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 (a^{b})=


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. 

