Lesson 6 Flashcards
What allows attenuation to occur? (3)
- Absorption
- Reflecting
- Scattering
What is absorption?
The transfer of sound to heat
What makes up an image? (2)
- Reflecting
2. Scattering
What does 0dB mean?
You cant hear anything
What happens as decibels get higher?
It gets louder
What does 3dB mean?
2x
What does 10dB mean?
10x
What is the unit for attenuation?
Decibels
- dB
What do decibels describe?
The relationship between various measured sound levels
What is the formula for attenuation?
a = ac x L a = attenuation ac = attenuation coefficient L = length traveled
Attenuation coefficient
Attenuation that occurs with each cm the sound travels
What is the unit for attenuation coefficient?
dB/cm
What is attenuation depend on? (3)
- Type of tissue
- Length/distance of travel
- Frequency
What does it mean when your image is more fuzzy?
Less sound is traveling through
How much sound goes through bone?
None
What structures have high attenuation? (4)
- Bone
- Stomach
- Lungs
- Fatty liver
What structures have low attenuation? (2)
- Normal liver
2. Bladder
What is ac in soft tissues?
Half of the frequency
- 0.5 x freq. x length
What happens to attenuation if frequency increases?
It increases
What happens to attenuation if distance increases?
It increases
What are 5 forms of energy?
- Heat
- Light
- X-rays
- Microwaves
- Mechanical motion
What happens to attenuation if the coefficient increases?
It increases
What happens to penetration if frequency increases?
It decreases
Attenuation
Weakening of sound
