Chapter 16.4 How You Hear Sound

Pg. 558- 560

The Human Ear• The function of the ear is

to gather sound waves and send or transmit, information about sound to your brain

• Your ear has three main sections:

1. The Outer Ear2. The Middle Ear3. The Inner Ear

• Each section has its own unique function

The Outer Ear

• The outer ear looks and functions like a funnel

• The main function of the outer ear is to funnel sound waves

• The components of the outer ear are the ear canal and eardrum

The Outer Ear• The outer ear collects

sound waves and directs them into a narrow region called the ear canal– The ear canal is a few

centimeters long and ends at the eardrum

• The eardrum is a small tightly stretched, drumlike membrane– Sound waves make your

eardrum vibrate

The Middle Ear• The middle ear is located behind the eardrum • The middle ear contains the three smallest bones

in your body– The hammer• The hammer is attached to the eardrum and vibrates when

the eardrum vibrates• The hammer transmits vibrations to the anvil first and the

stirrups second

– The anvil– The stirrup

Inner Ear• The inner ear is separated from the middle ear by a

membrane – When the stirrup vibrates it vibrates against the

membrane and the vibrations pass into the cochlea

• The Cochlea is a fluid-filled cavity shaped like a snail shell – The cochlea contains more than 10,000 tiny structures

called hair cells

The Inner Ear

• The tiny hair cells have hairlike projections that float in the fluid of the cochlea– When vibrations move through

the fluid the hair cells move, causing messages to be sent to the brain via the auditory nerve

– The brain processes the messages and tells you what you’ve heard

Hearing Loss

• When hearing loss occurs a person may have difficulty hearing soft sounds or high-pitched sounds

• There are many different causes of hearing loss such as, injury, infection, exposure to loud sounds, and aging

Causes of Hearing Loss

• Injury: Hearing loss can occur when the eardrum is damaged or punctured. – This is why it is dangerous to stick objects in your

ears

• Infection: Can cause damage to the delicate inner ear and cause permanent hearing loss

Causes of Hearing Loss• Extended exposure to loud sounds can damage

hair cells in the ear– The damaged hair cells will no longer be able to

send signals to the brain– This type of damage can be prevented!

• Aging: This is the most common form of hearing loss and it occurs gradually – As people get older their hair cells in the cochlea

begin to die ( AND THEY CANNOT BE REPLACED)– People with this kind of hearing loss often have

difficulty hearing high-frequency sounds

Hearing Aids

• For certain types of hearing loss, hearing aids can restore some ability to hear– Hearing aids amplify sounds entering the ear, and

others can amplify specific frequencies that they person has lost the ability to hear

– Hearing aids come in all different sizes

Partner Project• Ask Your Partner what sound they hear

throughout the day – List at least 15 sounds your partner hears– Ask them to rank the sounds they hear ask either

painful, quiet, normal, loud– Then ask them to rate each sound as pleasant, neutral,

or annoying– Also for each sound record the source, location, time

of day, and time exposed to the sound– How are the sound ratings similar? How are they

different?

Sound Source Location Time of day

Time of exposure

Painful, quiet, normal, loud?

Annoying, pleasant, neutral?