Tut 7 Completly done Flashcards
Definition of sound (physical and perceptual )
Physical: Sound is pressure changes in the air do to vibrations
Perceptual: Sound is our experience when we hear.
How do we change pressure ?
Due to consideration and rarefaction.
What is consideration ?
Vibrations which pushes air molecules together which leads to an increase in air pressure.
What is rarefaction ?
Air molecules move back out (seperate again)
- Decrease in air pressure
How does sound energy travel ?
Trough out waves
- Transverse (up and down) and
- longitudinal(back and forth) waves
- > Not really common
What is a sine wave ?
A pure tone (one wave)
Tell the structure of a complex tone:
- A complex tone is divided in a one fundamental frequency (lowest tone or base)
- Partial top layers
- Mostly they are harmonics of the fundamental frequencys (muliplies of FF)
A sound wave is made up off 2 parts:
- Amplitude
- Frequency
What is amplitude ?
Size of pressure changes (How far waves goes up and down)
- Also called intesity so how loud
- Meassured in DB (logorith function not proportional)
- 6 DB seem to be doubling the amount of loudness
What is frequency ?
Number of times per second in which the sound waves repeats
- Meassured in Hz
- 1Hz = 1 cycle per second
- The higher the pitch the higher the frequency
- we can perceive frequency till 20000 Hz
Define Fourier analysis
its a sinus function which divides a complex tone into many simple sin waves (frequencys) - which is needed for simplification - shown as a single line in a Diagramm - that is what the cochlear does for us.
structure of the outer ear ?
- sound waves pass trough the pinna
- then it passes trough the auditory canal
- which then reaches the tympanic membrane which starts to vibrate
What is the pinna ?
Outer structure of the ear which is good for object location
What is the auditory canal good for?
-For protection of the middle ear
What is the function of the tympanic membrane ?
Receives sound and transmit it.
Structure of the middle ear ?
formed by 3 ossicles
- Maleus (gets set into vibration)
- Incus (transmits vibration
- Stapes (pushing the oval window to transmit the signal)
- All of them increase the sound pressure
Structure of the inner ear ?
- Cochlea snai like structure
- only part with liquid
- when stapes moves against the oval window liquid is set into vibration
- has an tonotopic organization high frequencies at the beginning
What is an tonotopic organization ?
- goes from high to low Hz
- so as farther the liquid goes the lower the Hz
What is the actual sound procedure ?
- Stapes creates movement of liquid
- Cochlear partition moves which sets structure such as basilar membrane in movement
- movement against tectorial membrane leads to bending of hair cells
- movement of hair cells in one dircetion leads to the opening channel
- Ions can flow into the hair cells (afferent and effernt) and transmitter are released.
Define what phase locking is:
Neurons fire in synchrony with the auditory stimuli
- Till 1000 Hz
Define what volley locking is:
If neurons can not keep up with the frequency:
- Group of neurons are combined to still work in synchrony with the auditory stimuli (4000Hz)
- Its due to relaxation time of neurons
Name the sonicmg pathway:
- it is the pathway from cochlea to cortex
- goes from:
1. cochlear nucleus
2. Superior olivary nuclei
3. inferior colliculus
4. Medial Geniculate nucleus
5. Primary auditory cortex - vision has less stages only optic nerve
Name the parts of the auditory cortex:
- it lays under the temporal lobe
- it is hierarchical organized
- Corea area
(simple tones) - belt area (complex sound)
-parabelt area (most complex sound and combines information with other senses
Define the where (dorsal) pathways:
- After sonicmg
Good for locating sound
- Start behind parts of the core and belt area and goes to prefrontal cortex
Define the what (ventral) pathway
- after sonicmg
Identifying sound in general
- Starts infront of the core and belt area and goes to the prefrontal cortex
What is conductive hearing loss ?
- Damage on the outer middle ear but cochlea is still intact
- Basicaly sound does not reach the receptors (hair cells) no action potential
- everything is quite
- solution hearing aid
What is Sensorineural hearing loss ?
Inner ear problems
- Destruction of hair cells due to loud noise
- Treat is cochlear implant which translates sound energy into nerve impulses
What types of hearing loses do we have ?
- Conductive hearing loss
- Sensorineural hearing loss
- Hidden hearing loss:
What is hidden hearing loss ?
Loud noise leads to damage on the ear nerve cells
- Which are the connection between cochlea and brain
- its often under diagnosed because they can hear quite and loud frequencys but not with background noises
How is a cochlear implant structured ?
- microphone on the extrernal ear
- speech processor converts the sounds into digital signals and sends it to the internal implant
- internal implant converts signals into electrical energy
- electrical energy go to the injected electrodes in the cochlea
- the electrodes bypass the damaged hair cells and stimulate the auditory nerve fibers
What if a cochlear implant does not work ?
- Auditory nerves are destroyed
- We need: Auditory brainstem implants (ABIs) that bypass nerve fibers
- They directly stimulate the ventral cochlear nucleus
What does the audibility curve do ?
- Plots the relationship between intensity and frequency
- Also identifies tresholds of hearing (Low dB and high frequencies)
- Shows the perfect sound to be perceived regarding aplitude lvk and frequencys.
What is frequency coding? (How to endcode fequencies)
Place coding:
- higher frequency = more vibration on the base of basilar membrane
- less frequency more vibration on the apex Tonotopy
- We have to mirror tonotopy structure
And also time coding/temporal coding:
What are harmonics:
Multiple Hz of fundamnetal frequency.
How is doubling the sound pressure perceived:
- 6 db for physical
- 10 db for perceived loudness
What does the inner hair cells do:
They have a long and a short hair (called cilia) on hair cells, which are connected via a (rope) when long hair cell bends then the connection point on the short hair where rope is connected open the channels.
What does the outer hair cells do:
- monulate action potentail
- sharpen the procces
What is auditory maksing (pure tone):
- Overlaping tone of sound
- The mask of a tone strongest from low to high.
- relationship between mask and tone
What does turnning curve show:
- Neurons have specialized preferrention.
