Section 1.2 Middle Ear Flashcards
What is Natural Frequency?
The frequency at which a system will oscillate if disturbed by an external force.
Explain the relationship between a input, system, output and gain. (draw it)
input is processed by a system, resulting in a difference between input and output
Gain = change (difference) of signal amplitude and varies with frequency response
What is Frequency Response?
Measures of how gain is changed with frequency, gain as the function of frequency (the effect of an object on the frequency balance of signals passing through it)
Natural Frequency is determined by m________ and s______.
mass and stiffness
What is friction?
Force resisting the relative motion of an object
The input frequency __________ to the natural frequency will have the __________ output– frequency selectivity!
Closer
Higher
What are the three components of impedance?
mass, stiffness and fiction (resistance) only the mass and stiffness are related to frequency.
What can we see from this equation?
Xm= 2.pi.f.m
We can see that the mass component increases
with frequency Mass itself (m) is fixed in each system. So larger frequency, larger mass component.
We can see that the stiffness component ____________ if frequency
were to __________.So,
larger frequency means smaller stiffness.
Xc = s/2.pi.f
Acoustic impedance is how much _________ energy is ___ ___________
It’s how much sound energy is NOT ABSORBED
Carpets absorb sound and it isn’t bouncing
off the walls (reverberating) like in a gym. So it has___________ impedance
Low impedance
Sound waves through air bounce back at 99.9% off water. So water has _________ impedance
High impedance
Consider the middle ear. Sound is absorbed when it goes from the ear canal and the ossicular
chain is set in motion: __________impedance means that a lot of that sound is ___________.
low
absorbed
What is the resonant frequency of the ear canal?
3200Hz
What is the length of the ear canal?
2.6cm
What is the width of the ear canal?
0.7 cm in diameter
What is reactance?
The
contributions of mass and stiffness to impedance
The object will vibrate differently in response to different frequencies of different signals, this is called:
frequency selectivity
True or false: Even if the signal is not at natural frequency of a system, it can still vibrate.
True, just not at max amplitude
Which is the biggest contributor of the EE in terms of dB amplitude and how much?
Meatus (canal)
15 dB
In hearing, we want GOOD ____________ and GOOD __________ resolution. It is hard to do, but it is achieved by the ________
frequency selectivity temporal resolution
Cochlea
A system that has better frequency selectivity has poorer________.
temporal resolution
___ friction, light damping, vibration will last _______. (poorer temporal resolution)
Low longer
___ friction, large damping, vibration will stop _________. (Better temporal resolution)
high
quickly
What causes an object to vibrate? What varies about each object?
Vibrate in response to a driving force with various frequencies, their natural frequencies vary though.
What is frequency selectivity? (related to input/output)
The input frequency closer to the nat. frequency will have higher output (frequency selectivity)
d) When pushing a swing, what will not affect the frequency and what are the factors that will?
The way you push the swing will not affect the frequency of the swing, only the length of the rope and the mass of the girl
How do each of components of impedance relate to frequency?
Mass increases with frequency
Stiffness decreases with frequency
Resistance does not change with frequency
According the the reactance graph, which components are in opposing phases? (180 degrees)
Mass and stiffness
Describe frequency selectivity in one sentence.
The object will vibrate differently in response to different frequencies of signal but more to its natural frequency
What is damping?
Light damping, less absorption thus more vibrations
Large damping, more absorption thus more vibrations
What is the friction effect as it relates to damping?
Low friction, light damping, vibration will last long time (not stop quickly), this is poorer temporal resolution
High friction, large damping, vibration stop quickly, better temporal resolution
d) What is the friction effect as it relates to BOTH damping and frequency selectivity?
Low friction—smaller damping, narrow frequency response (better frequency selectivity)
High friction—larger damping, broader frequency response (poorer frequency selectivity
a) What is the general ratio measured by gain?
Output/input
Explain how the external ear acts like a tube in relation to resonant frequency (one sentence, brief)?
When air particles are vibrated by sound of various frequencies, the greatest amplitude is seen at the resonant/natural frequency.
How
would the frequency response be measured for the canal? For the concha?
, we compare two measurements: one is for input and the other is for output. For example, M1 is the measurement of input to Flange, M2 is the output of Flange, or the input to Concha. At any frequency, input/output gives gain. Frequency-gain relationship is frequency response.
The external ear resonance is based on the average of gain of which three parts?
Meatus, Concha and flange
Which of the three parts responsible for EE resonance the largest contributor to the overall gain?
Meatus
What is the overall gain at the average ear canal resonance?
15 dB
Which of the three parts responsible for EE resonance has a peak at lower frequency relative to the others?
Meatus has a peak at lower frequency
Which of the three parts responsible for EE resonance has a peak at higher frequency relative to the others?
