Audition

Question 1

Variance across Species

Answer 1

based on different needs

land/water/air, long distances, high/low frequency sounds, etc

Question 2

External Impact

Answer 2

evolutionary structures of the auditory systems

Question 3

Basilar Membrane and Species

Answer 3

contains hearing receptors - sounds of different frequencies are processed along different areas of the membrane

• cares in length across species
• shorter in amphibians and reptiles, longer in birds, longest in mammals
• longer membrane allows processing of a wider range of frequencies

Question 4

Sound Waves

Answer 4

The Stimulus
Alternating bands of more and less condensed air particles interact with the eardrum to begin auditory processing (compressed air pushes eardrum inward; less dense cause s eardrum movement outwards)
-travel much slower than light waves and require some medium to travel through
-causes the air molecules surrounding the source to move, causing a chain reaction of moving air particles

Question 5

Sound Initiation

Answer 5

vibrating object
burst of air
forcing air through a small cavity

Question 6

3 Psychological sound waves

Answer 6

Loudness
Pitch
Timbre

Question 7

Amplitude

Answer 7

measure of loudness

• greater amplitude = greater intensity/higher waves = louder sound
• measured in decibles
• too loud can cause damage
• 60 decibles = normal convo

Question 8

Frequency

Answer 8

measure of pitch (distance between peaks)

• measured in Hertz (Hz) - number of cycles per second/number of times a second that a cycle is made
• many peaks = high frequency
• audible zone of frequencies that humans can detect represent only a portion of the possible frequencies that can be produced

Question 9

Timbre

Answer 9

measure of complexity/purity
-most of the sounds that we hear everyday are complex sound that are composed of multiple sound waves that vary in frequency

Question 10

The Ear

Answer 10

detects the sound waves and convert them into something that the brain can understand

Question 11

3 Layers of the Ear

Answer 11

External, Middle, Inner

• each area conducts sound in a slightly different way
• incoming changes in pressure are channeled though the external onto the middle, and amplified so it can be detected as changes in fluid pressure, converted into auditory neural impulses

Question 12

External Ear

Answer 12

Pinna
Canal
Eardrum

Question 13

Pinna

Answer 13

folded cone that collected sound waves in environmental and directs along the ear canal

Question 14

Canal

Answer 14

narrows toward ear drum, amplifies incoming sound waves

Question 15

Eardrum

Answer 15

thin membrane vibrating at the frequency of the incoming sound wave and forms back wall of ear canal

Question 16

Middle Ear

Answer 16

other side of eardrum

Ossicles

Question 17

Ossicles

Answer 17

3 Bones called hammer, anvil, stirrup

• create a lever system to amplify vibrations
• convert to waves in the fluid filled inner ear
• 20 times larger than oval window to which it is connected

Question 18

Inner Ear

Answer 18

Coclea
Oval Window
Round Window
Basilar Membrane
Hair Cells

Question 19

Cochlea

Answer 19

fluid field tube about 35mm long

• coiled like a snail shell
• contains neural tissue necessary to transfer changed in fluid to neural impulses of audition

Question 20

Oval Window

Answer 20

small opening in side of cochlea

-when vibrates, causes displacement of fluid in cochlea

Question 21

Round Window

Answer 21

located at other end of cochlea

-accommodates for movements of fluid by bulging in and out accordingly

Question 22

Basilar Membrane

Answer 22

flexible membrane inside cochlea

• when pushed downwards, fluid inside cochlea causes round window to bulge out
• when pushed upwards, round window bulges inwards
• gets wider towards the end
• varies in flexibility and width, so sounds of different frequency cause different areas to vibrate
• higher frequency = near oval window; low frequency = near round window

Question 23

Hair Cells

Answer 23

auditory receptors in Basilar membrane

• move when membrane moves in response to waves in fluid
• movement is converted into neural impulses
• release neurotransmitters when activated and from synapses with bipolar cells, whose axons make up the cochlear nerve
• outnumbered 4:1 but mainly contribute to signal

Question 24

Cochlear Nerve

Answer 24

outer hair cells are more numerous. but slower

• inner hair cells are less numerous but faster and have more connections
• axons synapsed with outer are unmyelinated and thin; axon synapsed with inner are myelinated

Question 25

Cochlear Nucleus

Answer 25

located in hindbrain - has separate dorsal and ventral streams - receives signal from EPSPs in cochlear nerve fibres which are triggered by neurotransmitter released by hair cells

Question 26

Topographical Organization

Answer 26

hair cells connect to the cochlear nerve such that neighbouring regions of hair cells remain together - maintained throughout auditory cortex -different frequencies at different points on basilar membrane - info about similar frequencies are processed together

Question 27

Auditory Localization

Answer 27

ability to locate a source in space based on the fact that our sense organs are separated in space - there is no spatial may for audition - calculated from neural representations of incoming sound - the fact that our ears are located on opposite sides of our head in interaural differences in the sound that give cues for auditory localization - sound must travel farther to reach on ear as opposed to the other which gives cues to localization

Question 28

Time-Difference

Answer 28

measured in sub-milliseconds - dependent on direction of incoming sound - specific neurons in superior olivary complex to thinking of arrival of action potentials

Question 29

Interval Difference

Answer 29

loss of intensity for farther ear - close sounds - detectable - farther sounds - rely in difference in intensity caused by the head which casts a sound shadow - diminished intensity at distal ear - differences can be calculated and compared to determine location

Question 30

Sounds In front/behind

Answer 30

have little difference - harder to locate source - head rotation is a solution

Question 31

Pinna Cues

Answer 31

defracts incoming sound waves to make changes to frequency content - changes - used for localization - ear print =- every ear is different - alteration causes disorienting effect

Question 32

Echolocation

Answer 32

process by which a receiver emits sound pulses and analyzes the returning echo to form a perceptual image of objects in the environment - high frequencies bounce off objects and return to the bats ears - outgoing sound waves - analyzes slight differences in frequency content and timing of returning sound waves to determine characteristics - proximity - still versus motion (doplar) - texture

Question 33

Co-Evolution

Answer 33

the process by which the evolution and adaptation of traits of one species can directly affect the evolution of traits in another species -prey learning to detect bat calls (increases moth survival rate by 40%)

Question 34

Paul Farvue

Answer 34

selective pressures of a predator can drive evolution of a defensive trait of a prey (can result in further selection pressures on predator and so on) -interact individually; locked in arms race