Special Ear Problem (Worksheet)

anvil hammer

oval window

Extenal auditory canal

Cochlea

Ear drum stirrip organ of corti

Round window Basilar membrane

A) Label on the drawing above: 1. External auditory canal 2. ear drum (tympanic membrane) 3. hammer (maleus) 4. anvil (incus) 5. stirrup (stapes) 6. cochlea 7. oval window 8. round window 9. basilar membrane 10. organ of Corti

B) In one or two sentences, what is the function of the outer ear

The outer ear collects sound and guides it to the eardrum.

C) The external auditory canal functions like a 2.5 cm closed pipe. What are the first two resonances of this pipe and how do these explain features of Figure 12-7 on page 354 of your book (Giancoli)?

The first two resonances are about 3500 Hz --- the frequency where your ear is most sensitive --- and 10,5000 --- which corresponds to kinks in the curves of Fig. 12-7.

D)What is the boundary between the outer ear and the middle ear?

The Eardrum

E) In one or two sentences, what is the function of the middle ear?

The middle ear takes the pressure wave coming from the (large area) eardrum and “amplifies” the pressure by about 40 to generate a wave in the fluid of the cochlea through the (small area) oval window.

F) What is the boundary between the middle ear and the inner ear?

The oval window.

G) In one or two sentences, what is the function of the inner ear?

The inner ear generates electrical signals from the (liquid) pressure waves generated at the oval window.

H) That part of the inner ear that detects sound is called the __Cochlea______.

I) Energy from the fluid waves in the inner ear is absorbed by the _basilar membrane.

J) Explain in one or two sentences how the inner ear distinguishes different frequencies.

The basilar membrane is tight and thin at the end near the oval window and absorbs high frequency waves and the organ of Corti turns these into electricity. At its far end, the basilar membrane is thicker and looser and absorbs lower frequency waves.

K) Where are the “hair cells” of the ear located and what is their function (in one or two sentences).

The hair cells are located in the organ of Corti on the basilar membrane. They generate electrical signals when stimulated by waves in the cochlea.