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Physics I > Properties of Sound Waves (Continuous Wave and Pulsed Wave Parameters) > Flashcards

Properties of Sound Waves (Continuous Wave and Pulsed Wave Parameters) Flashcards

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1
Q

Properties of Sound Waves

Sound

  • -General
  • -_____and _____
  • -_____and _____Sound Waves
  • -Wave Descriptors

Sound-Propagation Media

Acoustic Velocity Equation

Sound Transmission

A

compression
rarefation
longitudinal
transverse

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2
Q

Sound

General
A _____ is a propagating disturbance that moves energy from one location to another

A

wave

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3
Q

Energy

Mechanical:
____ waves
_____waves
_____waves

Electromagnetic:
_____waves
_____
_____waves

A 
ocean
seismic
sound
radio
x-rays
light
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4
Q

Sound

General
Sound is a particular type of wave

Quantities of these variations are called acoustic variables

______
_____
_____Motion
_____

A

Density
pressure
particle
temperature

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5
Q

Sound

Valuable Advice – Acoustic Variables

Don’t – ______
Pinch – _____
Panthers Middle - _____Motion
Toe -_____

A

Density
pressure
particle
temperature

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6
Q

Sound

Compression and Rarefaction

Compression
Region of _____ pressure and density in a longitudinal wave
Corresponds to a _____wave peak

Rarefaction
Region of _____pressure and density in a _____wave
Corresponds to a sine wave trough

A

high
sine
low
longitudinal

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7
Q

Sound

Compression and Rarefaction

Particles _____ back and forth as sound waves travel through the medium

A

oscillate

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8
Q

Sound

above 20,000 Hz = ______

20 MHz and Beyond

≈ 15 - 20 MHz
_____Medical Ultrasound
1-2 MHz

               above 20,000 Hz \_\_\_\_\_=      20,000 Hz  Sound              20 Hz

_____= below 20 Hz
(ocean and seismic waves)

A

ultrasound
Diagnostic
audible
infrasound

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9
Q

Sound

Compression and Rarefaction

–Sound waves require a _____

–They cannot travel through a _____

A

medium

vacuum

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10
Q

Sound

Longitudinal and Transverse Sound Waves

= _____ is a mechanical longitudinal (compressional) wave

P waves are _____waves

S waves are _____waves

Particle motion _____(same direction)

Particle motion _____(different direction)

A 
sound
longitudinal
transverse
parallel
perpendicular
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11
Q

Sound

Wave Descriptors

–______

–_____

–_____

–_____

–Acoustic _____, a.k.a., propagation speed

–_____

A 
amplitude
frequency
period
wavelength
velocity
intensity
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12
Q

Sound

Wave Descriptors – AMPLITUDE

Relates to the ______ of the sound wave

Equals the

  • -maximum variation of an acoustic _____
  • -maximum value minus the _____value
  • -difference between _____value and _____value

NOT the difference between _____and _____values

A 
strength
variable
normal
average
minimum
maximum
minimum
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13
Q

Sound

Wave Descriptors – AMPLITUDE

Units are any unit of an acoustic variable

  • -______ = degrees
  • -_____= Pascal’s (Pa, MPa)
A

temperature

pressure

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14
Q

Sound

Wave Descriptors – FREQUENCY

  • Number of ____ that occur in one second
  • Determined by the _____source
  • Affects _____and _____RESOLUTION
A

cycles
sound
penetration
axial

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15
Q

Sound

Wave Descriptors – FREQUENCY

____/____ = 1 Hertz

Humans are capable of hearing frequencies between _____- _____Hz = AUDIBLE SOUND

Frequencies > _____Hz = ULTRASOUND

Frequencies < _____Hz = INFRASOUND

A 
cycle
second
20
20,000
20,000
20
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16
Q

Sound

Wave Descriptors – FREQUENCY

Typical in Diagnostic Medical Ultrasound

__-__ MHz through __-__ MHz

Great penetration
Lousy _____resolution

Great axial resolution
Lousy _____

A 
1
2
10
20
axial
penetration
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17
Q

