Inner Ear 2... (Filters, Active process) Flashcards Preview

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Flashcards in Inner Ear 2... (Filters, Active process) Deck (25)
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1
Q

Envelope

A
  • the point along the basilar membrane that is frequency-selective
  • has to do w/ resonant properties
  • corresponds to peak displacement
2
Q

Travelling wave

A
  • tail is shallow and long
  • wavefront is steep and short
  • upward spread of masking
3
Q

Upward Spread of Masking

A
  • if you take a low freq sound and make it louder, it increases the envelope of the BM closer to the start, and can mask a higher freq signal that is softer
    E.g.
  • high intensity, Low Hz, masks High Hz
  • High Hz doesn’t mask low Hz, no matter the intensity
  • if you have high intensity, Low Hz, it will travel all the way to the apex
4
Q

4 Types of Filters

A
  1. Low pass
  2. High pass
  3. Band pass
  4. Band reject
5
Q

Low pass filter

A
  • passes low freqs thru

- attenuates high freqs

6
Q

High pass filter

A
  • passes high freqs thru

- attenuates low freqs

7
Q

Band pass filter

A
  • combines low and high pass filters
  • passes freqs within a certain range
  • attenuates freqs outside that range
8
Q

Band reject filter

A
  • passes most freqs
  • attenuates those in a specific range to very low levels
  • opposite of band pass
9
Q

Filter skirt

A
  • the slope of a band pass
  • steep slope = anything digital can be cut off
  • gradual slope = required by analog filter
10
Q

Cochlea acts as a _____

A

Bank of band-pass filters

- if we put a signal in, the envelop acts as a band-pass filter

11
Q

Von Bekesy’s opinion on BM Vibration

A
  • linear, related to gain

- whatever you put in, you get a predictable, fixed amount out

12
Q

Rhode’s opinion on BM vibration

A
  • nonlinear, more gain for less input
13
Q

Why the difference in opinion btwn VB and Rhodes?

A
  • VB used cadavers

- Rhodes used live animals

14
Q

BM Input/Output Function

A
  • 9000 Hz Characteristic frequency (Cf)
  • BM nonlinear near cf (true around freq of stimulating signal)
  • linear far from cf (1000 Hz)
15
Q

Critical Band

A
  • measure threshold to pure tone w/o masker
  • add noise masker
  • threshold goes up
  • cut out a notch of noise
  • as the notch widens, the threshold will start to come back down
  • when the threshold no longer decreases, the width of the notch = the width of the auditory filter for that sound
  • this is how we know auditory filters are a real thing!
16
Q

The _____ of the filter is a function of the ______ of the ear

A

The WIDTH of the filter is a function of the HEALTH of the ear

  • impaired ears have broader filters (too many other sounds trying to get in when listening… masks the signal they’re trying to hear)
17
Q

The active process involves 3 things:

A

OHCs
IHCs
Shearing of hair cells

18
Q

OHCs role in the active process

A
  • amplify sounds below 50 dB SPL
  • sharpen travelling wave peak
  • do not do the hearing, they do the CONDUCTION
  • efferent fibres (receive messages FROM the brain)
19
Q

OHCs ________ in response to sound

A
  • stretch and shrink!
20
Q

OHCs innervated by _______

A
  • olivocochlear bundle
21
Q

Evidence of the OHC active process

A
  • tuning curve
22
Q

IHCs role in the active process

A
  • without IHCs we have no hearing = signals will not be transmitted to the brain
    (afferent fibres)
  • cannot pick up sounds below 50 dB SPL
23
Q

IHCs innervated by _____

A

CN VIII (vestibulocochlear)

24
Q

Shearing of hair cells

A
  • cell responds to a tip deflection, less than the diameter of a hydrogen atom!
  • equivalent to a movement that would displace the peak of the Eiffel tower by 1cm
25
Q

Effects of this Active Process

A

Large dynamic response range

  • > low intensity sounds amplified
  • > above 20 dBSPL, amount of amplification declines until 90 dBSPL
  • > above 90 dBSPL, no additional amplification occurs (BM & IHCs are on their own)
  • > if you didn’t have OHCs you wouldnt hear anything soft

Generation of sound w/in cochlea

  • > spontaneous otoacoustic emissions (SOAE)
  • > evoked otoacoustic emissions (EOAE)
  • —> if you don’t have these, your OHCs aren’t moving