Section 1.2 Middle Ear Flashcards by Morariu Miruna

What is Natural Frequency?

The frequency at which a system will oscillate if disturbed by an external force.

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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

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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)

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Natural Frequency is determined by m________ and s______.

mass and stiffness

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What is friction?

Force resisting the relative motion of an object

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The input frequency __________ to the natural frequency will have the __________ output– frequency selectivity!

Closer
Higher

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What are the three components of impedance?

mass, stiffness and fiction (resistance) only the mass and stiffness are related to frequency.

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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.

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We can see that the stiffness component ____________ if frequency
were to __________.So,
larger frequency means smaller stiffness.

Xc = s/2.pi.f

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Acoustic impedance is how much _________ energy is ___ ___________

It’s how much sound energy is NOT ABSORBED

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Carpets absorb sound and it isn’t bouncing
off the walls (reverberating) like in a gym. So it has___________ impedance

Low impedance

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Sound waves through air bounce back at 99.9% off water. So water has _________ impedance

High impedance

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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

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What is the resonant frequency of the ear canal?

3200Hz

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What is the length of the ear canal?

2.6cm

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What is the width of the ear canal?

0.7 cm in diameter

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What is reactance?

The
contributions of mass and stiffness to impedance

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The object will vibrate differently in response to different frequencies of different signals, this is called:

frequency selectivity

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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

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Which is the biggest contributor of the EE in terms of dB amplitude and how much?

Meatus (canal)
15 dB

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In hearing, we want GOOD ____________ and GOOD __________ resolution. It is hard to do, but it is achieved by the ________

frequency selectivity temporal resolution
Cochlea

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A system that has better frequency selectivity has poorer________.

temporal resolution

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___ friction, light damping, vibration will last _______. (poorer temporal resolution)

Low longer

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___ friction, large damping, vibration will stop _________. (Better temporal resolution)

high
quickly

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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