PSYCH 261- Audition and the Vestibular Sense

What is the physical stimulus of sound?

• it is the compression of air paritcles

• waves with high air pressure (particles closer together) at peaks, low air pressure (particles far apart) at dips

Amplitude of a sound wave:

• loudness of a sound

  • small wave quiet

  • tall wave loud

Frequency of sound waves:

• the pitch of a sound

  • small wave low

  • tall wave high

What sound is a simple wave?

• a pure tone

What sound is a combined complex wave?

• the sounds we frequently hear:

  • can be decomposed into individual tones

Why does a woofer speaker move?

• bc it is compressing the air next to it and pushing it in waves towards our ears, but sound does not travel very well

Complexity of a sound wave:

• the timbre of a sound:

  • what distinguishes the sound from others ie. a piano vs violin playing the same note

Pinna

• fleshy part of ear

Ossicles

• Three tiny bones that vibrate:

  • Malleus/Hammer

  • Incus/Anvil

  • Stapes/Stirrup

Cochlea

• inner ear

  • where the main processing is

  • Where the auditory nerves terminate

  • Snail-shaped region

Oval window

• membrane that is right on the cochlea

Round window

• another membrane window on the cochlea

Perilymph

• extracellular fluid

Vestibular Canal

• in the cochlea

• the scala vastibuli

• contains parilymph

Tympanic canal

• in the cochlea

• the scala tympani

• contains paralymph

Cochlear duct

• in the cochlea

• the scala media

• contains endolymph

Organ of Corti

• key area with neurons and receptors

• where transduction happens (pressure and movement → neural signals)

  • made up of:

    • tectorial membrane

    • inner/outer hair cells

    • nerve 8

    • Cilia

Cilia

the little fingers that protrude out of hair cells

Why do you sound different on video compared to when you’re speaking?

• you are only receiving signal from the auditory canal, missing the usual vibrations from your vocal chords

Process of sound entering the ear:

1. external sound enters AUDITORY CANAL

2. TYMPANIC MEMBRANE is vibrated by air particle movement (can also be vibrated by internal sound)

3. movement of tympanic membrane causes OSSICLES to vibrate

4. vibration of ossicles leads to movement of OVAL WINDOW

5. wave produced in the PARALYMPH of the VESTIBULAR CANAL

6. wave transfered to the PARALYMPH of the TYMPANIC CANAL

7. the BASILAR MEMBRANE is vibrated- which causes the organ of corti to be moving relative to ENDOLYMPH; NERVES START TO FIRE

8. ROUND WINDOW: pressure release valve

9. axons of AUDITORY NERVE leave the cochlea

What is the end result of sound entering the ear?

moving fluid via a wave within the ear to move against the cilia

Endolymph

• high in potassium

• low in soduim

• fluid that stimulates cilia

Tip Links

• protein fibres that connect cilia

How are cilia organized?

by height/length, they are all different heights

Spiral ganglion cell

• the auditory nerve

  • the connection of the cell to the auditory nerve