summary Flashcards
(41 cards)
two main areas of hearing science
- physiological acoustics
- The study of the function of structures within an organism that are involved in hearing
applications
- The effects of prescription drugs on hearing
- The design of a replacement cochlea - psychoacoustics
- The relation between sound and how it is perceived
applications
- Examining infant hearing
- processing limitations of persons with hearing loss
- high quality music properties
- Examining theories of learning and detection
Why is the transfer function higher frequencies for infants than for adults
Because the structures of the infants hearing mechanisms are smaller and therefore they boost higher frequency sounds more
What functional subdivisions of the ear are linear and what does that mean
middle ear and outer ear are linear (no distortion, can predict complex tones based on pure tones)
middle ear = nonlinear
What are combination tones
cubic difference tones or distortion products that you can hear
What are simple difference tones (include equation)
f2-f1
tones that occur for real high levels of presentation
what are cubic difference tones (include equation)
2f1-f2
occurs for low levels of presentation
OHCs generate it
used to assess newborn hearing
Azimuth
horizontal direction expressed as the angular distance between a fixed point and the direction of an object
What are the three air filled spaces comprising the middle ear
tympanic cavity
epitympanic recess
mastoid air cells
What is the composition of the tympanic membrane
pars tensa
- 3 layers
- outer layer: skin
- middle layer: dense fibers
- medial layer: mucous lining
pars flaccida
- upper portion of the TM
only 3% of area
3 scala of the cochlea
scala vestibuli
scala media
scala tympani
what are the physical characteristics of the basilar membrane
apex = thin, bendy (low frequencies)
base = thick, stiff (high frequencies)
paradoxical traveling wave
What does it mean that the basilar membrane is a paradoxical traveling wave
if you stimulate the apical end, the basal end still moves first
click stimuli stimulates the whole cochlea at the same time, apical end is slower to respond so the basal end moves first
What are the physical characteristics of the hair cells
OHC = 3 layers, W or V formation of stereocilia, motility
IHC = 1 layer, U formation of stereocilia, no motility
What is OHC motility?
the ability of an organism to move independently using metabolic energy
allows them to emit their own sound
What are cochlear resting potentials (and the two kinds)
two voltages that are present even when sound isn’t being presented
type 1: endocochlear potentials: extracellular
type 2: hair cell potentials: intracellular
What is the total voltage gradient between the EC and HC potential
160 mV
What are stimulus related cochlear potentials (types)
cochlear microphonic
- mimics the input stimulus
summating potential
- DC potential
- shifts everything in one direction
- important for diagnosis of Meniere’s disease (people have an abnormally large summating potential)
What are compound action potentials or whole nerve potentials
neurons firing when they are stimulated
What is the Davis Battery Model of the cochlea
explains that a flashlight needs two batteries (just like there are two cochlear potentials)
need both batteries (cochlear potential) for the flashlight (cochlea) to work
the batteries have a resting potential (like the cochlear resting potentials) that are waiting to be used until the flashlight is turned on (waiting for a sound to stimulate the cochlea so they can create the stimulus potentials)
Radial fibers
type of afferent fiber
- comprise 85-95% of the total number of afferent fibers
innervate IHC exclusively
20:1 IHC ratio
responsible for carrying info about sound to the brain
Outer spiral fibers
type of afferent fiber
- comprise 5-15% of remaining fibers
innervate OHC exclusively
unmyelinated, skinny, and slow conducting
1:10 ratio
unknown function
What is prestin?
a protein that is found in the OHCs, which is evidence for their motility
Outer ear primary function
- protect middle ear
- provide gains for high frequencies
- assist in sound localization
primary function of middle ear
transduce acoustic energy into mechanical energy
