Hearing + Ear (I) Flashcards
What is sound
A longitudinal pressure wave travelling through air or a medium
Which 2 characteristics make up sound
Frequency (pitch)
Amplitude (intensity/loudness)
How do you work out frequency
1/t
T = period between sounds
What would high frequency t be
Smaller intervals between sound
What would increase in pressure cause for intensity
Increased pressure increases intensity of sound
Does t change measuring intensity
No. Period of sound is same
How do you work out intensity of sound (decibels) from pressure (pa)
20 log (pa/20)
20 is a reference level
Why is 20pa pressure only 0 decibels
Intensity measured in log
Log 20 (20/20) = 0
Is frequency dependent on pressure
Not always, we can detect a high frequency even at lower pressures
at what frequency pitch does intensity need to be highest
At high and low frequencies
What makes up the outer ear
Pinna
Which part of ear allows detection of sound externally and also on all vertical plates (ie left right up down)
Pinna outer ear
Which part of ear conducts sound to middle ear from the pinna
Ear canal
What does the ear canal allow and why
Amplification / increase intensity of sound due to its resonance
Where does the outer ear terminate
Tympanic membrane
What allows equal pressure on either sides of tympanic membrane allowing sound / vibrations
Eustachian tube opening (not open in air flights = no pressure equilibrium)
What makes up the middle ear
Ossicles
Malleus , incus and stapes foot plate
Which part of the middle ear is the longest
Malleus
What are the inner ear ossicles for
Transfer of vibrations to the cochlea via the stapes foot plate
How is the stapes foot plate attached to the cochlea
Via the cochlea oval window
Middle ear allows sound waves to travel from air to liquid cochlea. What is this called
An impedance transformer
Why is there increased pressure at the stapes than at the tympanic membrane (overcoming gas to liquid)
Tympanic membrane has a larger area
But both stapes and TM have the same force applied (stapes lower area so more force in a smaller area = higher pressure )
Pressure = force / area
By how much is pressure increases in stapes
X 18
Why is the fact malleus is longer than incus a way to affect pressure and therefore gas liquid barrier
Acts as a lever
When force is applied to malleus this increases force of incus acting on stapes
