Lecture 21

Question 1

What do we have that helps us hear?

Answer 1

Pair of basilar membranes designed to measure pressure fluctuations over time.

Question 2

What is the structure of the ear and their functions?

Answer 2

Outer- catch sound
Middle- enhance sound
Inner-transduce sounds

Question 3

Do you hear with your ears or your brain?

Answer 3

Your brain

Question 4

What is the pathway of sound to the brain?

Answer 4

Auditory nerve enters the brainstem at the medulla and synapses in the cochlear nucleus-projects to structures in both hemisphere-inputs are then mixed and a single sound perception is formed.

Question 5

What is Heschl’s Gyrus?

Answer 5

Musical analysis-larger in the right hemisphere (primary auditory cortex)

Question 6

What is the PLanum Temporale?

Answer 6

Wernicke’s area, larger in left hemisphere, secondary auditory cortex.

Question 7

What does it mean that the brain has a tonotopic organization?

Answer 7

Structural organization in terms of frequency in the auditory system.

Question 8

What are the 3 ways that we localize sound?

Answer 8

1) Interaural Time Difference
2) Interaural intensity difference
3) Head related transfer function

Question 9

What is interaural time difference?

Answer 9

2 main things: Arrival time- where the sound is located provides information about where the sound is coming from (hits 1 ear before other)
Phase lag: waves are out of sync (continuous) Difference in compression of sound versus non-compression.

Question 10

What are some limitations of the ITD?

Answer 10

Higher frequency sounds have an ambiguous phase lag. Have to use lower frequencies (800hz)

Question 11

What are interaural intensity differences?

Answer 11

Sound shadow- sound is louder at the ear closer to the source (large head gets in way)

Question 12

What are some of the limitations of the interaural intensity difference?

Answer 12

Good dealing with high frequency (over 1600hz), but low frequency waves are larger than the head.

Question 13

What kind of information do ITD’s and IID’s provide?

Answer 13

Information about Azimuth

Question 14

What is head related transfer function?

Answer 14

Pinnae, head shape, etc modify the frequency components differently depending on the sound source.

Question 15

How do we use head tilting behaviour to disambiguate sound location>

Answer 15

Transforms sound into azimuth by tilting the head-azimuth is more accurate for localization in humans than elevation.

Question 16

How is an Owl designed so that information about sound elevation is precise?

Answer 16

Contour feathers, auricular feathers (acoustically transparent-don’t get in the way of sound), and reflector feathers (Border of ruff, channels sound towards ear). Ears are also asymmetrical (left is down, right is up). Loudness of sound provides elevation information.