The Auditory System

The ear can hear many different sounds either through air-conduction or bone-conduction. These sounds must be accurately received by the ear, then be sent to relevant parts of the brain to be analysed and acted upon.

In the case of language, spoken words are received as sound pressure waves. In the middle ear the sound pressure waves are converted to vibrations of the ear bones and transmitted through the bone to the inner ear. Here the vibrations are subsequently converted into electrical impulses, which are in turn sent to the brain cortex and the temporal lobe where the signals are interpreted as words. It is at this point that the meaning of the sounds is decoded. Once the meaning is assigned, the brain can then move to the task of evaluating the information and forming response strategies.

It is vital that the ear correctly perceives sound so that the organs of the inner ear, the cochlea (the decoder of every sound we hear) and the vestibule (the centre for sensory integration and motor control), can convert the sound to electrical signals for the brain to receive. If this does not occur the other stages of processing will be affected.

The cochlea and vestibule comprise the inner ear and complement each other. Where the cochlea attends to short wavelengths characteristic of external sound, the vestibule attends to the long wavelengths produced by physical movements.

Auditory processing is a term used to describe what happens when your brain recognizes and interprets the sounds around you. Humans hear when energy that we recognize as sound travels through the ear and is changed into electrical information that can be interpreted by the brain.

Auditory Processing represents the actual quantity of pieces of information taken in by the auditory area of the brain, not the organs themselves.  Processing is defined as how well the brain understands, interprets or categorizes information.

The “disorder” part of auditory processing disorder (APD) means that something is adversely affecting the processing or interpretation of the information.

Children with APD often do not recognize subtle differences between sounds in words, even though the sounds themselves are loud and clear. For example, the request “Tell me how a chair and a couch are alike” may sound to a child with APD like “Tell me how a couch and a chair are alike.” It can even be understood by the child as “Tell me how a cow and a hair are alike.” These kinds of problems are more likely to occur when a person with APD is in a noisy environment or when he or she is listening to complex information.

APD goes by many other names. Sometimes it is referred to as Central Auditory Processing Disorder (CAPD). Other common names are auditory perception problem, auditory comprehension deficit, central auditory dysfunction, central deafness, and so-called “word deafness.”

In order for the brain to process information it must first have the ability to hold individual pieces of information together—short-term memory. To understand, categorize, and interpret the individual pieces, the brain must first arrange them into some type of order. Generally, the level of language or ability to follow directions is a reflection of the individual’s level of processing.

The “Normal” two year old understands only two-step directions (get shoes, eat dinner, go ride) and speaks in couplets (want eat, no bed). A three year old processes three (simple phrases); a four year old, four; and on up to seven year old to adults. A seven year old or older should be able to understand and remember seven bits of information. That’s one reason phone numbers are only seven digits!

Short-term memory lasts only a second. For example, someone tells you a phone number and you repeat it a billion times until you can write it down; each time you repeat the number is how long your auditory short-term memory is.  The individual above age seven who holds 3,4, or 5 pieces of information together is struggling—to learn, to behave; they may have problems with mobility or speech, even functioning in daily life.

One factor affecting opportunity is hearing itself.  If a child’s hearing is impaired, obviously that child will take in less information. The brain learns to see by seeing and to hear by hearing. Hearing loss, ear infections, and allergies or sensitivities all affect the quantity and quality of information our brain receives.

SIGNS OF AUDITORY DYSFUNCTION: (no diagnosed hearing problem)

1. HYPERSENSITIVITY TO SOUNDS (auditory defensiveness):

  • distracted by sounds not normally noticed by others; i.e., humming of lights or refrigerators, fans, heaters, or clocks ticking
  • fearful of the sound of a flushing toilet (especially in public bathrooms), vacuum, hairdryer, squeaky shoes, or a dog barking
  • startled by or distracted by loud or unexpected sounds
  • bothered/distracted by background environmental sounds; i.e., lawn mowing or outside construction
  • frequently asks people to be quiet; i.e., stop making noise, talking, or singing
  • runs away, cries, and/or covers ears with loud or unexpected sounds
  • may refuse to go to movie theaters, parades, skating rinks, musical concerts etc.
  • may decide whether they like certain people by the sound of their voices

HYPOSENSITIVITY TO SOUNDS (under-registers):

  • often does not respond to verbal cues or to name being called
  • loves excessively loud music or TV
  • appears to “make noise for noise’s sake”
  • seems to have difficulty understanding or remembering what was said
  • appears oblivious to certain sounds
  • appears confused about where a sound is coming from
  • talks self through a task, often out loud
  • had little or no vocalizing or babbling as an infant
  • needs directions repeated, says “what” frequently

The Seven Senses