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