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

Properties of Sound Waves

Sound

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

Sound-Propagation Media

Acoustic Velocity Equation

Sound Transmission

compression
rarefation
longitudinal
transverse

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Sound

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

wave

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Energy

Mechanical:
____ waves
_____waves
_____waves

Electromagnetic:
_____waves
_____
_____waves

ocean
seismic
sound
radio
x-rays
light

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Sound

General
Sound is a particular type of wave

Quantities of these variations are called acoustic variables

______
_____
_____Motion
_____

Density
pressure
particle
temperature

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Sound

Valuable Advice – Acoustic Variables

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

Density
pressure
particle
temperature

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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

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Sound

Compression and Rarefaction

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

oscillate

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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

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Sound

Compression and Rarefaction

–Sound waves require a _____

–They cannot travel through a _____

medium

vacuum

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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

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Sound

Wave Descriptors

–______

–_____

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

–_____

amplitude
frequency
period
wavelength
velocity
intensity

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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

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Sound

Wave Descriptors – AMPLITUDE

Units are any unit of an acoustic variable

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

temperature

pressure

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Sound

Wave Descriptors – FREQUENCY

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

cycles
sound
penetration
axial

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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

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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

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Sound

Wave Descriptors – FREQUENCY

Frequency (Hz) = 1/___ (sec)

_____and Frequency are RECIPRCALS

period

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Sound

Wave Descriptors – FREQUENCY

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

Period and Frequency are _____PROPORTIONAL

decreases
decrease
inversely

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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

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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

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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

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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

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Sound

Wave Descriptors – FREQUENCY HARMONICS

Harmonics are ____ and odd multiples of the fundamental frequency

even

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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

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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 0. 001 0. 1 0. 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