Sound

Wave Descriptors – FREQUENCY

Frequency (Hz) = 1/___ (sec)

_____and Frequency are RECIPRCALS

A

period

period

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18
Q

Sound

Wave Descriptors – FREQUENCY

Frequency INCREASES——–Period ________
Period INCREASES——–Frequency _____

Period and Frequency are _____PROPORTIONAL

A

decreases
decrease
inversely

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19
Q

Sound

Wave Descriptors – FREQUENCY HARMONICS

–In conventional imaging, the transducer transmits and receives sound waves of a given frequency; received signal is _____ in intensity as it is attenuated by the tissue

A

lower

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20
Q

Sound

Wave Descriptors – FREQUENCY HARMONICS

–Dependence of propagation speed on pressure causes strong pressure (sound) waves to change _____ as they propagate

–The higher pressure portions of the wave travel faster than the _____ pressure portions

A

shape

lower

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21
Q

Sound

Wave Descriptors – FREQUENCY HARMONICS

The original sinusoidal wave progresses towards a non-_____ shape

Propagation in which speed depends on pressure and the wave shape changes is called non-_____ propagation

A

sinusoidal

linear

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22
Q

Sound

Wave Descriptors – FREQUENCY HARMONICS

Harmonic signals are not generated from the US system itself; they are generated in the body as a result of interactions with _____ or contrast agents distorting the signal

In harmonic imaging, the returning signal is actually a combination of _____

A

tissue

frequencies

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23
Q

Sound

Wave Descriptors – FREQUENCY HARMONICS

Harmonics are ____ and odd multiples of the fundamental frequency

A

even

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24
Q

Sound

Wave Descriptors – FREQUENCY HARMONICS

In harmonic imaging, the returning signal is actually a combination of _______

It contains not only the fundamental signal that was originally transmitted, but also the harmonic signal, which is twice the _____

A

frequencies

frequency

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25
Q

Sound

Wave Descriptors – FREQUENCY HARMONICS

Advantages of harmonic imaging include:

significant improvements in _____ (lateral) and contrast resolution

(due to the improvement in beam _____ and a reduction in side lobes)

A

spatial

width

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26
Q

Sound

Wave Descriptors - PERIOD

Length of _____ to complete ONE CYCLE

_____ from start of one cycle to start of the next cycle

Determined by the _____ SOURCE

A

time
time
sound

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27
Q

Sound

Wave Descriptors – PERIOD

Unit = _____, μs (microsecond)

Common US periods < 1μs

Period (ms) = 1/_____(MHz)

Period and Frequency are _____

A

second
frequency
reciprocals

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28
Q

Sound

Wave Descriptors - PERIOD

Period DECREASES——–Frequency _____

Period INCREASES——–Frequency _____

Period and Frequency are _____ PROPORTIONAL

A

increases
decrease
inversely

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29
Q

Sound

Wave Descriptors – Wavelength

_____ of space over which one cycle occurs

Determined by _____ source AND _____

A

length
sound
medium

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30
Q

Sound

Wave Descriptors – Wavelength

λ

Unit = _____, mm (any distance measurement)

1 mm = _____m

Common US wavelengths in soft tissue are:
_____- _____mm

A

meters

  1. 001
  2. 1
  3. 8
31
Q

Sound

Wave Descriptors – Wavelength

Wavelength (mm) = _____ Speed (mm/μs)/Frequency (MHz)

λ = c/f

For Soft Tissue:

Wavelength = _____(mm/μs)/_____(MHz)

A

propagation
1.54
frequency

32
Q

Sound

Wave Descriptors – Wavelength

If: λ = c/f

Then as:

