Chapter 10 - Hearing

Question 1

What is sound?

Answer 1

Audible variations in air pressure

Question 2

What is the pitch or sound frequency?

Answer 2

Number of cycles per second expressed in Hertz

Question 3

What is intensity or amplitude?

Answer 3

Difference in pressure between compressed and rarefied patches of air

Question 4

How do you calculate the sound pressure level (SPL)?

Answer 4

20log(Pmeasured/Pref)

Question 5

What are the three parts of the ear?

Answer 5

• outer ear: pinna conducts sounds into the auditory canal toward the tympanic membrane
• middle ear: tympanic membrane, ossicles (malleus, incus, stapes)
• Inner ear: cochlea

Question 6

What are the 5 steps of sound in the ear?

Answer 6

• sound waves move tympanic membrane
• tympanic membrane moves ossicles
• ossicles move membrane at oval window
• motion at oval window moves fluid in cochlea
• movement of fluid in cochlea causes response in sensory neurons

Question 7

What are the two impedance matching mechanisms to overcome energy mismatch between air and water?

Answer 7

1) lever-arm ratio:
a) ossicles act as levers
b) malleus arm is shorter than incus arm so small movements in malleus = large movements in incu

2) area ratio:
a) amplification due to the larger area of the tympanic membrane compared to the footplate of the stapes in the oval window
b) pressure=force/area