Patient and Parent Education

How We Hear

Ear Anatomy

The ear can be divided up into three parts:  the outer, middle and inner ear.  All three of these sections play an important role in transferring information to the brain for processing. In each case, a breakdown results in a hearing loss.

The OUTER EAR is made up of the ear canal and the eardrum. Sounds, in the form of sound waves, enter the ear canal, travel the length of the ear canal and reach eardrum.  Sound waves bounce off the eardrum, causing a vibration.

The MIDDLE EAR is an air-filled space with the eardrum on one side and the oval window on the other. There are three bones in the middle ear that form a sort of bridge between the eardrum and the oval window.  When the eardrum vibrates, this vibration is transferred via these bones to the oval window. The vibration then is transferred via the oval window to the fluid in the inner ear.

Movement of the fluid in the INNER EAR causes the hair cells in the inner ear to send electrical signals up the auditory nerve to the brain. The brain processes these electrical signals and we “hear” the sound.

Types of Hearing Loss

Problems with sound traveling via the outer or middle ear result in what we call a CONDUCTIVE HEARING LOSS.  Most of these conditions can be medically treated.  Some of the most common factors that result in a problem in the outer or middle ear that result in a hearing loss include:

  • Excessive amount of ear wax
  • Fluid or infection in the middle ear
  • Hole or perforation in the eardrum
  • Deformity of the outer or middle ear
  • Breakage or fixation of the bones in the middle ear
  • Foreign body in the ear canal
  • Growth in the ear canal (exostosis) or middle ear (cholesteatoma)

Issues with sounds traveling in the inner ear are called SENSORINEURAL HEARING LOSS.  For the most part, we can treat the problem via a hearing aid or cochlear implant, but we can’t “fix” the problem medically.  For sensorineural hearing losses in children, we often try to determine if the loss was congenital, meaning present at birth, or acquired at a later age.

The most common reasons for a child having a CONGENITAL hearing loss include:

  • Illness, infection or medicine taken by the mother during pregnancy
  • A condition or syndrome that has hearing loss associated with it
  • Physical abnormality of any part of the ear
  • Hereditary factors

Some of the most common reasons for a child to have an ACQUIRED hearing loss include:

  • Complications at birth
  • Jaundice
  • Illness such as meningitis, scarlet fever or mumps
  • High fever
  • Neurodegenerative disorders
  • Ototoxic medications
  • Head injury or trauma
  • Repeated or constant ear infections
  • Noise (see below)

How to Read an Audiogram

An audiogram is a graphical representation of a person’s hearing. When looking at an audiogram, you will see frequencies/pitches, measured in Hertz (Hz), on the horizontal access (running from left to right- low pitch to high pitch) and Intensity, measured in decibels (dB), on the vertical access (from top to bottom- soft to loud).  A designation is placed on the audiogram for the softest level at a given frequency that your child responds to 50 percent of the time.  An audiogram obtained at Rady Children’s will also report the results of other types of testing such as immittance audiometry and/or otoacoustic emissions results.