Properties of Sound Waves (Continuous Wave and Pulsed Wave Parameters) Flashcards
Properties of Sound Waves
Sound
- -General
- -_____and _____
- -_____and _____Sound Waves
- -Wave Descriptors
Sound-Propagation Media
Acoustic Velocity Equation
Sound Transmission
compression
rarefation
longitudinal
transverse
Sound
General
A _____ is a propagating disturbance that moves energy from one location to another
wave
Energy
Mechanical:
____ waves
_____waves
_____waves
Electromagnetic:
_____waves
_____
_____waves
ocean seismic sound radio x-rays light
Sound
General
Sound is a particular type of wave
Quantities of these variations are called acoustic variables
______
_____
_____Motion
_____
Density
pressure
particle
temperature
Sound
Valuable Advice – Acoustic Variables
Don’t – ______
Pinch – _____
Panthers Middle - _____Motion
Toe -_____
Density
pressure
particle
temperature
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
high
sine
low
longitudinal
Sound
Compression and Rarefaction
Particles _____ back and forth as sound waves travel through the medium
oscillate
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)
ultrasound
Diagnostic
audible
infrasound
Sound
Compression and Rarefaction
–Sound waves require a _____
–They cannot travel through a _____
medium
vacuum
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)
sound longitudinal transverse parallel perpendicular
Sound
Wave Descriptors
–______
–_____
–_____
–_____
–Acoustic _____, a.k.a., propagation speed
–_____
amplitude frequency period wavelength velocity intensity
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
strength variable normal average minimum maximum minimum
Sound
Wave Descriptors – AMPLITUDE
Units are any unit of an acoustic variable
- -______ = degrees
- -_____= Pascal’s (Pa, MPa)
temperature
pressure
Sound
Wave Descriptors – FREQUENCY
- Number of ____ that occur in one second
- Determined by the _____source
- Affects _____and _____RESOLUTION
cycles
sound
penetration
axial
Sound
Wave Descriptors – FREQUENCY
____/____ = 1 Hertz
Humans are capable of hearing frequencies between _____- _____Hz = AUDIBLE SOUND
Frequencies > _____Hz = ULTRASOUND
Frequencies < _____Hz = INFRASOUND
cycle second 20 20,000 20,000 20
Sound
Wave Descriptors – FREQUENCY
Typical in Diagnostic Medical Ultrasound
__-__ MHz through __-__ MHz
Great penetration
Lousy _____resolution
Great axial resolution
Lousy _____
1 2 10 20 axial penetration
Sound
Wave Descriptors – FREQUENCY
Frequency (Hz) = 1/___ (sec)
_____and Frequency are RECIPRCALS
period
period
Sound
Wave Descriptors – FREQUENCY
Frequency INCREASES——–Period ________
Period INCREASES——–Frequency _____
Period and Frequency are _____PROPORTIONAL
decreases
decrease
inversely
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
lower
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
shape
lower
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
sinusoidal
linear
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 _____
tissue
frequencies
Sound
Wave Descriptors – FREQUENCY HARMONICS
Harmonics are ____ and odd multiples of the fundamental frequency
even
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 _____
frequencies
frequency
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)
spatial
width
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
time
time
sound
Sound
Wave Descriptors – PERIOD
Unit = _____, μs (microsecond)
Common US periods < 1μs
Period (ms) = 1/_____(MHz)
Period and Frequency are _____
second
frequency
reciprocals
Sound
Wave Descriptors - PERIOD
Period DECREASES——–Frequency _____
Period INCREASES——–Frequency _____
Period and Frequency are _____ PROPORTIONAL
increases
decrease
inversely
Sound
Wave Descriptors – Wavelength
_____ of space over which one cycle occurs
Determined by _____ source AND _____
length
sound
medium
Sound
Wave Descriptors – Wavelength
λ
Unit = _____, mm (any distance measurement)
1 mm = _____m
Common US wavelengths in soft tissue are:
_____- _____mm
meters
- 001
- 1
- 8
Sound
Wave Descriptors – Wavelength
Wavelength (mm) = _____ Speed (mm/μs)/Frequency (MHz)
λ = c/f
For Soft Tissue:
Wavelength = _____(mm/μs)/_____(MHz)
propagation
1.54
frequency
Sound
Wave Descriptors – Wavelength
If: λ = c/f
Then as:
Wavelength increases - Frequency ______
Wavelength decreases - Frequency _____
Wavelength and Frequency are
_____PROPORTIONAL
decreases
increases
inversely
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
speed
velocity
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
speed meters second medium 2 20
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
speed 1.54 1,540 1.54 3,500
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
chart
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
energy
strength
Sound - Propagation Media
What is it about the medium that determines propagation speed?
The medium’s
- -_____
- -Bulk Modulus
- -_____
- -_____
- -_____
stiffness
density
compressability
elasticity
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 _____
compression
density
matter
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
elasticity
compressibility
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 _____
increases decreases decreases decreases increases
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
frequency
wavelength
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
transducer
continuous
pulsed
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
transducer
transducer
charged
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
frequency period spatial pulse duty
Pulse Repetition Frequency
a.k.a.: PRF, Pulse Repetition Rate
Number of _____ that occur in one second
1 pulse/second
Units : _____
pulses
hertz
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
4,000
15,000
source
PRF
Pulse Repetition Frequency
a.k.a.: PRF, Pulse Repetition Rate
DEPTH
PRF depends on imaging _____
depth increases ⇒ PRF _____
depth is _____ proportional to PRF
depth
decreases
inversely
Pulse Repetition Frequency
a.k.a.: PRF, Pulse Repetition Rate
PRF = 1/___
PRF increases ⇒ PRP _____
PRF is _____ proportional to PRP
depth increases ⇒ PRP _____
PRP
decreases
inversely
increases
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
time
Pulse Repetition Period
a.k.a.: PRP
Units : seconds, micro-, milli-
Typical to clinical imaging: ___ – ___ ms
Determined by the _____
Can be changed by sonographer
0.07
0.25
source
Pulse Repetition Period
a.k.a.: PRP
DEPTH
PRP depends on imaging depth
depth increases ⇒ PRP _____
depth is _____ Proportional to PRP
increases
directly
Pulse Repetition Period
a.k.a.: PRP
PRP = 1/PRF
PRF increases ⇒ PRP _____
PRF is _____ proportional
decreases
inversely
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
time
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
0.1
1.5
source
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 _____
axial
depth
sonographer
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
increases
increases
directly
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
decreases
inversely
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
time
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
source
depth
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
increases
increases
directly
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
decreases
decreases
indirectly
Spatial Pulse Length
aka: SPL
_____ of distance a pulse occupies
_____ from the start of a pulse to the end of the pulse
length
distance
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
0.1
2.5
source
medium
axial
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 _____
cycles
wavelength
increase
increase
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
directly
decrease
indirectly
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
frequencies
unitless
Bandwidth
short pulse ⇒ ____ (large) bandwidth
long pulse ⇒ narrow (_____) bandwidth
short SPL ⇒ broad (_____) bandwidth
broad (large) bandwidth ⇒ _____Q factor
broad
small
large
low
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
purity
unitless
decrease
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
decrease
increase
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
long frequencies CW short shorter wide pulse
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.
sound
time
time
time
Frequency
Determined by the Sound Source
_____ (Hz, MHz) - Number of cycles per second.
Pulse Repetition Frequency, aka: PRF (Hz, kHz) - Number of _____ per second.
frequency
pulses
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.
sound
medium
length
length
