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.

Noise Exposure in Young Children and Teens

One of the most common ways young children are exposed to excessive noise is via Noisy toys. Many toys are designed to be played further away from the body, but a young child will bring the toy close to their face and ears. By bringing the toy closer to their ears, the resulting sound is louder and therefore more damaging.

The potential risk to your child goes up the louder and longer your child is exposed to the sound. Very loud toys such as a whistle or cap gun can be permanently damaging. When purchasing toys for infants, give preference to toys that have a volume control or an off/on button.  Limit the amount of time that children are expose to sound or remove the batteries. Another option is to cover the loudspeaker with tape to lower the volume.

Check out www.sightandhearing.org and click on “News” and then on “Past News Releases” to see a list of the noisy toys to avoid.

Research has shown that there has been an increase in hearing loss in adolescents during the past three decades. What is even more frightening is that a loss of hearing may go undetected for many years after chronic exposure to high levels of noise. This means that the hearing loss cause by the noise teenagers are exposing themselves to today, might not surface for many years.

Potential sources of noise include playing a musical instrument, attending concerts, occupational exposure such as lawn mowing and using personal headphones to listen to music. Teenagers should be advised to limit the duration and intensity of sound exposure or noisy activities such as concert-going or playing in a band and to use hearing protection whenever engaged in either of these activities.