Concha has a higher frequency peak
e) What is the approximate resonance frequency of the whole external ear?
3200Hz
f) How does resonant frequency change with age?
Higher resonant frequency at a younger age and 37 months closer to adult frequency, because of lengths of the canal
What is the second function of the external ear canal?
Provide cues for localization
What are two categories of EE localization cues cues?
Spectrum cues due to the transfer of function of the EE
Differences in signals received by the two ears (binaural cues)
What term is transfer function f similar to?
Frequency Response
What is another name for the pinna effect?
Pinna cues
a) What are the three ways the external ear protects the eardrum?
Irregular shape (S configuration)
ceruminous (wax)
Hairs
\What are three ‘protective’ components inside the ear canal? What fraction of the ear canal has these (laterally/medially)?
Outer 1/3 of the canal has hairs, sebaceous (oil) and ceruminous (wax) glands
c) How many degrees is the tympanic membrane angled with reference to the axis of the canal? What purpose does this serve?
45 degrees with the axis of the canal, reducing the impact of hitting by a foreign body
What is the self-cleaning mechanism of the ear canal
The slow growth of cells and the migration of them push debris out of the ear canal.
Epidermal migration produces “wrinkles
What is another name for the eardrum?
Tympanic Membrane
What is the (general) definition of a ligament?
Ligaments are elastic tissue which connect bones to other bones.
How many ligaments are/is there connected to the malleus? What are/is they/it?
3: Superior, lateral, anterior.
How many ligaments are/is there connected to the incus? What are/is they/it?
1: Posterior
How many ligaments are/is there connected to the stapes? What are/is they/it?
1: Annular ligament
What does the manubrium attach to?
The TM—umbo
Describe the rotation of the eardrum in relation to the bone chain.
- Lever like motion between malleus and incus connection
- Malleus and incus are rotated around its pivot, causing the eardrum to vibrate unevenly
- The largest vibration is on the inferior part of the eardrum
What are the four main parts included in the malleus
Head, neck, lateral process, manubrium
What are the 4 main parts in the incus?
Body, short process, long process, lenticular process
What are the four main parts of the stapes?
Head, neck, anterior/posterior crus, footplate.
What is one technique to tell which ear it is based on the tympanic membrane?
Either looking at the cone of light or the long process of the incus
What is the more known nerve that the chorda tympani is part of? What is its main role?
Facial nerve. The role of the chorda tympani is to carry taste from the ipsilateral half (same side) of the tongue.
What does ‘manubrium’ mean?
Handle Lateral part of the Malleus
How many layers do the pars flaccida and pars tensa have?
Pars flaccida: two layers (no fibrous layer). Pars tensa: Three layers
Flaccida vs. Tensa What purpose does one not having the fibrous layer serve?
The pars flaccida is more flexible and serves as an air pressure buffer.
Note: It does not attach to the bone chain and is therefore NOT responsible for sound conduction.
Flaccida vs. Tensa Describe the tenseness of one relative to the other?
The pars tensa is stiffer.
Flaccida vs. Tensa which one is thicker?
The pars flaccida.
Flaccida vs Tensa Which one is dorsal to the other? What is at the border between the pars tensa and pars flaccida (which nerve and which ligament)?
Pars flaccida is dorsal. Annular ligament and chorda tympani (a branch of the facial nerve) are at the border between the pars tens and pars flaccida.
Which view (medial or lateral) can we see the two parts of the eardrum?
Lateral
What is the self-cleaning mechanism of the ear canal?
Epidermal migration—the slow growth of cells and the migration of them push debris out of the ear canal.
What shape is the ear drum and which side does it tilt to?
concave and tilts 45 degrees from its top laterally
Which part of the malleus separates the pars flaccida from the pars tensa?
Lateral Process
How many layers is the ear drum made of?
4 layers
How long is the ET?
3.5 cm
Which ossicular bone is the largest?
The malleus
What is the formula of impedance?
What is part of the posterior (mastoid) wall of the tympanic cavity? (4)
Aditus antrum
stapedius muscle (pyramidal eminence)
Incudal fossa: indention in bone for the incus
Chorda tympani nerve entrance: branch of CN7
What is part of the Medial (labyrinthine) wall (5)?
Round window
Oval window (covered by stapes footplate)
Facial nerve canal
Prominence of lateral semicircular canal
Cochlear promontory
What is part of the Superior (tegmental) wall? (1)
Epitympanic recess or attic provides space for heads of malleus and incus
What is part of the Inferior (tympanic) wall?
Separates ME from jugular bulb below
What is part of the Lateral (membranous) wall?
Tympanic membrane
What is part of the Anterior Wall? (3)
Tensor tympani tendon/muscle entrance
Eustachian tube orifice (opening)
Internal carotid canal
