Hearing

Question 1

How is sound caused?

Answer 1

by changes in air pressure

Question 2

What is amplitude?

Answer 2

• decibels: dB
• related to loudness

Question 3

What is frequency?

Answer 3

• Hertz: Hz
• related to pitch

Question 4

What is a phase (in a pressure wave)?

Answer 4

the position within a cycle

Question 5

What is a pure tone?

Answer 5

• sine wave
• simplest sound wave

Question 6

What is Fourier analysis?

Answer 6

the process of decomposing complex sounds into their sine wave components

Question 7

What is the lowest frequency component of a complex sound?

Answer 7

the fundamental

Question 8

*What are many complex sounds made up of?

Answer 8

harmonics—integer multiples of the fundamental

Question 9

What are the three main areas of the outer ear?

Answer 9

• Pinna
• External auditory canal
• Eardrum (tympanic membrane)

Question 10

What is the function of the PInna (outer ear)?

Answer 10

• increases the sound amplitude
• helps determine the direction from which a sound is coming

Question 11

What is the function of the external auditory canal (outer ear)?

Answer 11

• provides protection
• increase the sound amplitude

Question 12

What is the function of the eardrum (outer ear)?

Answer 12

• vibrates in response to sound waves
• moves bones in the middle ear

Question 13

What are the three bones (ossicles) of the middle ear?

Answer 13

Malleus
Incus
Stapes

Question 14

What are the functions of the ossicles (middle ear)?

Answer 14

transmit vibration of the eardrum into the choclea through lever actions

Question 15

What does the inner ear consist of?

Answer 15

semicircular canals - sense of orientation
cochlea

Question 16

How does the cochlea (inner ear) work?

Answer 16

it is filled with liquid which moves in response to the vibrations coming from the middle ear

Question 17

What are the three canals on the cochlea (inner ear)?

Answer 17

• Vestibular canal
• Tympanic canal
• Cochlear duct

Question 18

What separates the canals of the cochlea (inner ear) and what is the function of the membrane?

Answer 18

basilar membrane
- converts vibrations into neuron signals

Question 19

What is the central auditory pathway?

Answer 19

• nerve fibres from each cochlea synapse in a number of sites (nucleus’s) on the way to the primary auditory cortex
• input from both ears is present in both hemispheres
• seems that the cortex deals with more complex auditory tasks while the lower structures deal with simple aspects of sound (sound perception is beyond PAC)

Question 20

How is the frequency of a sound processed in frequency coding?

Answer 20

• waves travel along the basilar membrane and peak at different points depending on the frequency of the sound
• the location of the peak identifies the frequency of the sound

Question 21

How is the pitch of a sound processed in frequency coding?

Answer 21

simulating auditory nerves at different cochlea locations leads to the perception of sounds in different pitch

Question 22

What happens if a fundamental is missing however the harmonics are present?

Answer 22

the missing fundamental is filled in

Question 23

What are the two basic mechanisms for loudness perception and how does it work?

Answer 23

• overall firing rates
• range of firing

More neurons fire when a sound is more intense, each neuron fires more vigerously

Question 24

ctors impact loudness?

Answer 24

• duration of sound (longer = louder)
• frequency (higher frequency = louder sound)

Question 25

What occurs in the binaural process of auditory space perception?

Answer 25

interaural time difference - onset difference - phase difference interaural intensity difference

Question 26

What is the onset difference in the interaural time difference?

Answer 26

Unless a sound is directly in front of or behind you, it reaches two ears at different times

Question 27

What is the phase difference in the interaural time difference?

Answer 27

The same sound will most likely be in different phases when it reaches each of the two ears

Question 28

What is Interaural intensity difference?

Answer 28

- The same sound should be a bit more intense at an ear that is closer to the sound source - The energy of a sound decreases as it travels farther - The head works as a barrier that reduces the intensity of the sounds (sound shadow)

Question 29

What is the Interaural time difference useful for?

Answer 29

localizing low-frequency sounds

Question 30

What is Interaural intensity difference useful for?

Answer 30

localizing high-frequency sounds

Question 31

What direction are we better at percieving?

Answer 31

* Humans perceive horizontal directions better than vertical directions through auditory cues

Question 32

What are the two cues for auditory distance perception?

Answer 32

○ Loudness cues can tell us only about relative distance ○ Reverberation cues vary depending on various properties of the reflection surface