Sound and Hearing

Question 1

what is sound?

Answer 1

• sound is produced when matter is acted upon
• vibration that propagates as an acoustic wave
• made up of amplitude (loudness) and frequency (pitch)

Question 2

what is amplitude?

Answer 2

• sound pressure level
• magnitude of sound (loudness)
• measured in decibels

Question 3

what is frequency?

Answer 3

• measured in hertz
• pitch is the frequency of waves in a given amount of time
• high pitch = high frequency

Question 4

what is the process of hearing (outer ear)?

Answer 4

AIR -> To Pinna -> to external auditory canal to Tympanic membrane (causing it vibrate)

Question 5

what is the process of hearing (middle ear)?

Answer 5

Ossicles (small bones) vibrate and their vibration acts to amplify the sound waves these are passed through stapes to oval window of cochlear

Question 6

what is the process of hearing (inner ear)?

Answer 6

Stapes footplate rocks in and out of cochlear and generates waves in the perilymph of the scala vestibuli. These travel up the cochlear duct. The waves cause waves in the scala media which has the organ of corti on it and hair cells in it – this is how these are stimulated

Question 7

what structures are located in the outer ear?

Answer 7

• pinna
• external auditory meatus
• tympatic membrane

Question 8

what structures are located in the middle ear?

Answer 8

• ossicles
• ligaments and muscles

Question 9

what structures are located in the inner ear?

Answer 9

• cochla
• auditory nerve

Question 10

what is the function of the external auditory meatus?

Answer 10

• resonator that amplifies certain pitches or frequencies of sound before they reach the TM
• its a small opening surrounded by cartilage

Question 11

what is the function of the tympatic membrane?

Answer 11

• sound energy hits the TM and causes it to vibrate
• cone of light thats a boundary between outer and middle ear

Question 12

what is the function of the ossicles?

Answer 12

• to amplify the sound energy applied to TM to the fluid in the cochlea
• inclued the malleus, incus and stapes (MIS)

Question 13

what is the auditory tube?

Answer 13

• 3.8cm tube runs from middle ear to nasopharynx
• opens occasionally to equalize the pressure in the middle ear

Question 14

what is the function of the bony labrynth?

Answer 14

• oval window (footbed of the stapes that moves fluid called perilymph)
• round window (perilymph exerts force on the round window causing it to bulge slightly

Question 15

what is the cochlea?

Answer 15

• filled with perilymph
• movement of perilymph leads to movement of basilar membrane
• movement of basilar membrane means hair cells bend which cause the action potential to be sent along the cochlea nerve

Question 16

what is auditory perception?

Answer 16

• ability to receive, identify and attach meaning to sounds

Question 17

what is conduction deafness?

Answer 17

• hampers sound conduction to the fluids of the inner ear
• e.g impacted earwax

Question 18

what is sensorineural deafness?

Answer 18

• damage to the neural structures at any point from the cochlear hair cells to auditory cortical cells

Question 19

what is tinnitus?

Answer 19

• Ringing or clicking sound in the ears in the absence of auditory
  stimuli – is disorder of the cochlear

Question 20

what is menieres syndrome?

Answer 20

• Entire labyrinth disorder (affects the cochlea and the semicircular
  canals) causing vertigo, nausea, and vomiting