Ears
Your ears collect and process sounds before sending signals to your brain.
The brain reads these electrical signals from sound as recognisable detail – language for example, and music with pitches and tones.
The ear is made up of three different sections: the outer ear, the middle ear and the inner ear. Here’s how they work.
The Outer Ear: Sound Waves
Sounds are collected by the outer ear (the part people see), which is also known as the pinna or auricle. Ear wax is produced in the ear canal, which is part of the outer ear. Ear wax traps dirt and has chemicals to keep the ear canal clean and protect from infection.
The Middle Ear: Vibrations
The middle ear receives sound waves that travel through the ear canal from the outer ear. Its job is to collect these sound waves and convert them into vibrations that are sent to the inner ear. For this to happen, the eardrum, a thin piece of skin stretched tight like a drum, is needed.
The eardrum separates the outer ear from the middle ear and the ossicles, the three smallest bones in your body. Sound waves reaching the eardrum cause it to vibrate. This impacts the ossicles, which in turn pass the sound on to the inner ear.
The Inner Ear: Nerve Signals
Sound enters the inner ear as vibrations and moves into the cochlea, a small curled tube like a snail shell that is the size of a pea. The cochlea is filled with liquid, which is activated when the ossicles vibrate. This vibration causes the cochlea’s tiny cells, covered in tiny hairs, to move, creating nerve signals that the hearing pathway to the brain reads as recognisable sounds.
Video: How Sound is Transferred to the Inner Ear
Types of Hearing Tests
Newborn Hearing Tests
Almost all infants born in Ireland have the newborn hearing screening test before leaving hospital after their birth. Follow-up tests are vital if hearing difficulties are suspected. These types of hearing tests are painless and may be run:
Otoacoustic Emissions (OAE) Test
OAE is used to check a newborn’s hearing in their first few months of life. Painless sonar waves are played from the baby’s ear into their ear-canal through a probe. Responses from the cochlea are measured as an acoustic response. This test is a first confirmation that a baby’s hearing system is working.
Impedance Testing
This type of testing focuses to middle ear reflexes and eardrum mobility, also being known as Tympanometry or Acoustic Reflex tests.
Auditory Brainstem Response (ABR) Test
Three small electrodes are placed on the sleeping baby’s head, with clicks and tones played into tiny headphones over their ears. Like OAE and impedance testing, this test does not measure what the baby can hear, but confirms the sounds to which their brain actively responds.
Audiometry
The child or client goes into a small sound-treated booth where the audiologist plays sounds ranging from low to high pitches. Test responses are recorded onto an audiogram, which shows hearing levels in the left and right ears. Young children can be taught to respond to sounds in the booth by moving toys on a table, or using a thumb-press to signal that a certain pitch was heard.
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