Lesson 5 Flashcards
What is strength of sound measured in? (2)
- Amplitude (A)
2. Intensity (I)
What does amplitude and intensity show?
How loud the sound is
If you have a stronger ultrasound pulse, what will it produce?
A stronger echo
If you have a weaker ultrasound pulse, what will it produce?
A weak echo
What kind of image do you get with a stronger echo?
Better quality
What kind of image do you get with a weaker echo?
Poor quality
Amplitude
Is the maximum variation in pressure
- it is the distance from the baseline to the top/bottom of a wave (height of wave)
What happens to frequency and pitch with longer wavelengths?
Frequency = lower frequency Pitch = lower pitch
What happens with frequency and pitch with shorter wavelengths?
Frequency = higher frequency Pitch = higher pitch
What happens to sound when you have a higher amplitude?
Louder sound
What happens to sound when you have a lower amplitude?
Softer sound
What are 2 units of amplitude?
- Pressure in Pascals (N/m^2)
2. Electrical signal/voltage (V)
What kind of waves transfer energy?
Mechanical
Power
Is the rate at which energy is transferred
What is the units for power?
Watts
- W or mW
Intensity
Is the rate at which energy passes through a unit area
What is the unit for intensity?
mW/cm^2
What is the formula for intensity?
I = P/A
- I = intensity
- P = power
- A = area
What happens to intensity as you decrease power?
Intensity decreases
What happens if you increase power?
Intensity increases
What happens when you decrease area?
Intensity increases
What does intensity depend on?
Area
What effects can increase power have?
Negative side effects
- eg) bioeffects
Focus
Is were area is the smallest
- and intensity is the highest
Where is the image best?
Closest to the focal point
If you double amplitude (2x), what happens to the intensity?
It goes up 4x
If you decrease amplitude 4 times (4x), what happens to the intensity?
It decreases 16 times (16x)
What is intensity closely related to?
Amplitude
- they are directly proportional
What is amplitude and intensity indicators of?
Loudness
What kind of form is sound?
Mechanical
What is the beam area determined by?
The transducer
What is intensity proportional to?
Amplitude^2
- eg) amp is doubled, intensity is 4x
- eg) amp is halved, intensity ia 1/4x
