Sound transduction 1
This presentation is the property of its rightful owner.
Sponsored Links
1 / 16

Sound Transduction 1 PowerPoint PPT Presentation


  • 76 Views
  • Uploaded on
  • Presentation posted in: General

Sound Transduction 1. Or, if the a tree falls in a forest and no one is around does it still reflect light?. What is Resonance?. Resonance Characteristic frequency response Density & Tuning Sharpness Hi dense = Lo Sharpness Size/Cavity Breaking Glass Demo.

Download Presentation

Sound Transduction 1

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Sound Transduction 1

Or, if the a tree falls in a forest and no one is around does it still reflect light?


What is Resonance?

  • Resonance

    • Characteristic frequency response

      • Density & Tuning Sharpness

        • Hi dense = Lo Sharpness

      • Size/Cavity

    • Breaking Glass Demo


The Outer Ear: All about resonance

  • Pinna

    • Immobile cartilage side of head

  • Flange

    • ~3 - 4000 Hz resonance

  • Concha

    • ~1 – 7000 Hz resonance

  • Why such high frequencies?

    • Thoughts?

  • Directionality

    • Finger in folds demo

    • Spectral Filter (e.g., Rayker et al., 2004)

      • Resonance Frequencies

        • ~1000 – 7000 Hz

      • Notch Filter

        • ~ 700, 3500, 7000, 14000 Hz


  • Outer Ear: con’t

    • Meatus

      • Cartilaginous – bone

        • Density & Resonance

        • 3000 Hz resonator

      • Wax + Hair

        • Dirt Filter

    • Tympanic Membrane

      • Elastic Skin stretched across a bony ring

      • Stiff cone (2 mm height)

        • High Fidelity Transfer


    Middle Ear: The Saga Continues

    • The Impedance Problem

      • Getting sound to the sensors

    • Tympanic Membrane to Oval Window (stapedial footplate)

      • Orders of magnitude size difference

    • Ossicular chain

      • Malleus – Incus – Stapes – Stapedial Footplate

        • High density benefits!


    More middle ear goodness

    • Air filled pressure equal to outside

      • Eustacian Tube regulation

    • High intensity sound response

      • Multiple muscles

      • Sound attenuators


    Quick Interruption!

    • TLA 1: Hearing Under Water (HUW)

      • Why is this important?

      • Ingredients:

        • Sound source (Clicker?)

        • Still water (bath, sink, pool)

      • Stick your ear, or a friend’s ear under water

      • Make sound in air and under water and listen with:

        • Out of water ear

        • Under water ear

      • Questions: Which produces the loudest sound? Is it difficult to determine directionality?


    Into the Inner Ear

    • Major subdivisions of the Bony Labyrinth

      • Vestibular & Auditory

    • Auditory-side = Cochlea

    • Cochlea

      • Cavity within bone, Fluid-filled caverns

      • Curls like a snail


    Life in the Cochlea

    • Three major subdivisions

      • Scala Vestibuli: Largest cavity, filled with perilymph (e.g., Ricci & Fettiplace, 1998)

        • Positively charged Sodium Ions (Na+)

      • Scala Media: Smallest cavity, filled with endolymph (e.g., Ricci & Fettiplace, 1998)

        • More positively charged Potassium & Calcium Ions (K+, Ca++)

        • Where the action is!!!

      • Scala Tympani: Mid size cavity, filled with perilymph

        • Connected to Scala Vestibuli


    Scala Media, come get some!

    • ‘Organ of Corti’

    • Organ o’ Corti contains

      • Basilar Membrane (base)

      • Tectorial Membrane

      • Inner Hair Cells

      • Outer Hair Cells

    • Hair cells embedded in Bas. Membrane

    • Outer Hair Cells contact Tect. Membrane


    Basilar Membrane

    • Properties of the Basilar Membrane

      • Apex thin and stiff, Base broad and flexible

    • Standing Waves

      • Upward spread of masking

      • Why do higher Frequencies get masked by lower frequencies?


    Why does it matter that the Basilar Membrane moves?

    • Hair cell magic

    • Outer Hair Cells

      • ~ 12,000 in three rows

      • Afferent and Efferent connections

      • Attached to muscle fiber

    • Inner Hair Cells

      • ~ 3,000 in single row

      • Afferent connection

      • Passive Motion


    Actual Transduction!

    • Wave along Basilar Membrane

      • Causes inner hair cell shearing

      • Shearing opens channel

        • Endolymph in Scala Media attracts perilymph in Scala Tympani

        • Charges up Hair cell to cause neural firing


    What are the outer hair cells doing?

    • Outer Hair cells motile & embedded in Tectorial Membrane

      • Theory 1. Stiffen to attenuate sound along the basilar membrane, shear to add energy to the basilar membrane

      • Theory 2. Stiffen to raise the Tectorial membrane away from the inner hair cells, shear to lower the Tectorial membrane and obstruct the inner hair cells


    The big picture

    • Outer/Middle ear filter and intensify sound

    • Inner ear detects sound

      • Inner Hair Cell movement along the basilar membrane

        • Converts Mechanical energy to Electrical energy (nerve impulse)

      • Outer hair cells help modulate movement along the basilar membrane


    Questions?


  • Login