage to nerves that connect what the ear hears to the part of the brain that interprets what is being heard. 

Hearing loss can be mild, moderate, severe, or profound. 

• Normal hearing: can hear sounds as low as 0-15 decibels (dB)
  The quietest sound that can be heard is 0dB, a light whisper is 10dB.
  
• Mild hearing loss: can hear sounds as low as 20-40dB
  A quiet library is 30dB, a refridgerator hum is 40dB.
  
• Moderate hearing loss: can hear sounds as low as 40-70dB
  A typewriter is 50dB, a conversation at 3-5 feet is 60-70dB.
  
• Severe hearing loss: can hear sounds as low as 70-90dB
  A dial tone is 80dB, near thunder is 90dB.
  
• Profound hearing loss: can only hear over 90dB if at all
  A lawnmower is 100dB, a rock concert is 115-150dB.

Conductive hearing loss is:

• caused by interference in the transmission of sound to the inner ear
• often the result of foreign bodies lodged in the ear, impacted ear wax, a swollen auditory canal, or an ear infection
• an impairment that affects low frequencies and often causes difficulty understanding speech
  
• often seen in infants and young children after ear infections
  
• usually temporary, mild, and treatable with medicine or surgery

Sensorineural hearing loss:

• involves deformity, dysfunction, or damage to the inner ear
  
• usually exists at birth
  
• can be hereditary, but the cause is often unknown
  
• can be mild, moderate, or severe hearing loss
  
• can be progressive (hearing becomes worse over time) or unilateral (in one ear only)
• affects high frequencies, making it difficult to hear telephones, doorbells, and high-pitched voices
• cannot be medically or surgically treated, but hearing aids often help

Mixed hearing loss occurs when:

• both conductive and sensorineural loss are present

Central hearing loss:

• involves the central areas of the brain
  
• often causes difficulty in processing speech and sounds 

Treatment for hearing loss depends on its cause. Many conductive hearing loss problems can be fixed surgically. If surgical correction is not possible, hearing aids can be quite beneficial. While hearing aids cannot restore perfect hearing, they can improve it significantly. Patients with severe to profound sensorineural hearing loss may want to consider cochlear implants. Cochlear implants are surgically implanted medical devices that provide a sense of sound to children and adults who have severe to profound hearing loss and cannot benefit from hearing aids. Hearing aids work by making sound louder and clearer, while cochlear implants create sound by directly stimulating undamaged nerve fibers in the inner ear. Discuss with your doctor which treatment route will be the best for you and your child.