The auditory system processes how we hear and understand sounds within the environment. It is made up of both peripheral structures (e.g., outer, middle, and inner ear) and brain regions (cochlear nuclei, superior olivary nuclei, lateral lemniscus, inferior colliculus, medial geniculate nuclei, and auditory cortex).

Your outer ear consists of your pinna and your ear canal. Your pinna is the visible, external part of your ear. It funnels sound into your ear canal like a reverse megaphone.

Your middle ear consists of your eardrum (tympanic membrane) and your ossicles (tiny, sound-conducting bones called the malleus, incus and stapes). Your eardrum sits at the very end of your ear canal. Your ossicles — located on the other side of your eardrum — carry sound vibrations to your inner ear.

Your inner ear contains a spiral-shaped structure called the cochlea (which means snail shell). Tiny hair cells line the inside of your cochlea. When sound vibrations reach these hair cells, they transmit signals to your auditory nerve.

Your auditory nerve runs from your cochlea to a station in your brain stem (known as the nucleus). From that station, neural impulses travel to your temporal lobewhere your brain attaches sound to meaning.

How does hearing work?

Your hearing process involves all of the auditory system parts mentioned above. Here’s a step-by-step guide to this complex process:

  1. Sound waves travel through your ear canal to your eardrum and cause it to vibrate.

  2. The vibrations travel from your eardrum to your ossicles (tiny bones in your middle ear).

  3. Your ossicles send the vibrations to your cochlea (a spiral cavity in your inner ear that’s lined with hair cells).

  4. The tiny hair cells vibrate and send messages to your auditory nerve (the nerve that connects your ears to your brain).

  5. Your brain receives this information and translates it into sound. In other words, your brain is where your sense of hearing comes to life.

    There are two auditory pathways. These are:

    • The Peripheral Auditory System: This pathway involves the outer, middle, and inner ear. This pathway delivers all types of auditory sensory messages.

    • The Central Auditory System:  This pathway delivers only sensory messages received by the cochlear nucleus.

The auditory system

overresponsive

Auditory over-responsiveness occurs when individuals experience sensitivity to certain sounds or frequencies. Often these individuals notice sounds or audio that others don’t.  Typically, their brain perceives auditory sensory sensations more intensely than others. Because of this, noise sensitivity can lead to sensory or auditory overload.

Some common signs of auditory hypersensitivity include

  • Dislikes loud or unexpected sounds such as fire alarms, sirens, school bells or fireworks

  • May startle easily to unexpected sounds, such as sirens or a motor cycle going past

  • May dislike higher pitched sounds, such as vacuum cleaners or hand dryers

  • Could have difficulty with low hum pitched sounds, such as a refrigerator or lorry engine

  • May be easily distracted by background noises, such as traffic outside, background music, an air conditioner, a refrigerator or buzz from fluorescent lights

  • May notice sounds that others don’t notice

  • May cover their ears to sounds

  • Could dislike the cinema or concerts due to the noise level

  • Hides or cries in response to loud noises at home. For example, the vacuum, blender, a dog barking, etc.

  • Bothered or distracted by small sounds like a clock ticking or water dripping from a tap

  • Afraid of public washrooms -due to the loud flushing toilets, hand dryers, etc

Auditory Processing Disorder (APD) is a disorder of the auditory (hearing) system that causes a disruption in the way that an individual's brain understands what they are hearing.

It is not a form of hearing loss, despite showing difficulty with hearing-related tasks.

People with auditory processing disorder (APD) have a hard time hearing small sound differences in words. Someone says, "Please raise your hand," and you hear something like "Please haze your plan." You tell your child, "Look at the cows over there," and they may hear, "Look at the clown on the chair."

APD, also known as central auditory processing disorder, isn't hearing loss or a learning disorder. It means your brain doesn't "hear" sounds in the usual way. It's not a problem with understanding meaning.

Auditory Processing Dysfunction Can Lead to Difficulties With:

  • Following conversations

  • Knowing where a sound came from

  • Listen to music

  • Remembering spoken instructions, particularly if there are multiple steps

  • Understanding what people say, especially in a loud place or if more than one person is talking

underresponsive

Under-responsive means that they do not notice and process information received from the senses as well. They often seek extra sensory input or they might need support from others to register sensory input.

An individual who is underresponsive to auditory input does not register regular noises in the environment and therefore may not respond to others speaking. It can then appear that the individual is deliberately ignoring friends and coworkers when in fact they may simply not have registered the sound.

Indicators of Auditory Input Seeking:

  • Always speaks loudly

  • Prefers loud music or TV

  • Makes their own noises whenever they are in a quiet environment

  • May create noise by tapping an object on the table, humming, etc.

  • Craves common background noises, for example, may always want the fan running 

  • Puts their ears up against things that are making a sound. For example, toys, TV, a computer speaker, tablet, dryer, etc.

  • Doesn’t respond to important sounds such as an alarm or someone calling their name.

  • Holds radio speakers up against ears

  • Makes silly sounds at inappropriate times or frequently

  • Mimics sounds of others

  • Talks to self

  • Difficulty locating sounds, especially when in a noisy environment

  • Hums in order to hear the sound of humming

    • Play with musical instruments

    • Sing/Make Noise

    • DJing

    • Echolalia

    • Meowing/Animal Noises

    • Clicking sounds, Whistling, Yelling

Examples of Auditory Stimming by Erin @atypical.erin