Chapter 4.3 - The Auditory System

Question 1

How is sound created?

Answer 1

Vibrating objects/molecules or forcing air past a chamber

Question 2

What stimulates the auditory system?

Answer 2

Sound waves, vibrations that travel in air

Question 3

Amplitude

Answer 3

Loudness, measured in decibals (dB)

Question 4

What is Wavelength? What does it’s magnification signify?

Answer 4

Pitch
^frequency(#cycles/second)= ^pitch
Measured in Hz (Hertz)

Question 5

Human range of hearing

Answer 5

Around 20Hz - 20 000Hz

Question 6

Relationship between decibels and loudness

Answer 6

Complex, loudness doubles every 6-10 decibels

Question 7

Risks of higher decibels

Answer 7

Portable hearing devices 100+ decibels, youth and hearing damage

Question 8

Purity of Sounds

Answer 8

Timbre - same note played on violin and French horn

Tuning from is purest

Question 9

Briefly, how do vibrations play a role in the three main parts of the ear?

Answer 9

External ear: vibration of air molecules
Middle ear: vibration of bones
Inner ear: waves in a fluid

Question 10

Parts of the outer ear

Answer 10

Pinna - sound collecting cone, many animals can move to aim

Eardrum/tympanic membrane - taut membrane vibrates from sound waves funnelled by pinna

Question 11

Middle Ear

Answer 11

Mechanical chain 3 ossicles (tiny bones)
Hammer anvil stirrup
Malleus incup stapes
=three stage lever converts lrg mouvement s of lil force into lil movements with big force
=amplify tiny changes in air pressure (round windows)

Question 12

Inner Ear

Answer 12

Cochlea: snail coiled fluid-filled tunnel, enters through ‘oval window’ (vibrated by ossicles)
Basilar membrane: neural tissue with auditory receptors, runs along inside cochlea
Hair Cells: auditory receptors, hair tiny protruding bundles. Convert physical stimulation to neural impulse (like rods & cones)

Question 13

Auditory Processing in the brain

Answer 13

Signals pass through thalamus then auditory cortex (temporal lobes)
Some parallel processing
Medial genicular nucleus: (LGN of ears) part of auditory thalamus - goes to auditory cortex

Question 14

Place theory

Answer 14

Pitch perception depends of vibrations of different places along basilar membrane, hair cells act independently (harp strings)
Hermann von Helmholtz
Wrong: hair cells vibrate together, pattern of vibration

Question 15

Frequency Theory

Answer 15

Pitch depends on frequency (rate) basilar membrane vibrates, whole membrane vibrates at once (drumhead)

Question 16

Two cues to auditory localization

Answer 16

1 - timing of sound arriving at each ear, takes longer to get to one ear
2 - intensity, more intense in one ear helps locate direction, shadow of head, vectors

Question 17

Reconciling Place and Frequency Theory

Answer 17

Both right, whole membrane moves, peaks at specific places depending on frequency

Question 18

Human echolocation

Answer 18

Say “click click click” to judge sound distance bouncing off objects

Question 19

Monaural and binaural cues

Answer 19

1 ear and 2 ears