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Ultrasound Physics > Chapter 3: describing sound waves > Flashcards

Chapter 3: describing sound waves Flashcards

1
Q

Define Parameters

A

describe features of a sound wave.

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2
Q

what the seven paramets are used for?

A

they are values used to characterize a sound wave

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3
Q

list the seven parameters

A

PERIOD
FREQUENCY
INTENSITY
POWER
AMPLITUDE
WAVELENGTH
PROPAGATION SPEED

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4
Q

PETER
FELL
IN
PRACTICE
AFTER
WAVING
(AT) SALLY

A

PERIOD
FREQUENCY
INTENSITY
POWER
AMPLITUDE
WAVELENGTH
SPEED

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5
Q

source

A

the transducer and the ultrasound system

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6
Q

medium

A

soft tissue

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7
Q

period

Define

A

the time it takes a wave to vibrate a single cycle.

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8
Q

the time from the start of one cycle to the start of the next.

A

period

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9
Q

Units for period

A

time (seconds,microseconds

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10
Q

what is period determined by?

A

the sound source only

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11
Q

is period adjustable?

A

no

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12
Q

What are the seven acoustic parameters?

A

Frequency
period,
wavelength,
propagation of speed,
intensity,
amplitude
and power.

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13
Q

Frequency

A

the number of events that occur in a specific duration of time

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14
Q

in diagnostic ultrasound, the frequency of a wave is described as

A

the number of cycles that occur in one second

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15
Q

Unit for frequency

A

per seconds, 1/second, hertz, Hz

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16
Q

Hertz is another way to say

A

per second

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17
Q

Is frequency adjustable?

A

no

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18
Q

what is frequency determined by?

A

the sound source only

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19
Q

frequency for infrasound

A

less than 20 Hz

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20
Q

frequency for ultrasound

A

greater than 20 kHz or 20,000 Hz

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21
Q

frequency for audible

A

Between 20Hz and 20 kHz

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22
Q

frequency for diagnostic ultrasound

A

1MHz to 20MHz

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23
Q

Why is frequency important?

A

It affects the penetration and image quality

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24
Q

What is the relationship between period and frequency?

A

Period and frequency are inversely related to each other

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25
Q

As frequency increases, period____

A

decreases

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26
Q

As frequency decreases, period____

A

increases

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27
Q

Period and Frequency have a special relationship called….

A

Reciprocal

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28
Q

Formula for period and frequency

A

period x frequency =1

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29
Q

A wave takes up 1/8 of a second to vibrate up and down. What is the period and the frequency?

A

Period = 1/8
Frequency = 8
1/8x8=1`

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30
Q

The higher the frequency

A

the lower the period

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31
Q

which of the following waves is infrasonic?
4 Mhz
400 kHz
28 Hz
2 Hz

A

2 Hz
less than 20Hz cannot be heard

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32
Q

which wave is ultrasonic?
400 mHz
4 MHz
28 Hz
2 Hz

A

4 MHz
greater than 20kHz cannot be heard

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33
Q

indetify all which are audiable
4 MHz
400 kHz
28 Hz
2 Hz

A

4 MHz, 400kHz,2 Hz are all audiable

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34
Q

which of the following has the longest period
2MHz
4,000 Hz
6 Hz
1 kHz

A

6Hz

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35
Q

which has the highest frequency
8 s
80 µseconds
8 Ms
8000 ks

A

8 µseconds

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36
Q

The three bigness parameters

A

IPA
intensity
power
amplitude

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37
Q

Three parameters used to describe the size, magnitude, or strength of a sound wave

A

the three bigness parameters, Intensity, power, amplitude

38
Q

define amplitude

A

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

39
Q

which parameter defines the “bigness” of a wave

A

amplitude

40
Q

Units for amplitude

A

decibels (dB) any units associated with acoustic variables
-pressure; pascals (pa)
-density; grams/cubic cm
-particle motion; units of distance

41
Q

what is amplitude determined by?

A

sound source

42
Q

is amplitude adjustable?

A

Yes!

