Audition Flashcards
Auditory Mechanisms in Diff Species
Species vary in the range of frequencies they can detect
Basilar Membrane
- Contains hearing receptors
- Varies in length across species
- Longer = wider range of frequencies (mammals have longest)
- Widens towards apex
Stimulus - Sound Waves
- Vibrations in air particles
- Condensed bands of air particles ripple away from sound source
- Needs a sound source
- Sound travels faster in liquids and solids
Sound waves are ______
Longitudinal (vibrate parallel)
Amp, Wavelength, Purity
Amplitude = Loudness (high amp, louder)
Wavelength = Pitch (short = high pitch, long = low pitch)
Purity = Timbre
External Ear
Changes Air Pressure
Pinna
Cone-shaped protuberances on the side of your head
- Collect sound waves, directs them into ear canal
Ear Canal
Narrowing tube in the outer ear that connects the outside world to the middle ear in the tympanic membrane
- Amplifies sound waves
Tympanic Membrane
thin membrane vibrating at the end of the ear canal
- Separates outer and middle ear
Ossicles
Stirrup, anvil, hammer
- Amplifies sounds
Where does air pressure get converted to soundwaves
fluid filled inner ear
Inner Ear
Detect change in fluid pressure
Cochlea
Connected to oval
- contains neural tissue for transferring changes in fluid motion to neural impulses
Oval window
small opening in side of cochlea
Vibrations in Basilar Membrane
Low frequency sound = long wavelength = ending near apex of the membrane
High frequency sound = small wavelength = one cycle will end near the base
Hair Cells
When hair cells are displaced by vibration, they convert the frequency of sound into electrical signal
Electrical signal in hair cells
Mechanical displacement of hair cells = (+) ions from extracellular fluid enter body of cell
- Loudness affects bending, # of (+) ions in neuron
- Rush of (+) ions reach threshold, cell depolarizes = AP
Outer Hair cells
- More numerous 4:1
- Fewer connections to brain
- Share one direct link to brain with 30 other outer hair cells
- Amplify sound
- Unmyelinated
Inner Hair Cells
Less numerous 1:4
- More connections to brain; 20
- Send pitch information
- Myelinated
Auditory Localization
Depends on interaural differences between ears
Interaural Time Difference
Changes depending on direction of incoming sound
- Specific neurons in superior olivary complex respond
Head Shadow Effect
If wavelength is larger than diameter of listeners head; soundwave can diffract around the head without losing intensity
What sound frequency does not cast a shadow
low
Superior Olivary Complex
respond to intensity differences from each ear
What would make it hard to locate sound
If it’s directly in front or behind you
Interaural Intensity Difference
Auditory cue resulted from a difference in sound intensity bw ears
Echolocation
where a receiver emits sound pulses and analyses the returning echo; forming a perceptual image of objects in the environment
Co-evolution
Process by which evolution and adaptation of traits of one species can directly affect the evolution of traits in other species
Absolute Pitch
ability to identify a pitch without reference to an external source
