1 Ch 3: Describing Sound Waves

Question 1

The source of the sound wave is the…

Answer 1

ultrasound system and transducer.

Question 2

The medium is the…

Answer 2

tissues through which the sound is traveling.

Question 3

Period is the…

Answer 3

time it takes a wave to vibrate a single cycle; the timefrom the start of one cycle to the start of the next cycle.

Question 4

Period is reported in units of…

Answer 4

time, such as microseconds, seconds, hours, or days.

Question 5

The typical value of period in diagnostic u/s is…

Answer 5

.06 to .5 microseconds.

Question 6

Period is determined by…

Answer 6

the sound source only, not by the medium.

Question 7

Is period adjustable by the sonographer?

Answer 7

No.

Question 8

Frequency is…

Answer 8

the number of particular events that occur in a specific duration of time. In u/s, the # of cycles per second.

Question 9

Frequency is reported in units of…

Answer 9

per second, 1/second, hertz, or Hz.

Question 10

In clinical imaging, the typical frequency range is…

Answer 10

from approximately 2 MHz to 15 MHz.

Question 11

Frequency is determined by…

Answer 11

the sound source only.

Question 12

Is frequency adjustable by the sonographer?

Answer 12

No.

Question 13

Sound is described as infrasonic if its frequency is…

Answer 13

less than 20 Hz.

Question 14

Sound is described as audible if its frequency is…

Answer 14

between 20 Hz and 20,000 Hz.

Question 15

Sound is described as ultrasonic if its frequency is…

Answer 15

higher than 20,000 Hz (20 kHz).

Question 16

How are period and frequency related to each other?

Answer 16

Inversely. As one increases, the other decreases.

Question 17

Period and frequency have a special inverse relationship called…

Answer 17

reciprocal. If multiplied together, the result is one.

Question 18

Amplitude is…

Answer 18

the ‘bigness’ of a wave; the difference between the maximum (or minimum) value and the baseline value.

Question 19

Amplitude is reported in units of…

Answer 19

pressure (pascals or Pa), density (g/cm^3), particle motion (any distance), or decibels (dB).

Question 20

In clinical imaging, typical amplitude ranges from…

Answer 20

1 million pascals to 3 million pascals.

Question 21

Amplitude is determined by the…

Answer 21

sound source (though it does decrease as the wave travels through the body).

Question 22

Is amplitude adjustable by the sonographer?

Answer 22

Yes.

Question 23

Peak-to-peak amplitude is…

Answer 23

the difference between the maximum and minimum values (not just between one extreme and the baseline).

Question 24

Power is the…

Answer 24

rate of energy transfer; the rate at which work is performed.

Question 25

Power is reported in units of...

Answer 25

watts (W).

Question 26

In clinical imaging, typical power ranges from...

Answer 26

.004 to .09 watts.

Question 27

Power is determined by the...

Answer 27

sound source (though the power decreases as the wave travels through the body).

Question 28

Is power adjustable by the sonographer?

Answer 28

Yes.

Question 29

The bigger the wave, the more energy is transferred. So as the amplitude changes, power changes proportionally. What is the proportion?

Answer 29

Power is proportional to amplitude SQUARED.

Question 30

Intensity is...

Answer 30

the concentration of energy in a sound beam.

Question 31

Intensity is reported in units of...

Answer 31

watts/square centimeter (W/cm^2).

Question 32

In clinical imaging, typical intensity ranges from...

Answer 32

.01 to 300 W/cm^2.

Question 33

Intensity is determined by...

Answer 33

the sound source (though the wave gets less intense as it travels through the body).

Question 34

Is intensity adjustable by the sonographer?

Answer 34

Yes.

Question 35

The 'bigness' parameters are all directly related. What is the proportion of intensity to power?

Answer 35

One to one. If a wave's power is doubled, the intensity is doubled. If a wave's power is quartered, the intensity is quartered.

Question 36

What is the proportion of intensity to amplitude?

Answer 36

Intensity is proportional to amplitude SQUARED.

Question 37

Wavelength is...

Answer 37

the length of one complete cycle.

Question 38

Wavelengh is reported in units of...

Answer 38

mm, meters, or any length.

Question 39

In clinical imaging, wavelength in soft tissue ranges from...

Answer 39

.1 to .8 mm.

Question 40

Wavelength is determined by...

Answer 40

both the sound source and the medium.

Question 41

Is wavelength adjustable by the sonographer?

Answer 41

No.

Question 42

What is the relationship between wavelength and frequency?

Answer 42

They are inversely related. As one increases, the other decreases.

Question 43

What is the wavelength of 1 MHz sound in soft tissue?

Answer 43

1.54 mm

Question 44

How do you find the wavelength of a sound wave in soft tissue?

Answer 44

wavelength (mm) = 1.54 mm per microseconds divided by frequency (MHz)

Question 45

Why is wavelength important in u/s?

Answer 45

Shorter wavelengths are created by higher frequency sound. The higher the frequency, the clearer the image.

Question 46

Propagation speed is...

Answer 46

the rate at which a sound wave travels through a medium.

Question 47

Speed is reported in units of...

Answer 47

distance divided by time (m/s, mm/microseconds, or miles per hour).

Question 48

In the body, the speed of sound ranges from...

Answer 48

500 m/s to 4,000 m/s depending on the tissue.

Question 49

Speed is determined by...

Answer 49

the medium.

Question 50

Is speed adjustable by the sonographer?

Answer 50

No.

Question 51

What is the speed of sound in soft tissue?

Answer 51

1,540 m/s

Question 52

What is the speed of sound in lung tissue?

Answer 52

500 m/s

Question 53

What is the speed of sound in bone?

Answer 53

3,500 m/s

Question 54

What two characteristics determine the speed of sound in a given medium?

Answer 54

Stiffness and density

Question 55

Stiffness describes...

Answer 55

the ability of an object to resist compression.

Question 56

How are stiffness and speed related to each other?

Answer 56

Directly. The stiffer the material, the faster the sound's speed.

Question 57

What other terms describe stiffness?

Answer 57

Bulk modulus (same as stiff), elasticity and compressability (opposite of stiff)

Question 58

Density describes...

Answer 58

the relative weight of a material.

Question 59

How are density and speed related to each other?

Answer 59

Inversely. The denser the material, the slower the sound's speed.

Question 60

Is stiffness or density more important to speed?

Answer 60

Stiffness has the greater influence.