2: Audiology Flashcards
What produces sound?
Energy waves of particle displacement, both by compression (more dense) and rarefaction (less dense) within an elastic medium
What is the definition of amplitude in sound?
The maximum displacement of a vibrating particle of the medium from its mean position
What is the definition of intensity of a sound?
The amount of sound energy through an area per time, refers to sound strength or magnitude
What is the definition of sound pressure?
Sound force (related to acceleration) over a surface per unit time
What is the definition of sound frequency?
Number of cycles (complete oscillations) of a vibrating area per unit time, correlates with pitch
What range of frequencies is the human ear able to hear?
20Hz to 20,000 Hz
What is a single frequency sound called (rarely occurs in nature)
Pure tone
What is the name for aperiodic complex sound?
Noise
What is the term for the frequency at which a mass vibrates with the least amount of force?
What determines it?
Resonant frequency
Elasticity, mass, and the frictional characteristics of the medium
What is a decibel
logarithmic expression of the ratio of two intensities
What is sound pressure level (SPL) a measurement of?
Sound strength
What does zero dL HL represent
Average lowest intensity perceived by normal hears 50% of the time
**HL=hearing level
What does zero dB SL represent
Level of intensity at which an individual can just perceive a sound in 50% of presentations (threshold)
What are the components of the external ear?
Auricle
EAC
Outer portion of the TM
What is the average resonant frequency of the EAC?
2700 Hz
What determines the displacement of the ossicular chain?
Frequency and the intensity of the sound
At what range of frequencies does the TM and the ossicular chain most efficiently transmit sound?
500-3000 Hz (normal speech)
What are the four factors that allow for impedance matching in the middle ear?
Surface area of the TM vs that of the stapes
Lever action of the ossicular chain
Natural resonance and efficiency of the outer and middle ears
Phase difference between the oval and round windows
What is the difference between the SA of the TM vs that of the stapes footplate?
TM: 85-90 mm2, only 55mm2 vibrates
Stapes footplate: 3.2mm2
17:1 increase in energy by concentrating the area