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38 Cards in this Set
- Front
- Back
- 3rd side (hint)
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density
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the concentration of matter
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acoustic variables
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pressure, density, temp, particle motion
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sound
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a form of energy, consisting of mechanically produced waves
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acoustic
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pertaining to sound
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mechanical
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relating to motion
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propagate
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disseminate, spread, transmit
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rarefactions
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regions of low pressure and density
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compressions
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regions of high pressure and density
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cycle
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one complete variation in pressure or other acoustic variables
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frequency
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the number of cycles in a wave that occure in 1 second
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Hz
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Hertz (one cycle per second)
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KHz
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kilohertz (1000 cycles per second)
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MHz
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megahertz (1 million cycles per second)
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period (T)
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the TIME it takes for one cycle to occur
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If frequency increases then period decreases
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wavelength
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the length of a cycle in space
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If frequency increases then wavelength decreases
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propagation speed
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the speed at which a wave moves through a medium
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propagation speeds are the highest in solids and lowest in gases
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Pulse repitition frequency (PRF)
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the number of pulses occuring in one second
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Pulse repitition period (PRP)
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the TIME from the begining of one pulse to the begining of the next one
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if PRF increases then PRP decreases
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Pulse Duration (PD)
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the time for a pulse to occur
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Duty Factor (DF)
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the fraction of time that pulsed ultrasound is on
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if pulse duration increases then duty factor increases
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spatial pulse length (SPL)
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the length of space that a pulse takes up
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units are mm
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Bandwidth
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the range of frequencies contained in a pulse
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stiffness
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the resistance of a material to compression
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attenuation
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indicates the strength of a sound
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amplitude
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the maximum variation that occurs in an acoustic variable
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intensity (I)
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the rate at which energy passes through a unit area
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power increases then intensity increases
area decreases then intensity increases units are mW/cm2 or W/cm2 |
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Attenuation (a)
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the weakening of sound as it moves
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Attenuation coefficient (ac)
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the attenuation that occurs with each cm the sound wave travels
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units are dB-decibles
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Perpendicular Incidence
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marks a direction of travel of the ultrasound wave perpendicular to the boundary
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impedence (z)
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determines how much of an incident soundwave is reflected and how much is transmitted
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units are rayls
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Inrensity reflection coefficient (IRC)
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the amount of sound that gets reflected
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IRC=Ir/Ii
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Intensity transmission coefficient (ITC)
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the amount of sound that is transmitted
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Oblique Incidence
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marks a direction of travel of the incident ultrasound that is NOT perpendicular to the boundary
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Refraction
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A change in direction of sound when crossing a boundary
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Scattering
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the redirection of sound in many directions
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Back scatter
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sound scattered back in the direction it came from
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Interface
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boundary between 2 tissues that have different acoustic impedences
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acoustic impedence
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how a tissue resists sound movement through it
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z=p x c
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