Exam 2: 11 & 12 Flashcards
Sound
For the physical stimulus and a perceptual response
Physical Definition of sound
Sound is pressure changes in the air or other medium
Perceptual definition of sound
Sound is the experience we have when we her
“If a tree falls in the forest and no one is around to hear is there a sound”
Is there a sound ? yes. why?
If we are using a physical definition, because the following tree causes pressure changes whether or not someone is there to hear them
If a tree falls in the forest and no one is around to hear is there a sound”
Is there a sound? No. why?
If we are using the perceptual definition because if no one is in the forest there will be no experience
The piercing sound of the trumpet felt a room refers to what definition of sound
experience of sound aka sound perception
“The sound had a frequency of 1000 HZ” what is the definition of sound
Physical stimulus aka sound stimulus
What is it called when the movements or vibrations of an object has pressure changes in air water or any other elastic medium that can transmit vibrations
Sound stimulus
 when the diaphragm of the speaker moves out it pushes the surrounding air molecules together what is this process called
 compression which causes a slight increase in the density of molecules near the diaphragm. 
When the speaker diaphragm moves back in air molecules spread out to fill in the increase base what is this process called
Refraction. The decrease density of air molecules caused by refraction cause a slight decrease in air pressure
Speaker creates a pattern of alternating high and low pressure regions in the air is neighboring air molecules affect each other.
This pattern of air pressure changes which travels through the air at 340 m/s and through water at 1500 m/s
Sound wave
Think of a pebble dropping into is still full of water
As the ripple move outward from the pebble the water any particular place moves up and down the fact that the water does not move forward becomes obvious when you realize of the ripples would cause a toy boat to Bob up and down not to move outward. 
changes in air pressure occur in a pattern described by a mathematical function called a sine wave
Pure tones 
A person whistling or the high-pitched know it’s produced by flute or close to
Pure tones
Tuning forks which are designed to vibrate with a sign wave motion also produce
Pure tones
Vibration can be described by noting it’s number of cycles per second does a pressure changes repeat
Frequency
The size of the pressure change is called what
Amplitude
Hertz is the number of peaks per second/ frequency
Example from the board that had three peaks per second
Hertz has a perceptual dimension which is
Pitch
The volume of a sound is the
violence of the intensity of a sound (also known as
loudness or amplitude)
Pitch is what we
Perceive
The quality we describe as high and low think singing
Pitch
Volume is how tall the peak is
Loudness is the volume of a
Sound
Human hearing range
20 to 20,000 hertz
Audibility curve shows the threshold of hearing in relation to frequency
humans are most sensitive to 2,000 to 4,000 Hz.
Auditory response area: falls between the audibility curve and the threshold for feeling.
– It shows the range of response for human audition.
Equal loudness curves: determined by using a standard 1,000 Hz tone
Two dB levels are used: 40 and 80
Participants match the perceived loudness of all other tones to the 1,000 Hz standard. Resulting curves show that tones sound:
At almost equal loudness at 80 dB
Softer at 40 dB for high and low frequencies than the rest of the tones in the range
Threshold of feeling on graph db ( intensity) id the highest, what can this do to us
Cause ear damage, body vibration in club
Equal loudness curve
Conversation level
Audibility curve threshold
Threshold of hearing, cant hear below
all other perceptual aspects of a sound besides loudness, pitch, and duration
– It is closely related to the harmonics, attack, and decay of a tone.
Timbre
Effect of missing fundamental frequency
Removal of the first harmonic results in a sound with the same perceived pitch, but with a different timbre.
• This is called periodicity pitch.
The buildup of sound at the beginning of a tone
Attack of tones
Decrease in sound at end of tone
Decay of tone
Pinna and auditory canal are located in the
Outer ear
What does the pinna do
Help with sound location
Tube like structure 3cm long, protects the tympanic membrane at the end of the canal
Auditory canal
The resonant frequency of the canal amplifies frequencies between 1,000 and
5,000 Hz.
Auditory canal
Two cubic centimeter cavity separating inner from outer ear Contains the three ossicles
Middle ear
moves due to the vibration of the tympanic membrane
Malleus
transmits vibrations of malleus
Incus
transmits vibrations of incus to the inner ear via the oval window of the cochlea
Stapes
Functioning of ossicles
Outer and middle ear are full with air
The inner ear is filled with
Fluid that is much denser than air
Middle ear muscles dampen the ossicles’ vibrations to protect the inner ear from potentially damaging stimuli.
Three ossicles are filled with air what do they do?
Ossicles act to amplify the vibration for better transmission to the fluid 
Stapes transmit vibrations to the inner ear
Through window of cochlear
Fluid-filled snail-like structure (35 mm long) set into vibration by the stapes
Cochlea
The inner ear
Main structure for cochlea
Base of cochlear starts with
Very high frequency
Organ of corti is
Contained by cochlear partition
Ear drum vibrates making these three bones vibrate, what are they called?
