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67 Cards in this Set
- Front
- Back
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The features of a sound wave are described by what?
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Acoustic Parameters
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What is the ultrasound system and transducer called (in relation to sound waves)?
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Source
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What is the tissue through which sound travels called?
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Medium
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ACOUSTIC PARAMETER: the time it takes a wave to vibrate a single cycle or the start of one cycle to the start of the next cycle
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Period
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PERIOD: units?
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Time
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PERIOD: determined by source or medium?
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Source
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PERIOD: adjustable?
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No
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ACOUSTIC PARAMETER: the number of cycles that occur in one second
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Frequency
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FREQUENCY: units?
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Hertz (meaning per second)
1 cycle/sec = 1 Hz |
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FREQUENCY: determined by source or medium?
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Source
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FREQUENCY: adjustable?
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No
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Sound waves with a frequency < 20 Hz are called what?
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Infrasound
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Sound waves with a frequency between 20 Hz - 20 kHz are called what?
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Audible Sound
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Sound waves with a frequency > 20 kHz are called what?
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Ultrasound
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Name two ways PERIOD & FREQUENCY are related?
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1. Inversely Related
2. Reciprocals |
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Which three acoustic parameters describe the magnitude (size/strength) of a sound wave?
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Amplitude
Power Intensity |
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ACOUSTIC PARAMETER: the difference between the (minimum or maximum) value and baseline value
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Amplitude
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AMPLITUDE: units?
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Any of the acoustic variable units:pressure - Pascals (Pa), density - g/cm(3), or distance - cm
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AMPLITUDE: determined by source or medium?
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Both. Initally by the source
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AMPLITUDE: adjustable?
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Yes
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Difference between amplitude and peak-to-peak amplitude?
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Peak-to-peak amplitude is measured from trough to peak
Amplitude is measured from baseline to (trough or peak) |
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ACOUSTIC PARAMETER: the rate of energy transfer or the rate at which work is performed
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Power
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POWER: units?
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Watts / W
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POWER: determined by source or medium?
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Both. Initially by the source
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POWER: adjustable?
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Yes
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How are AMPLITUDE and POWER related?
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POWER is proportional to AMPLITUDE squared (if amplitude increases by a factor of 3, the power is increased 9-fold)
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ACOUSTIC PARAMETER: the concentration of energy in a sound beam; how the power in a wave spreads or is distributed
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Intensity
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INTENSITY: units?
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watts/square cm
W/cm(2) |
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INTENSITY: determined by source or medium?
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Both. Initially by the source
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INTENSITY: adjustable?
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Yes
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How is INTENSITY related to POWER?
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INTENSITY is related (proportional) to the POWER
(if power is doubled or quartered, the intensity is doubled or quartered) |
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How is INTENSITY related to AMPLITUDE?
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INTENSITY is proportional to AMPLITUDE squared
(if amplitude doubles, intensity increases by 4x) |
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WAVELENGTH: units?
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Length (mm, m, etc)
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WAVELENGTH: adjustable?
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No
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WAVELENGTH: determined by source or medium?
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Both
(Only parameter determined by both!) |
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What is the speed of sound in soft tissue?
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1.54 mm/microsecond
1540 m/s 1.54 km/s |
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ACOUSTIC PARAMETER: the distance or length of one cycle
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Wavelength
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What is the relationship between WAVELENGTH & FREQUENCY?
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Inversely Related
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How do you determine the wavelength of a wave through soft tissue?
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1.54mm / the wave's FREQUENCY
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What is the relationship between WAVELENGTH/FREQUENCY and imaging quality?
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Shorter WAVELENGTHS = higher quality images
Higher FREQUENCIES = higher quality images (remember: inverse relationship) |
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ACOUSTIC PARAMETER: the distance that a sound wave travels through a medium in 1 second
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Propagation Speed
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SPEED: adjustable?
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No
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What area of the body has the slowest sound propagation SPEED?
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Lungs: 500 m/s
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The relative weight of a material is called what?
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Density
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What area of the body has the fastest propagation SPEED?
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Bone: 3500 m/s
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What is the relationship between SPEED & density?
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Inversely Related
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SPEED: units?
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Distance / Time
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SPEED: determined by source or medium?
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Medium
(Only parameter determined by only by medium!) |
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What characteristics of a medium determine its SPEED of sound?
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Stiffness & Density
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The ability of an object to resist compression is called what?
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Stiffness
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Name the five parameters which are all initially determined by the source
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Period
Frequency Amplitude Power Intensity |
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Which parameter is determined by the medium?
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Speed
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Which parameter is determined by both source and medium?
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Wavelength
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T/F: a wave with a frequency of 15,000 MHz is ultrasonic
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T
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T/F: if the amplitude of a wave is increased to 3x its original value, the intensity is increased by 6x
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F
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T/F: if the power of a wave is halved, the intensity is reduced to 1/4 its original value
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F
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T/F: propagation speed increases as frequency increases
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F
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Medium 1 has a density of 9 and a stiffness of 6. Medium 2 has a density of 8 and a stiffness of 6. In which medium will sound travel slower?
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Medium 1
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Which of the following characteristics will create the fastest speed of sound?
A. high density, high stiffness B. low density, high stiffness C. high density, low stiffness D. low density, low stiffness |
B
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Which of the following characteristics will create the slowest speed of sound?
A. high density, high stiffness B. low density, high stiffness C. high density, low stiffness D. low density, low stiffness |
C
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T/F: propagation speed increases as frequency increases
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F
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T/F: propagation speed increases as frequency decreases
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F
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T/F: propagation speed does not change with frequency changes
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T
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What is the wavelength of 3 MHz sound in soft tissue?
A. 0.51 m B. 0.51 km C. 0.51 mm D. 0.51 nm E. 0.51 micrometers |
C
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What is the wavelength of a wave with an unknown frequency traveling in soft tissue?
A. 0.51 microseconds B. 0.51 m/s C. 0.51 pa D. 0.51 W E. 0.51 mm |
E
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The effects of sound waves on tissue in the body are called what?
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Bioeffects
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The effects of tissue on sound waves are called what?
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Acoustic Propagation Properties
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