Hearing Aids and Sound
In order to understand hearing loss, we must first understand sound and how we hear it. Sound is made up of vibrations of
energy which knock together to produce sound waves. The waves travel on air particles, spreading outwards from the
source of the sound.
Sound has two dimensions:
- A - ‘pitch’ or frequency; and
- B - ‘intensity’ or loudness.
Most sounds are made up of different frequencies; they are described as the pitch of a sound. Frequency is measured in
Hertz (Hz), as shown horizontally in the diagram below across the top of the grid. The frequency of a sound affects the pitch
that it is heard at. For example if you look at a piano keyboard from left to right, the low pitch notes are on the left and high
pitch notes are on the right.
Loudness is measured in decibels (dB) and is shown vertically on the left column in the diagram below. The sounds
are getting louder as you move down the column. The diagram shows how loud some everyday sounds can be.
How We Hear
The ear is made up of three different sections: the outer ear, the middle ear, and the inner ear. These parts work together
so you can hear and process sounds. The outer ear, or pinna (the part you can see), picks up sound waves that then travel
down the ear canal.
When the sound waves hit the eardrum, the eardrum starts to vibrate. When the eardrum vibrates, it then causes three tiny
bones in the middle ear to vibrate. These bones are called the ossicles (hammer, anvil and stirrup). They conduct sound
through the middle and into the inner ear.
The vibrations then travel to the cochlea, which is filled with liquid and has thousands of tiny hairs. The sound vibrations
make the tiny hairs move and different hairs vibrate in response to different frequencies. The function of the hairs
is to change the sound waves into electrical impulses that then travel along the auditory nerve to the brain. When the
electrical impulses reach your brain, you ‘hear’ the sound. In order for us to hear sound properly, all parts of the ear must
be working properly