Malleus, incus, stapes
The three small bones that vibrate from the ear drum do what
The malleus, the incus, and the stapes vibrate amplify/increase the sound vibration and send them to the cochlea.
The cochlea is shaped like a snail and is filled with liquid, why is this liquid important
The fluid in the cochlea is important because as the sound vibrates make the fluid ripple which creates waves, the silia rides the waves, that turns the movements into electrical signals. Ions rush to the top of the hair cells and fall down signaling neurotransmitters. The neurotransmitters move down and sit on the auditory nerve which travel to the brain.
The hair cells at the base of the cochlea detect
Higher pitched sounds like flute
The hair cells towards the top of the cochlea detect
Lower pitched sounds like a trombone
The very top of the cochlea, the hair cells detect
The lowest pitched sound like a tuba
The auditory nerve goes from cochlea to brain and we recognize these as
Sounds
High pitch sound waves are
Smaller and closer together
Low pitch sound waves are
Longer slow waves
How loud a sound registers depends on
The waves amplitude
The three smallest bones in the body
The ossicles, located in the middle ear. The malleus, incus, stapes
Also known as the hammer, set into vibration by the tympanic membrane
Malleus
The malice is sat into vibration by the tympanic membrane to which it is attached and transmits its vibration to the
Incus
Also known as the anvil, which transmits its vibration from the malleus
Incus
Transmits into vibration to the incus which in turn transmits its vibration, to the inner ear by pushing on the membrane covering the oval window
Stapes
Why are the occicles necessary?
The outer ear and middle ear or filled with air but the inner ear contains a watery liquid that as much denser than air.  The mismatch between the low density of the air and the high density of this liquid creates a problem. Kind of like it would be difficult to hear people talking to you if you were underwater and they were above the surface
The small scale toll muscles in the body these muscles are attached to the icicles in a very high sound levels the contract to dampen the ossicles vibration this reduces the transmission of low frequency sounds and helps to run intense low frequency components from interfering with our perception of high frequency
Middle ear muscles
The upper half of the cochlea call the scala vestibule in the lower half called a skeleton Pani for separated by a structure called
Cochlear partition
Inside the cochlea, There are two separate sections, what are these called
The two separate sections in side the cochlea are the organ of Corti Which contain the hair cells the receptors for hearing
 basilar membrane vibrates in response to sound and supports the
Organ of Corti
Cilia bend in response to movement of organ of Corti and the tectorial membrane
First step of transduction taking place
Yourselves band and cause transduction from vibration to neural signals
Bekesi place theory of hearing says
 frequency of sound is indicated by the place on the organ of Corti that has the highest firing rate
Békésy theorize that due to its placement along the cochlea each sensory cell (hair cell) responds maximally to a specific frequency of sound (tonoyopy)
Békésy temporal coding theory
Faze locking in volley theory multiple neurons groups of fibers represent the frequency
Signal generated in the hair cells of the cochlea are transmitted out of the cochlea and nerve fibers of the auditory nerve
Auditory nerve carries the signal is generated by the inner hair cells away from the cochlea long the auditory pathway eventually reaching the auditory
Auditory nerve fibers from the cochlea synopsis in the sequence of subcortical structures
Structures below the cerebral
The sequence begins with the cochlear nucleus and continues to the superior olivary nucleus in the brainstem the inferior colliculus and the midbrain and the medial geniculate nucleus in the thalamus
You’re walking down the street lost in thought Paying enough attention to avoid bumping into oncoming pedestrians suddenly you hear a screech breaks in a woman screaming you quickly turn to the right and see that no one was hurt but how did you know to turn to the right and where to look somehow you could tell where the sound is coming
This is sound localization
You’re sitting in a coffee shop talking with a friend but there are many other sounds as well other people talking nearby, Occasional screech of the espresso machine, music from speaker overhead, a car jams on his break outside. How are you can separate the sound your friend speaking from all the other sounds in the room?
Availability to separate each of the sound sources and separate them in space is achieved by a process called auditory system analysis well all this is going on you’re able to hear what your friend the same word by word intergroup her words together treat sentences this is perceptual grouping
In a coffee shop you hear each other sounds the music the talking in the mechanical fizzing sound is coming from different locations in space what do the sounds at different locations create
Auditory spaces which exist all around wherever there is sound
Locating of sound source is an auditory space is called
Auditory localization
Consider a tween bird and a meowing cat, The bird and the cat in visual information are in different relative locations The birds tweet tweet and the cats meow stimulate the cochlea Based on their sound frequencies and as we saw in chapter 11 these frequency cause patterns of neural firing that result in our perception of atones pitch in timbre
Activation of nerve fibers in the cochlea is based on
The tones frequency components and not on where the tones are coming from this means that two tones with the same frequencies that originate in different locations will activate the same hair cells and nerve fibers in the cochlea. 
The auditory system must therefore use information other than the place in the cochlea determine location this information takes the form of
Location cues
Created by the way sound interacts with the listeners head and ears
Location cues
What are two kinds of location cues
Binaural cues which depend on both ears and spectral cues which depend on just one ear
The azimuth 
Extends from left to right
Elevation
Which extends up and down
Distance of the sound source from the listener
Localization and distance is much less accurate then as a moose or elevation localization
Localization works best when the sound source is familiar or when Kuser available from room reflections. 
