Hearing Flashcards
How is sound caused?
by changes in air pressure
What is amplitude?
- decibels: dB
- related to loudness
What is frequency?
- Hertz: Hz
- related to pitch
What is a phase (in a pressure wave)?
the position within a cycle
What is a pure tone?
- sine wave
- simplest sound wave
What is Fourier analysis?
the process of decomposing complex sounds into their sine wave components
What is the lowest frequency component of a complex sound?
the fundamental
*What are many complex sounds made up of?
harmonics—integer multiples of the fundamental
What are the three main areas of the outer ear?
- Pinna
- External auditory canal
- Eardrum (tympanic membrane)
What is the function of the PInna (outer ear)?
- increases the sound amplitude
- helps determine the direction from which a sound is coming
What is the function of the external auditory canal (outer ear)?
- provides protection
- increase the sound amplitude
What is the function of the eardrum (outer ear)?
- vibrates in response to sound waves
- moves bones in the middle ear
What are the three bones (ossicles) of the middle ear?
Malleus
Incus
Stapes
What are the functions of the ossicles (middle ear)?
transmit vibration of the eardrum into the choclea through lever actions
What does the inner ear consist of?
semicircular canals - sense of orientation
cochlea
How does the cochlea (inner ear) work?
it is filled with liquid which moves in response to the vibrations coming from the middle ear
What are the three canals on the cochlea (inner ear)?
- Vestibular canal
- Tympanic canal
- Cochlear duct
What separates the canals of the cochlea (inner ear) and what is the function of the membrane?
basilar membrane
- converts vibrations into neuron signals
What is the central auditory pathway?
- nerve fibres from each cochlea synapse in a number of sites (nucleus’s) on the way to the primary auditory cortex
- input from both ears is present in both hemispheres
- seems that the cortex deals with more complex auditory tasks while the lower structures deal with simple aspects of sound (sound perception is beyond PAC)
How is the frequency of a sound processed in frequency coding?
- waves travel along the basilar membrane and peak at different points depending on the frequency of the sound
- the location of the peak identifies the frequency of the sound
How is the pitch of a sound processed in frequency coding?
simulating auditory nerves at different cochlea locations leads to the perception of sounds in different pitch
What happens if a fundamental is missing however the harmonics are present?
the missing fundamental is filled in
What are the two basic mechanisms for loudness perception and how does it work?
- overall firing rates
- range of firing
More neurons fire when a sound is more intense, each neuron fires more vigerously
ctors impact loudness?
- duration of sound (longer = louder)
- frequency (higher frequency = louder sound)
What occurs in the binaural process of auditory space perception?
interaural time difference
- onset difference
- phase difference
interaural intensity difference
What is the onset difference in the interaural time difference?
Unless a sound is directly in front of or behind you, it reaches two ears at different times
What is the phase difference in the interaural time difference?
The same sound will most likely be in different phases when it reaches each of the two ears
What is Interaural intensity difference?
- The same sound should be a bit more intense at an ear that is closer to the sound source
- The energy of a sound decreases as it travels farther
- The head works as a barrier that reduces the intensity of the sounds (sound shadow)
What is the Interaural time difference useful for?
localizing low-frequency sounds
What is Interaural intensity difference useful for?
localizing high-frequency sounds
What direction are we better at percieving?
- Humans perceive horizontal directions better than vertical directions through auditory cues
What are the two cues for auditory distance perception?
○ Loudness cues can tell us only about relative distance
○ Reverberation cues vary depending on various properties of the reflection surface
