Ear

Question 1

Define ‘Intensity’ of a sound

Answer 1

The amount of sound energy that passes per second per unit area.
Power per unit area.

Question 2

What are the three sections of the ear?

Answer 2

• The outer ear (pinna and auditory canal)
• The middle ear (ossicles and Eustachian tube)
• The inner ear (semicircular canals, cochlea and auditory nerve)

Question 3

What are the three Ossicles?

Answer 3

Malleus
Incus
Stapes

Question 4

What is the tympanic membrane (eardrum)?

Answer 4

It separates the outer and middle ears.

Question 5

What do both the outer and middle ears both contain?

Answer 5

Air at atmospheric pressure, apart from slight pressure variations due to sound waves.

Question 6

What are the oval and round windows?

Answer 6

They separate the middle and inner ears.

Question 7

What fluid fills the inner ear?

Answer 7

Perilymph

Question 8

What does perilymph allow?

Answer 8

It allows vibrations to pass to the basilar membrane in the cochlea.

Question 9

What do the semicircular canals do?

Answer 9

They help maintain balance

Question 10

What does the pinna do?

Answer 10

It acts as a funnel, channeling the longitudinal sound waves into the auditory canal. The sound energy is now concentrated onto a smaller area, which increases intensity.

Question 11

What do the ossicles act as?

Answer 11

A lever system

Question 12

How does the eardrum vibrate?

Answer 12

The sound waves consist of variations in air pressure, which force the eardrum to vibrate

Question 13

What is the eardrum connected to?

Answer 13

The malleus

Question 14

Where does the malleus pass the vibrations of the eardrum?

Answer 14

To the incus and stapes, which is connected to the oval window.

Question 15

What functions do the ossicles have?

Answer 15

• Transmitting vibrations
• Amplifying the force of the vibrations by around 50%
• Reducing the energy reflected back from the inner ear

Question 16

What results in greater pressure variations at the oval window?

Answer 16

• The oval window has a much smaller area than the eardrum

- The increased forced produced by the ossicles

Question 17

How big are the pressure variations at the oval window?

Answer 17

20 times bigger than the variations at the eardrum

Question 18

Where does the oval window transmit vibrations to?

Answer 18

The fluid in the inner ear

Question 19

What makes the basilar membrane vibrate?

Answer 19

The pressure waves in the fluid of the cochlea.

Question 20

What is the natural frequency of the ear?

Answer 20

Ranges from 20,000 Hz near the middle to 20 Hz at the other end

Question 21

What happens when a sound wave of a particular frequency enters the inner ear?

Answer 21

One part of the basilar membrane resonates and so vibrates with a larger amplitude.

Question 22

What do the hair cells do?

Answer 22

Hair cells attached to the basilar membrane trigger nerve impulses at this point of greatest vibration, and these electrical impulses are sent, via the auditory nerve, tot he brain, where they are interpreted as sounds.