Term
| List four Acoustic variables |
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Definition
| pressure, density, temperature, paricle displacement. |
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Term
| Amplitude is __________ of frequency. |
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Definition
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Term
| What is it called when two waves have both maximum and minimum amplitudes the same? |
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Definition
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Term
| When are two waves out of phase? |
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Definition
| when the maximum and minimum amplitudes occur at different times |
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Term
| What is the difference between constructive and destructive interference? |
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Definition
| Constructive results in a new wave with a larger amplitude. Destructive interference results in a new wave with a smaller amplitude. |
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Term
| Define power, include the mathmatical equation. |
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Definition
Power is the amount of work performed by the wave per unit of time.
P=W/t |
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Term
| What is the unit of power? |
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Definition
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Term
True or False.
Power cannot be adjusted by the technologist. |
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Definition
False!
Power CAN be adjusted by the technologist. |
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Term
Power is a rate at which:
a. amplitude is increased
b. time is decreased
c. energy is transferred to the media by the sound beam
d. the amplitude of the beam decreases as the sound propagates |
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Definition
| c. rate at which energy is transferred to the media by the sound beam. |
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Term
| Why is it recommended to the the power setting low on the US system? |
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Definition
| To avoid large transfer of energy into the tissue (heating). |
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Term
| power of the US beam ______ as the sound _______ through the tissue, because energy is lost. |
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Definition
Decreases; Propagates.
Power of the US beam decreases as the sound propagates through the tissue, because energy is lost. |
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Term
True or False.
Intensity is related to the pitch of the sound. |
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Definition
False!
Intensity is related to the loudness of the sound. |
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Term
| Write the equation for Intensity and the units used. |
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Definition
I=P (power)/ Ar (area)
Units is Watt/cm2 |
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Term
Name the maximum intensities for:
Unfocused transducer
Focused transducer |
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Definition
Unfocused transducer- 100mW/cm2
Focused transducer- 1W/cm2 |
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Term
| What is Power proportional to? |
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Definition
Intensity and Amplitude^2
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Term
| If power is increased by the factor of nine, how does the amplitude of the wave change? |
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Definition
| Amplitude increases by a factor of 3 |
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Term
| If amplitude is halved, how is the power changed? |
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Definition
| Power decreased by a factor of 4, |
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Term
| What is Intensity proportional to? |
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Definition
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Term
| If power is doubled, what happens to intensity? amplitude? |
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Definition
| I increases by a factor of 2, A increases by a factor of squareroot of 2. |
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Term
| Log 100 is the same as what? |
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Definition
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Term
Complete the operations of log functions:
- Log a+log b=
- Log a - log b=
- Log (ab)=
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Definition
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Term
| Explain the scale of Decibel. What does it represent? |
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Definition
| Decibel is a relative logrithmic scale. It represents a ratio of final or initial values. |
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Term
| Write the formula describing decibels. |
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Definition
| dB= 10 Log (Final Value/Initial Value) |
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Term
| A sonographer increases the output power by 3 dB. How did the power change in linear scale? |
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Definition
dB= 10 Log Final/Initial
3dB= 10 log final/initial
.3=log Pfinal/Pinitial
10^(.3)=2
Answer is 2 |
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Term
Technologist increases the intesnity of the ultrasound by 6 dB. What is the increase in linear scale? What is the final intensity?
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Definition
6 dB=10 log Pf/Pi
10^(6)=Pf/Pi
4
There is an increase by a factor of 4.
The final intensity is undeterminable due to lack of information. |
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