properties of the ear Flashcards
What are the three regions of the human ear?
Outer ear, middle ear, inner ear
What is the function of the pinna?
Captures and localises sounds
What is the approximate length of the ear canal?
About 2.5 cm long
What is the resonance frequency of the ear canal?
Lowest being ~3500 Hz
What separates the outer ear from the middle ear?
The eardrum
What are the three bones in the middle ear?
- Hammer
- Anvil
- Stirrup
What is the role of the ossicles?
Transmit vibrations from the eardrum to the oval window
Why are the ossicles necessary?
To overcome the impedance difference between air and cochlear fluid
What does impedance quantify?
The resistance of a system to be set into motion
What is the formula for impedance?
z = P/V
What is impedance matching?
The process of overcoming the impedance difference between air and cochlear fluid
What two factors contribute to impedance matching?
- Difference in areas of oval window and eardrum
- Lever action of the ossicles
What are hair cells in the cochlea responsible for?
Transmitting signals to the brain via the auditory nerve
What is the length of the auditory nerve?
About 3.5 mm long
What are the three parts of the cochlea?
- Scala vestibuli (SV)
- Scala media (SM)
- Scala tympani (ST)
What is the function of the basilar membrane?
Acts as a frequency analyser
How does the stiffness of the basilar membrane vary?
Stiffer closer to the oval window, more flexible closer to the helicotrema
What is the range of audible frequencies?
20 Hz — 20,000 Hz
What happens when sound waves arrive through the outer ear?
They set the eardrum into vibration
What is a critical band?
Regions of the basilar membrane excited together by close frequency tones
What is the critical band width below 500 Hz?
A region of ~100 Hz
What phenomenon occurs when the frequency difference of tones is decreased below a critical band?
Roughness (dissonance)
What is masking in auditory perception?
When a sound is inaudible due to the presence of a second sound
How can a loud note mask a soft note?
If the soft note is in the critical band of the loud note
