Exam 3 Flashcards
What are some of the functions of sound? What does it provide that vision does not?
Sound allows greater awareness of the environemnt that is not directly in our visual field, can alert us to predators or to prey.
What are the 2 possible definitions of sound
Physical and perceptual definition
When a tree falls there is always the physical sound but not the perception
How is the sound stimulus described in terms of pressure changes in the air?
It is similar to the ripples of a puddle, the aactual particles move only a slight amount
What is a pure tone?
a pure tone is a tone with the wave form sine
Why was the decibel scale developed to measure amplitude, is decibel perceptual or physical?
Developed to shrink the large scale of possible sound amplitudes into better units based on log, decibel is physical measuring amp
What is a complex tone? harmonics? frequency spectra?
Complex tone are tones with multiple harmonics , they are periodic tones like pure tones but their harmonics make them different, the frequency spectra shows a way of indicating a a tones fundamental frequency
How does removing one or more harmonics from a complex toe affect the repition rate of the sound stimulus
it doesn’t effect it , the repetition is the same
What is the relationship between sound level and loudness?
level is the physical characteristic while loudness is the perceptual characteristic
What does the audibility curve show about physical characteristis and perceptual characteristics?
perception requires both the frequency and level to be in a certain range . some frequencies need less decibels to be heard while some need a higher level to be heard
What is Pitch in physical characteristics and what are the tone chroma
pitch can be understood as a change in fundamental frequency, Tone chroma is the same fundamental frequencies seperated by multiples of 2 , they create octaves
What are the structures of the outer ear
Pinnae, auditory canal and tympanic membrane,
The auditory canal reinforces frequencies at a resonant frequency , this amplifies frequencies between 1,000Hz and 5,000Hz
What are the stuctures and functions of the mid ear
Ossicles and oval window, the ossicles the malleus hits the incus and transmits to the stapes which at its footplate attaches to the oval window of the cochlea
What are the structures and functions of the inner ear
THe Innear is made up of the cochlea, the cochlea is filled with fluid and is separated by the organ of corti into the upper scala vestibuli and the lower scala tympani,
What causes the bending of cilia in hair cellls
Vibrations from the oval window move the organ of corti up and downand causes he tectorial membrane (stretches outer hair cells) side to side.
What happens when cilia bend
Inner hair cells, when bent in a certain direction, will fire because of tip links opening ion channels that cause a neurotransmitter release to the auditory nerve fiber
How does phase locking cause the electrical signal to follow the timing of the sound stimulus
because the vibration peak correlates with the moving of the cilia into a certain direction.
What did Bekesy discover about basiliar membrane vibration
It moves in a traveling wave and it is selective as it filters out certain vibration. high early, low later
What is the relationship between sound frequency and basilar membrane vibration
The place of maximum vibration changes its location on the basilar membrane with a change in Hz. low Hz close to apex , high hz close to base
What does it mean to say that the cochlea acts as a filter and how does it correlate with a tonotopic map and neural frequency tuning curves
The hair cells respond to certain frequencies better than others. the tonotpic and neural frequency tuning curve shows that some frequencies require a lower threshold to fire a neuron.
What is a neurons characteristic frequency
the frequency in which a neuron is most sensitive to
How do outer hair cells act as cochlear amplifiers and what was different about cochlear amplification in relation to Bekesy’s discoveries
Bekesy did not perform measurent on living cochlea so it turns out that outer hair cells don’t let ions flow across but elongate and contract in a way that moves the basilar membrane with it, this amplifies certain frequencies better than others.
Describe place theory
theory of pitch perception based on the relation between a sound’s frequency and the place along the basilar membrane this activated
How was place theory challenged by the effect of the missing fundamental? can it be modified to explain the effect
when the fundamental was removed the pitch did not change, the place where the peak would have been before is now different.
Modification: in a complex tone there will sill be vibration to the remaining harmonics, pitch can be taken from the pattern of places where vibration occurs
Burns Viemeister experiment and its implications
challenged even modified version of place theory by amplitude modulated noise.( noise is stimulus with many random frequencies and no vibration pattern , when level was fluctuated pitch was perceived)