Use information reaching both ears determine the azimuth (left to right) of sounds
Binaural cues
The two binaural cues are
Interaural level difference and interaural time difference both are based on a comparison of the sound signals reaching the left and the right ears
Sounds that are off to the side or more intense at one year than the other and reach one ear before the
Interaural level difference
Is based on the difference in the sound level pressure or just level of the sound reaching the two ears. A difference in level between the two ears occurs because the head as a barrier that creates an acoustic shadow reducing the intensity of sound that reach the far ear
Consider a situation in which small ripples in the water are approaching the boat because the ripples are small compared to the boat they bounce off the side of the boat and go no further now imagine the same as ripples approaching the cattails because the difference between the ripples is large compared to the stems of the cattails the ripples are hardly disturbed and continue on their way
These two examples illustrate that an object has a large effect on the wave that is larger than the distance between the waves as occurs when short high frequency sounds hit the head but has a small effect if it’s smaller than a distance between the waves as occurs for a longer low frequency sound waves for this reason the ILD is an effective cue for location only for high frequency sounds
The other binaural cue, Interaural time difference Is the time difference between when is sound reaches the left here and when it reaches the right here
If the source is located off to the side and be the sound reaches the right ear before it reaches the left because the ITD becomes Larger a sound sources are located more to the side the magnitude of the ITD can be used as a cue to determine a sounds location
ITD is most effective for determining the locations of low frequency sounds and ILD is most effective for high frequency sounds so between them they cover the frequency range for hearing however because most sounds in the environment contain low-frequency components ITD is a dominant binaural cue for hearing
Say you are extending your hand directly in front of you at arms length and are holding a sound source because a source would be equal distance from your left to right ear the time and level difference would be zero if you now imagine moving your hands straight up equal distant from the two ears so both time and level differences are still zero
Because the time and level differences can be the same and a number of different elevations they cannot reliably indicate the elevation of the sound source
These places of and Ambiguity are illustrated by
The cone of confusion Any location that yields virtually the same intensity in time information will not be identifiable without head movement (cone of confusion)
Cues in which information For localization is contained in difference in the distribution or spectrum of frequencies that reach each year from different locations these differences are caused by the fact that before the sound stimulus enters the auditory canal and is reflected from the head and within the various folds of the pinnae
Spectral cues
The fact of spectral cues with the head and Pinay have been measured by placing small microphones inside a listeners ear and comparing frequencies from sounds that are coming from different directions
The Jeffress neural coincidence model
The Jeffries model of auditory localization proposes that neurons are wired so they each receive signals from the two ears. Signals from the left ear arrive along the blue axon and signals from the right ear arrive along the red axon. If the sound source is directly in front of the listener the sound reaches the left and right ear simultaneously and signals from the left and right your start out together.
As each signal travels along its axon it stimulates each neuron intern at the beginning of the journey neurons receive signals from only the left ear neurons 123 or the right ear neurons 987 but not both and they do not fire but when the signals both reach neuron five together that neuron fires
This neuron and the others only fire when both signals coincide by arriving at the neuron Simultaneously the firing of neurons five indicates that ITD = 0
The sound comes from the right the sound reaches the right ear first that gives a signal from the right ear a Headstart so that it travels all the way to neuron three before it meets up with the signal from the left ear. Neuron three detects IT D’s that occur when the sound is coming from a specific location on the right the other neurons in the circuit fire to locations corresponding to other IT D’s we can therefore all these coincidence detectors ITD to doctors since each one fires best to a particular ITD
The Jeffries model therefore proposes a circuit that contains a series of ITD detectors each tune to respond best to a specific ITD. According to this idea ITD will be indicated by Which ITD neurons firing this has been called a place code because I TD is indicated by the place which neuron where the activity
The ITD turning curves plot the neurons firing rate against the ITD recording from neurons in the brain stem of the barn owl which has excellent auditory localization Abilities has revealed narrow tuning curves that respond best to specific I TDs like the ones in figure 12 point
The result of research in which I TD tuning curves are recorded for mammals may appear at first glance to support the Jeffries model, 
And I TD tuning curve of a neuron in the gerbil superior olivary nucleus. This curve has a peek at an ITD of about 200 µs in drops off on either side however when we pot that I will curve on the same graph we can see that the gerbil curve is much broader than that I will curve in fact the gerbil curve is so broad that a peek says IT D’s far outside the range of ITDS that a gerbil woukd actually hear in nature
Because of the brightness of the ITD curves in mammals it has been proposed that coding for localization is based on broadly to neurons 
According to this idea they are broadly tuned Neurons in the right hemisphere that respond when sound is coming from the left and broadly to neurons in the left hemisphere that respond when sound is coming from the right. The location of a sound is indicated by relative responses of these two types of broadly tuned neurons