Wavelength increases - Frequency ______

Wavelength decreases - Frequency _____

Wavelength and Frequency are
_____PROPORTIONAL

A

decreases
increases
inversely

33
Q

Sound

Wave Descriptors - Acoustic velocity,
a.k.a., propagation speed

_____ is the rate at which sound travels through a medium

-vs.-

_____is the rate and direction at which sound travels through a medium

A

speed

velocity

34
Q

Sound

Wave Descriptors - Acoustic velocity

The speed at which sound can travel through a medium

Units: ____/____, mm/μs

Determined ONLY by the _____
In the frequency range of ___– ___ MHz

A 
speed
meters
second
medium
2
20
35
Q

Sound

Wave Descriptors - Acoustic velocity,

ALL sound, regardless of frequency, travels at the SAME ____ through any specific medium

Speed of Sound in Soft Tissue

_____ km/s _____m/s _____mm/μs _____mph

A 
speed
1.54
1,540
1.54
3,500
36
Q

Sound

Wave Descriptors - Acoustic velocity

Different “soft tissues”:

Muscle > Kidney > Liver > Brain > Fat
1,6-1,580 m/s 1,560 m/s 1,550 m/s 1,560 m/s 1,460 m/s

Notice the Big Difference between bone/ST and ST/lung
It’s IMPORTANT!!!!

Bone > Blood > ST > Fat > Lung > Air
4,080 m/s 1,575 m/s 1,540 m/s 1,460 m/s 600 m/s 330 m/s

A

chart

37
Q

Sound

Wave Descriptors – Intensity

The concentration of ____ in a sound beam

The power of the beam divided by the beam’s cross-sectional area

Relates to the _____ of the sound beam

Power (Watts) per unit area (m2)

Unit = W/m2, mW/cm2

A

energy

strength

38
Q

Sound - Propagation Media

What is it about the medium that determines propagation speed?

The medium’s

  • -_____
  • -Bulk Modulus
  • -_____
  • -_____
  • -_____
A

stiffness
density
compressability
elasticity

39
Q

Sound - Propagation Media

Stiffness
–The resistance of a material to _____

Bulk Modulus
–Akin to density; the negative ratio of stress and strain; velocity depends on _____ and bulk modulus of a medium c = √ of bulk modulus/density

Density
–The concentration of _____

A

compression
density
matter

40
Q

Sound - Propagation Media

_____ =
–The ability of an object to return to its original space and volume after a force is no longer acting on it; opposite of stiffness

_____
–The fractional decrease in volume when pressure is applied opposite of stiffness

A

elasticity

compressibility

41
Q

Sound - Propagation Media

Rule of Thumb:

Stiffness INCREASES-Speed _______

Density INCREASES-Speed _____

Elasticity INCREASES-Speed _____

Compressability INCREASES-Speed _____

Doesn’t play by rules:
Bulk Modulus INCREASES-Speed _____

A 
increases
decreases
decreases
decreases
increases
42
Q

Acoustic Velocity Equation

Propagation Speed (m/s) =

_____ (Hz) x _____ (meters)

c = fλ

c m/s= f Hz x λ m -or- c mm/μs = f MHz x λ mm

if, c = fλ , then

f = c/λ and λ = c/f

A

frequency

wavelength

43
Q

Sound Transmission

In sonography, the sound source as well as the detector of echoes is the transducer

______ may operate in a continuous or pulsed ultrasound-generating mode, depending of the application

_____-wave (CW) transmission continuously emits a constant frequency and constant peak-pressure amplitude sound wave from the source

_____-wave (PW) transmission is a short- duration burst of sound (a few cycles in length) emitted from the sound source

A

transducer
continuous
pulsed

44
Q

Pulsed Waves

For imaging, a _____ sends out a short burst of ultrasound, followed by a period of silence to “listen” for returning echoes before another burst is generated

A _____cannot “talk” and “listen” at the same time

Pulsing methods include:

  • -Rapidly switched gating turning on for a short period of time
  • -_____ capacitor
A

transducer
transducer
charged

45
Q

Pulsed Waves

Frequency, period, wavelength and propagation speed are still appropriate parameters, however there are additional parameters to consider:

Pulse Repetition ______

Pulse Repetition ______

_____ Pulse Length

_____Duration

_____ Factor

A 
frequency
period
spatial
pulse
duty
46
Q

Pulse Repetition Frequency
a.k.a.: PRF, Pulse Repetition Rate

Number of _____ that occur in one second

1 pulse/second

Units : _____

A

pulses

hertz

47
Q

Pulse Repetition Frequency
a.k.a.: PRF, Pulse Repetition Rate

Typical to clinical imaging: ___ - ___ Hz (4-15 KHz)

Determined by the _____

Can be changed by sonographer

Although not directly changed………..because _____ varies with depth, the sonographer changes PRF indirectly when depth or FOV is altered

A

4,000
15,000
source
PRF

48
Q

Pulse Repetition Frequency
a.k.a.: PRF, Pulse Repetition Rate

DEPTH

PRF depends on imaging _____

depth increases ⇒ PRF _____

depth is _____ proportional to PRF

A

depth
decreases
inversely

49
Q

Pulse Repetition Frequency
a.k.a.: PRF, Pulse Repetition Rate

PRF = 1/___

PRF increases ⇒ PRP _____

PRF is _____ proportional to PRP

depth increases ⇒ PRP _____

A

PRP
decreases
inversely
increases

50
Q

Pulse Repetition Period
a.k.a.: PRP

____ from the start of one pulse to the start of the next pulse

Time pulse is “on” + time pulse is “off”

Transmitting and receiving time

A

time

51
Q

Pulse Repetition Period
a.k.a.: PRP

Units : seconds, micro-, milli-

Typical to clinical imaging: ___ – ___ ms

Determined by the _____

Can be changed by sonographer

A

0.07
0.25
source

52
Q

Pulse Repetition Period
a.k.a.: PRP

DEPTH

PRP depends on imaging depth

depth increases ⇒ PRP _____

depth is _____ Proportional to PRP

A

increases

directly

53
Q

Pulse Repetition Period
a.k.a.: PRP

PRP = 1/PRF

PRF increases ⇒ PRP _____

PRF is _____ proportional

A

decreases

inversely

54
Q

Pulse Duration
a.k.a.: PD, Temporal Pulse Length

____ from the start of a pulse to the end of the same pulse

Time interval for one complete pulse

Only the “on” or transmitting time

A

time

55
Q

Pulse Duration
a.k.a.: PD, Temporal Pulse Length

Unit: ms, μs

Typical to clinical imaging: ___ – ___ μs

Determined by the _____

Characteristic of the machine and transducer; indicates the effectiveness of the backing material

A

0.1
1.5
source

56
Q

Pulse Duration
a.k.a.: PD, Temporal Pulse Length

Closely associated with Spatial Pulse Length

Determines _____ resolution

DOES NOT change with imaging _____

CANNOT be changed by the _____

A

axial
depth
sonographer

57
Q

Pulse Duration
a.k.a.: PD, Temporal Pulse Length

PD = # of cycles in the pulse (nc) x period

period increases ⇒ pulse duration ______

of cycles in the pulse (nc) increases ⇒ PD _____

period and # of cycles in the pulse (nc) are
_____ proportional to PD

A

increases
increases
directly

58
Q

Pulse Duration
a.k.a.: PD, Temporal Pulse Length

IF: period = 1/frequency

Then: PD = # of cycles in the pulse/frequency

frequency increases ⇒ pulse duration ______

frequency is
_____ proportional to Pulse Duration

A

decreases

inversely

59
Q

Duty Factor
a.k.a.: DF, Duty Cycle

Fraction of ____ that the sound is “on” or the machine is transmitting sound or producing a pulse

Units: UNITLESS!!!