43
Q

what is the difference between amplitude and peak-to-peak amplitude

A

amplitude is measured by the MIDDLE or UNDISTURBED, value to the maximum value

44
Q

Peak-to-peak amplitude

A

the difference between maximum and minimum values of an acoustic variable,
(twice the value of amplitude)

45
Q

Power

A

the rate of energy transferor rate at which work is performed

46
Q

power is like what other parameter? in what sense?

A

power is like amplitude. they both describe the “bigness” of a wave

47
Q

units for power

A

Watts or (W)

48
Q

is power adjustable?

A

Yes!

49
Q

what is power determined by?

A

They are determined by the sound source`

50
Q

how are power and amplitude related?

A

both amplitude and power describe the size or magnitude of a wave.

51
Q

when power increases….. amplitude

A

increases

52
Q

Power is proportional to the waves amplitude squared

A

power ∝ amplitude^2

53
Q

what relationship does power and amplitude have

A

the are directly proportional

54
Q

what happens to power if amp^2 is increased by a factor of 3

A

power is increased by a power of 9

55
Q

what happens to power if amp^2 is decreased by a factor of 2

A

power is decreased by a power of 4

56
Q

Intensity

A

The concentration of energy in a sound beam

57
Q

units for Intensity

A

W/cm^2

58
Q

what is intensity determined by?

A

Source

59
Q

Is intensity adjustable?

A

Yes!

60
Q

intensity relates

A

to how the power in a wave is spread or is distributed in a space, therefore making it dependent on power and area

61
Q

Intensity is proportional to

A

power

62
Q

Intensity (W/cm^2)=

A

power (w)/ area (cm^2)

63
Q

intensity is proportional to

A

amplitude ^2

64
Q

what happens to intensity if a waves power is doubled?

A

Intensity is also doubled

65
Q

what three parameters tend to be directly related

A

intensity, power, and amplitude

66
Q

what happens to intensity when a waves amplitude^2 is doubled

A

the intensity increases four times its original value.

67
Q

Wavelength

A

The distance or length of one complete cycle

68
Q

unit for wavelength

A

length (mm,meters,inches,feet…)

69
Q

what is wavelength determined by?

A

source and the medium

70
Q

true or false? is wavelength the only parameter determined by both source and the medium

A

true

71
Q

is wavelength adjustable?

A

no

72
Q

λ = c/f

A

wavelength (mm) = propagation speed (µs)/frequency (MHz

73
Q

What is the difference between period and wavelength

A

-period refers to the TIME it takes to complete a single cycle
-wavelength refers to the LENGTH or DISTANCE of a single cycle

74
Q

What is the relationship between wavelength and frequency?

A

wavelength and frequency are INVERSELY related. As f increases w decreases.

75
Q

the lower the frequency … (wl)

A

the longer the wavelength

76
Q

If a waves frequency is twice that of another

A

wavelength will be half as much

77
Q

what is the wavelength of 1MHz in soft tissue?

A

1.54 mm

78
Q

to find the wavelength in soft tissue

A

divide 1.54 mm by the frequency in MHz

79
Q

why is wavelength important in diagnostic imaging?

A

shorter wavelengths are created by high frequency; resulting in higher quality images with greater detail

80
Q

Propagation Speed

A

the rate at which sound travels through a medium

81
Q

what is the unit for speed?

A

m/s or mm/s

82
Q

what is speed determined by?

A

the medium ONLY

83
Q

is speed adjustable?

A

no

84
Q

what is the speed of sound in soft tissue?

A

1,540 m/s or1.54 mm/s or 1.54 km/s

85
Q

list the speed of sound in biologic tissue

A

-lung
-fat
SOFT TISSUE
-liver
-blood
-muscle
-tendon
-bone

86
Q

order of sound traveling
fastest to slowest

A

solids>liquids>gases

87
Q

formula for speed

A

speed (m/s)= frequency (Hz) X wavelength (m)

88
Q

two characteristics that affect speed

A

-stiffness (bulk modulus) :how squishy something is
-density; object weight/mass

89
Q

what relationship do stiffness and speed have

A

direct relationship

90
Q

the opposite of stiffness

A

elasticity and compressability

91
Q

what relationship do density and speed have?

A

they are inversely related

Ultrasound Physics (10 decks)

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