Sound Wave Principles

Question 1

Compare compressions and rarefactions in terms of pressure and density

Answer 1

Compressions = areas of high pressure and density

Rarefactions = area of low pressure and density

Question 2

What type of wave is a sound wave?

Answer 2

A longitudinal mechanical wave

Question 3

What are the acoustic variables?

Answer 3

1. Temperature
2. Pressure
3. Density
4. Particle motion

Question 4

What is the range in MHz in diagnostic ultrasound?

Answer 4

2-20

Question 5

What type of media have higher sound speeds?

Answer 5

Stiffer material such as bone

Question 6

What are the propagation speeds of gases, liquids, and solids?

Answer 6

Gases < liquids < solids (greatest)

Question 7

Adjust depth changes what factor?

Answer 7

Changes the PRP

Question 8

A shallow image will have a higher or lower PRF?

Answer 8

Higher PRF

Question 9

What happens to the PRP when depth increases?

Answer 9

PRP also increases because it has to travel farther into the body

Question 10

What two factors is PRP controlled by?

Answer 10

Depth and speed of sound

Question 11

What is the term for the time the pulse is ON or the ringing/transmission period?

Answer 11

Pulse duration

Question 12

How do we calculate pulse duration?

Answer 12

number of cycles in a pulse x period

Question 13

How do we calculate duty factor?

Answer 13

PD/PRP

Question 14

What is the formula for SPL?

Answer 14

number of cycles x wavelength

Question 15

What happens to SPL as increases?

Answer 15

SPL decreases because there is less space between each pulse

Question 16

As frequency increases, what happens to spatial resolution?

Answer 16

Improves

Question 17

What is the term for “the range of frequencies contained in a pulse”?

Answer 17

Bandwidth

Question 18

Do shorter pulses have a larger or smaller bandwidth?

Answer 18

Broader bandwidth

Question 19

How to change the amplitude on the ultrasound machine?

Answer 19

Output power button

Question 20

How are power and amplitude related?

Answer 20

Power = Amplitude^2

Question 21

If amplitude is doubled, what happens to the power?

Answer 21

It quadruples

Question 22

How do we calculate intensity?

Answer 22

Power/area

Question 23

What is known as “the rate at which energy passes through a unit area”?

Answer 23

Intensity

Question 24

How do you change intensity in ultrasound?

Answer 24

Changing the focus

Question 25

If amplitude is cut in half, what happens to the intensity?

Answer 25

It decreases by a factor of 4

Question 26

The degree to which a medium will absorb sound is related to what?

Answer 26

Viscosity/density

Question 27

What particular mode of imaging has the largest duty factor?

Answer 27

Continuous wave

Question 28

What advantages can be gained from the ability to steer beams in linear array transducer? (Lecture 5)

A) CD applications

B) Harmonic Imaging

C) Wider fields of view via trapezoidal image formats
D) All of the above

E) A and C