Describing Sound Waves

Question 1

Name the seven acoustic parameters

Answer 1

Frequency/Period, Amplitude/Power/Intensity, Wavelength/Propagation Speed

Question 2

Define period

Answer 2

Time necessary to complete a single cycle

Question 3

What are the units of period?

Answer 3

any time units

Question 4

What are the typical values of period?

Answer 4

0.06 - 0.5 microseconds
0.00000006 - 0.0000005 seconds
6x10^-8 - 5x10^-7 seconds

Question 5

Period is determined by?

Answer 5

the sound source

Question 6

Is period adjustable by the sonographer?

Answer 6

No

Question 7

Define Frequency

Answer 7

The number of cycles that occur in one second

Question 8

What are the units of frequency?

Answer 8

Hz (1 cycle per second)

Question 9

What are the typical values of frequency?

Answer 9

2-15 MHz
2 million - 15 million cycles per second

Question 10

What is the frequency determined by?

Answer 10

the sound source

Question 11

Is the frequency adjustable by the sonographer?

Answer 11

No (assuming everything remains constant)

Question 12

Infrasound is less than _______ Hz

Answer 12

20

Question 13

Range of frequencies for audible sound

Answer 13

20 Hz - 20,000 Hz (20 MHz)

Question 14

Ultrasound has frequencies higher than ______.

Answer 14

20,000 Hz (20 MHz)

Question 15

Frequency and period have an ________ and _______ relationship.

Answer 15

Inverse; reciprocal

Question 16

Period x frequency = ?

Answer 16

1

Question 17

What are the bigness parameters?

Answer 17

Amplitude, Power, Intensity

Question 18

What do the bigness parameters describe?

Answer 18

The size, magnitude, or strength of sound waves

Question 19

What is amplitude?

Answer 19

The difference between the maximum/minimum value and the average of an acoustic variable

Question 20

What are the units for amplitude?

Answer 20

any of the acoustic variable units (Pa, g/cm^3, cm)

Question 21

What are the typical values of amplitude?

Answer 21

1 million pascals - 3 million pascals
1MPa - 3 MPa

Question 22

What is amplitude determined by?

Answer 22

the sound source

Question 23

What is amplitude determined by?

Answer 23

the sound source and eventually the medium

Question 24

Can amplitude be adjusted by the sonographer?

Answer 24

Yes

Question 25

Define power

Answer 25

the rate of energy transfer

Question 26

What are the units of power?

Answer 26

watts

Question 27

What are the typical values of power?

Answer 27

0.004 - 0.090 watts 4 - 90 milliwatts

Question 28

What is power determined by?

Answer 28

sound source

Question 29

Is power adjustable by the sonographer?

Answer 29

Yes

Question 30

Amplitude and power have a _______ relationship

Answer 30

direct

Question 31

Power is proportional to amplitude ______.

Answer 31

squared

Question 32

If amplitude was increased by a factor of 3, the power would be increased by a factor of?

Answer 32

9 (3 x 3)

Question 33

If the amplitude is decreased by a factor of 1/2, the power is decreased by a factor of?

Answer 33

1/4 (1/2 x 1/2)

Question 34

Define intensity

Answer 34

The concentration of energy in a sound beam

Question 35

What are the units of intensity?

Answer 35

watts/cm^2

Question 36

What are the units of intensity?

Answer 36

watts/cm^2

Question 37

What are the typical values of intensity?

Answer 37

0.01 - 300 W/cm^2

Question 38

What are the typical values of intensity?

Answer 38

0.01 - 300 W/cm^2

Question 39

What is intensity determined by?

Answer 39

The sound source

Question 40

Is intensity adjustable by the sonographer?

Answer 40

Yes (b-mode or TGCs)

Question 41

Intensity is ______ to power

Answer 41

Proportional

Question 42

When a waves power doubles, intensity will _____.

Answer 42

double

Question 43

Intensity is proportional to amplitude ______.

Answer 43

squared

Question 44

When a wave’s amplitude is increased by a factor of 2, the intensity is increased by ______.

Answer 44

4

Question 45

Define wavelength

Answer 45

the distance or length of one complete cycle

Question 46

What are the units of wavelength?

Answer 46

mm, cm, m

Question 47

What are the typical values of wavelength?

Answer 47

0.1 - 0.8 mm (in soft tissue)

Question 48

What is the wavelength determined by?

Answer 48

the source and medium

Question 49

Which is the only parameter determined by both the source and medium?

Answer 49

wavelength

Question 50

Is the wavelength adjustable by the sonographer?

Answer 50

no

Question 51

Wavelength and frequency have an _______ relationship.

Answer 51

inverse

Question 52

In soft tissue, sound with a frequency of 1 MHz has a wavelength of ________.

Answer 52

1.54 mm

Question 53

Propagation speed in soft tissue is?

Answer 53

1,540 m/s, 1.54 km/s, 1.54 mm/microsec

Question 54

True or False: A sound wave with a short wavelength and a high frequency produce high quality images

Answer 54

True

Question 55

Define Propagation speed

Answer 55

The rate at which a sound wave travels through a medium

Question 56

What are the units of propagation speed?

Answer 56

m/s, mm/ms

Question 57

What are the typical values of propagation speed?

Answer 57

1.54 mm/microsec range: 500 m/s - 4000 m/s

Question 58

Propagation speed is determined by?

Answer 58

the medium only

Question 59

Is propagation speed adjustable by the sonographer?

Answer 59

No

Question 60

When does propagation speed change?

Answer 60

Only when going from one medium to the next

Question 61

What is the speed of sound in air?

Answer 61

330 m/s

Question 62

What is the speed of sound in metals?

Answer 62

2,000 - 7,000 m/s

Question 63

What two characteristics of the medium affect speed?

Answer 63

stiffness, density

Question 64

Define stiffness?

Answer 64

The ability of an object to resist compression

Question 65

Stiffness is also called?

Answer 65

bulk modulus

Question 66

Stiffness and speed have a _______ relationship

Answer 66

direct

Question 67

What is the opposite of stiff?

Answer 67

Elasticity or compressibility

Question 68

What is density?

Answer 68

the relative weight of a material

Question 69

Density and speed are ______ related.

Answer 69

inversely

Question 70

What is the formula for frequency?

Answer 70

prop. speed / wavelength

Question 71

What is the formula for wavelength?

Answer 71

prop. speed / frequency

Question 72

What is the formula for prop. speed?

Answer 72

wavelength x frequency