Chapter 4.3 - The Auditory System Flashcards
(19 cards)
How is sound created?
Vibrating objects/molecules or forcing air past a chamber
What stimulates the auditory system?
Sound waves, vibrations that travel in air
Amplitude
Loudness, measured in decibals (dB)
What is Wavelength? What does it’s magnification signify?
Pitch
^frequency(#cycles/second)= ^pitch
Measured in Hz (Hertz)
Human range of hearing
Around 20Hz - 20 000Hz
Relationship between decibels and loudness
Complex, loudness doubles every 6-10 decibels
Risks of higher decibels
Portable hearing devices 100+ decibels, youth and hearing damage
Purity of Sounds
Timbre - same note played on violin and French horn
Tuning from is purest
Briefly, how do vibrations play a role in the three main parts of the ear?
External ear: vibration of air molecules
Middle ear: vibration of bones
Inner ear: waves in a fluid
Parts of the outer ear
Pinna - sound collecting cone, many animals can move to aim
Eardrum/tympanic membrane - taut membrane vibrates from sound waves funnelled by pinna
Middle Ear
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)
Inner Ear
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)
Auditory Processing in the brain
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
Place theory
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
Frequency Theory
Pitch depends on frequency (rate) basilar membrane vibrates, whole membrane vibrates at once (drumhead)
Two cues to auditory localization
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
Reconciling Place and Frequency Theory
Both right, whole membrane moves, peaks at specific places depending on frequency
Human echolocation
Say “click click click” to judge sound distance bouncing off objects
Monaural and binaural cues
1 ear and 2 ears