Max. = 1.0 (100%) Min. = 0.0 (0%)

Typical to clinical imaging: 0.001-0.01 (0.1-1%)

Important in determining some intensity parameters for bioeffects

A

time

60
Q

Duty Factor
a.k.a.: DF, Duty Cycle

Determined by the ______

Can be changed by sonographer, by adjusting the imaging _____

Duty Factor = PD/PRP
- or -
Duty Factor = PD ∙ PRF

A

source

depth

61
Q

Duty Factor
a.k.a.: DF, Duty Cycle

Any action that ⇑ the % of time US is transmitting ⇑ Duty Factor

as, PRF⇑, Duty Factor ____

as, PD⇑, Duty Factor _____

Duty Factor is _____ proportional to PRF and PD

A

increases
increases
directly

62
Q

Duty Factor
a.k.a.: DF, Duty Cycle

Any action that ⇓ the % of time US is transmitting ⇓ Duty Factor

as, PRP⇑, Duty Factor ____

as, Depth ⇑, Duty Factor _____

Duty Factor is _____ proportional to PRP and Depth

A

decreases
decreases
indirectly

63
Q

Spatial Pulse Length
aka: SPL

_____ of distance a pulse occupies

_____ from the start of a pulse to the end of the pulse

A

length

distance

64
Q

Spatial Pulse Length
aka: SPL

Unit: mm ,meters

Typical to clinical imaging: ___ –___ mm

Determined by the _____ AND _____

Cannot be changed by the sonographer

Determines _____/longitudinal resolution

A

0.1
2.5
source
medium
axial

65
Q

Spatial Pulse Length
aka: SPL

SPL = # of ____ in the pulse x ____

or –
In ST:
SPL = # of cycles per pulse x 1.54/frequency

Wavelength increase ⇒ SPL _____

cycles in the pulse increase ⇒ SPL _____

A

cycles
wavelength
increase
increase

66
Q

Spatial Pulse Length
aka: SPL

SPL = nc x λ SPL = nc x 1.54/frequency

SPL is ____ proportional to
wavelength and # cycles in pulse

Frequency increase ⇒ SPL _____

SPL is _____ proportional to frequency

A

directly
decrease
indirectly

67
Q

Bandwidth

Range of _____ contained within an US pulse

A parameter that describes the distribution of frequency components in a wave

Fractional bandwidth = bandwidth/operating frequency

Fractional bandwidth is _____

Determined by transducer fabrication and design of electronics

A

frequencies

unitless

68
Q

Bandwidth

short pulse ⇒ ____ (large) bandwidth

long pulse ⇒ narrow (_____) bandwidth

short SPL ⇒ broad (_____) bandwidth

broad (large) bandwidth ⇒ _____Q factor

A

broad
small
large
low

69
Q

Q Factor

Describes the “____” of the frequency of an US wave

Q factor = operating frequency/bandwidth

Q factor is _____

Damping material:
⇑ bandwidth and _____ Q factor

A

purity
unitless
decrease

70
Q

Q Factor

broad bandwidth, ____ Q factor
narrow bandwidth, _____ Q factor

For short pulses, # of pulses ≈ Q-factor
(2-3 cycles per pulse)

Overall system bandwidth determined by transducer and instrument electronics

Wide-bandwidth transducer
(fractional bandwidth of 70%)
you may selectively operate the same transducer at more than one frequency

A

decrease

increase

71
Q

Q Factor

HIGH Q Transducers
Long ring-down time

_____ Pulse

Narrow range of _____

Better Transmitters

Used for Therapy and _____ Doppler

LOW Q Transducers
_____ring-down time

_____ Pulse

_____ range of Frequencies

Better Receivers

Used for _____-Echo Imaging

A 
long
frequencies
CW
short
shorter
wide
pulse
72
Q

Time

Determined by the ____ Source

Period (sec, μs) - _____ to complete one cycle.

Pulse Repetition Period (sec, ms) - _____ from the start of one pulse to the start of to next pulse.

Pulse Duration (sec, μs) - _____ from the start of one pulse to the end of that same pulse.

A

sound
time
time
time

73
Q

Frequency

Determined by the Sound Source

_____ (Hz, MHz) - Number of cycles per second.

Pulse Repetition Frequency, aka: PRF (Hz, kHz) - Number of _____ per second.

A

frequency

pulses

74
Q

Distance

Determined by the _____ Source and the _____

Wavelength (mm) - _____ over which one cycle occurs.

Spatial Pulse Length (mm) - _____ of one pulse; from the start to the end of one pulse.

A

sound
medium
length
length

Physics I (8 decks)

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