Hearing Information:
Tutorials/Education
- How We Hear?
- Hearing Loss
Tutorial:
HOW WE HEAR
Of all our senses, hearing is arguably the most complex. With the possible
exception of the brain, the ear may be the most complicated, least understood
organ in the body. At the basic level, the auditory system converts the
energy in sound waves into electrical signals to the brain. The mechanisms
by which this occurs are accomplished in four functional areas: the outer
ear (the external pinna and ear canal), the middle ear (eardrum,
middle ear cavity, middle ear bones), the inner ear (cochlea and
hearing nerve), and the higher neural pathways.
The outer ear collects sound waves in the air and directs them
down the ear canal to the eardrum. The middle ear conducts sound
to the inner ear by changing the signal from a sound wave into mechanical
energy. The eardrum vibrates in response to the sound waves hitting it.
This vibration is transferred to three tiny, connected bones called the
ossicles (also known as the "hammer", "anvil" and "stirrup" due to their
shapes). This transfer results in an increase in the mechanical energy
that is directed to a much smaller opening (oval window) into the inner
ear. The inner ear provides hearing by changing mechanical energy
into electrical impulses that travel to the brain along the auditory nerve.
The cochlea (a snail-shaped structure) in the inner ear contains thousands
of tiny specialized cells, each of which holds many microscopic hairs.
These hairs are immersed in the fluid that fills the cochlea. When the
eardrum vibrates, the middle ear bones move and act as levers to provide
the necessary energy to move the fluid in the cochlea. The movement of
the fluid causes the hairs immersed in the fluid to move. When the hairs
move they, in turn, stimulate the attached cell to send a tiny electrical
impulse along the fibers of the auditory nerve to the brain. The inner
ear also contains structures involved with balance and motion. The higher
neural pathway allows for interpretation of the electrical signal by the
brain. The auditory nerve transmits the electrical signal from the cochlea
to the nerve fibers within the central auditory system where they are
"analyzed" to provide a complex flow of neural information to the hearing
centers of the brain. This neural information is translated by the
brain into the sensation we call "sound". Electrical signals from
both right and left ears reach the auditory centers of the brain that
extract information and stimulate other brain centers to perceive and
recognize speech signals.
Disclaimer: The information provided
on this website is for informational use only and is not intended to be
used as a substitute for evaluation, consultation or diagnosis by a licensed
physician or licensed audiologist. Further, it is not intended to be all-inclusive.
Always consult with your audiologist and primary care physician regarding
matters related to hearing.
