Unit 3.2 Flashcards
External Ear
- pinna & auditory canal
- crucial for sound localization
- filtering by pinnae is a monaural cue for localization
Binaural cues for localization
Interaural timing difference (ITD)
- ears are at different places on the head, so the time at which the hear the sound is different
- tells us where the sound is coming from
Interaural level difference (ILD)
- sound hits one ear, head creates a shadow so the other ear doesn’t perceive the sound directly
- perceives the sound at a lower level
Middle Ear
- tympanic membrane (eardrum) & ossicles
- 3 ossicles: malleus, incus, stapes
- eardrum vibrates - vibrations in the ossicles - move to inner ear
Goals of the middle ear
Impedance matching = preservation of energy across two media that differ in levels of resistance
- air (external ear) to fluid (inner ear)
- ossicles amplify
Keeps loud sounds out of the cochlea
Inner ear
Cochlea
Contains basilar membrane
- bands of hair cells
- two rows: inner and outer
- pitch detection
Transduction: physical wave - electro-chemical signal
Time theory
encoded according to the pattern of firing/timing on basilar membrane
- explains encoding of lower freq. and fails for freq. above 5,000Hz
Place theory
encoded based on the location the basilar membrane is excited
- explains encoding of higher freq. and fails for freq. below 50Hz
Critical bands
- bands of frequencies that the ear will respond similarly to, which affects consonance & dissonance
Mosquito teen repellant
exploits presbycusis - hearing loss associated with aging
Music induced hearing loss statistic
45% of undergraduates (in music) have detectable hearing loss
Cochlear Implants
- surgically implanted within the inner ear
- external sound processor placed behind the outer ear to stimulate the auditory nerve
