Bell RingerBell Ringer

1. How would your life be effected if 1. How would your life be effected if you suddenly lost your hearing?you suddenly lost your hearing?

2. How would your life be different 2. How would your life be different if you were never able to hear?if you were never able to hear?

How does hearing How does hearing effect behavior?effect behavior?

Section 3.3 p 77-80Section 3.3 p 77-80

ObjectiveObjective

Students will be able to:Students will be able to:

- Define sound and how it is measured- Define sound and how it is measured

- Name the major parts of the ear- Name the major parts of the ear

- Trace the path of a sound from the - Trace the path of a sound from the outer ear to the auditory cortex of outer ear to the auditory cortex of the brainthe brain

- Discuss the dangers of excessive - Discuss the dangers of excessive noisenoise

Key TermsKey Terms

Auditory nerve: carries impulses form the cochlea to the Auditory nerve: carries impulses form the cochlea to the auditory cortex of the brainauditory cortex of the brain

Cochlea: snail shaped; filled with fluid and hair cells; Cochlea: snail shaped; filled with fluid and hair cells; converts sound energy into electrical impulseconverts sound energy into electrical impulse

CPS: cycles per second, measure of a sound waveCPS: cycles per second, measure of a sound waveDecibel scale: used to measure the range of sound to Decibel scale: used to measure the range of sound to

which the ear can respondwhich the ear can respondEardrum: thin, flexible layer of tissue that stretches Eardrum: thin, flexible layer of tissue that stretches

across the end of the auditory canal; vibrates when across the end of the auditory canal; vibrates when sound waves strike itsound waves strike it

Frequency: # of vibrations/sec.Frequency: # of vibrations/sec.Sound: a form of energy consisting of air waves of Sound: a form of energy consisting of air waves of

changing pressurechanging pressureThree-bone lever: magnifies the vibrations transmitted Three-bone lever: magnifies the vibrations transmitted

by the eardrum by the eardrum

What is sound?What is sound?

If a tree falls in the woods and If a tree falls in the woods and no one is there to hear it, does no one is there to hear it, does it make a sound?it make a sound?

An object produces sound when An object produces sound when it vibrates it vibrates air particles. air particles.

Waves are divided into: Waves are divided into:

Compression Compression

Rarefaction Rarefaction

How is sound defined? How is sound defined?

Frequency (Frequency (λλ)) = = PitchPitch

Amplitude = VolumeAmplitude = Volume

What are the major What are the major parts of the ear? parts of the ear? Pinna (pl. pinnae), Pinna (pl. pinnae),

the outer part of the outer part of the earthe ear

Functions: Functions: - Determines Determines

direction of direction of soundsound

- Increases Increases amount of sound amount of sound caughtcaught

What are the different What are the different ways we determine ways we determine direction of sound?direction of sound?Single Pinna: cues of direction: Single Pinna: cues of direction:

up/down/turn-aroundup/down/turn-aroundTwo Pinnae: Horizontal position of a Two Pinnae: Horizontal position of a

sound by comparing the sound by comparing the information coming from your two information coming from your two ears. ears.

Ex. If the sound is to your left, it will Ex. If the sound is to your left, it will arrive at your left ear a little bit arrive at your left ear a little bit sooner than it arrives at your right sooner than it arrives at your right ear. ear.

-Pinnae face forward: front > -Pinnae face forward: front > behind.behind.

Articulated pinnae: focus on sounds Articulated pinnae: focus on sounds from a particular direction. from a particular direction.

Human pinnaeHuman pinnae lay fairly flat against the headlay fairly flat against the headNo muscles for significant No muscles for significant

movement. movement.

What are the major What are the major parts of the ear?parts of the ear?EardrumEardrum = tympanic = tympanic

membranemembrane10 millimeters (0.4 inches) 10 millimeters (0.4 inches)

wide. wide. The middle ear is connected The middle ear is connected

to the throat via the to the throat via the Eustachian tube. Eustachian tube.

Air pressure on both sides of Air pressure on both sides of the eardrum remains the eardrum remains equal. equal.

The eardrum is rigid, and The eardrum is rigid, and very sensitive.very sensitive.

Even the slightest air-Even the slightest air-pressure fluctuations will pressure fluctuations will move it back and forth. It move it back and forth. It is attached to the tensor is attached to the tensor tympani muscle, which tympani muscle, which constantly pulls it inward. constantly pulls it inward.

How does the structure How does the structure of the ear protect us of the ear protect us from loud sound?from loud sound?When the brain When the brain

receives a signal receives a signal that indicates that indicates loud noise. The loud noise. The tensor tympani tensor tympani muscle suddenly muscle suddenly contract. This contract. This pulls the pulls the eardrum/bones eardrum/bones away, drum away, drum becomes more becomes more rigid.rigid.

How is sound wave How is sound wave turned into neural turned into neural impulse?impulse?Cochlea in the inner ear Cochlea in the inner ear

conducts sound conducts sound through a fluid, through a fluid, instead of through air. instead of through air. This fluid has a much This fluid has a much higher inertia than air higher inertia than air

Force felt at the Force felt at the eardrumeardrum would not would not move fluid. Before the move fluid. Before the sound passes on to sound passes on to the inner ear, the the inner ear, the total pressure (force total pressure (force per unit of area) must per unit of area) must be amplified. be amplified.

OssiclesOssiclesbones of middle ear. the bones of middle ear. the

smallest bones in your smallest bones in your body. They include: body. They include:

What are the ossicles?What are the ossicles?

Malleus Malleus hammer hammer

Incus Incus anvil anvil

Stapes Stapes stirrup stirrup

How do ossicles How do ossicles amplify force?amplify force?Ossicles move so that the Ossicles move so that the

faceplate. faceplate. Size difference between Size difference between

the eardrum and the the eardrum and the stirrup. stirrup.

Eardrum SA 55 mm,Eardrum SA 55 mm,Faceplate SA 3.2 square Faceplate SA 3.2 square

millimeters. millimeters. When you concentrate this When you concentrate this

energy over a smaller energy over a smaller surface area, the surface area, the pressure (force per unit pressure (force per unit of volume) is much of volume) is much greatergreater

22 times the pressure felt 22 times the pressure felt at the eardrum. at the eardrum.

Think High heels…Think High heels…

How does the cochlea How does the cochlea function? function?

Most complex part of the earMost complex part of the ear physical vibrationsphysical vibrations electrical information electrical information

How does the cochlea How does the cochlea function?function?The basilar The basilar

membranmembrane has a e has a peculiar peculiar structure. structure. It's made It's made of 20,000 of 20,000 to 30,000 to 30,000 reed-like reed-like fibers fibers that that extend extend across across the width the width of the of the cochlea. cochlea.

Hearing ReviewHearing Review

The basic concepts at work in The basic concepts at work in human and animal ears are human and animal ears are fairly simple, but the specific fairly simple, but the specific structures are extremely structures are extremely complex. complex.

Label the Parts of the Label the Parts of the EarEar