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38 Cards in this Set
- Front
- Back
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wavelength (l)
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distance between one compression and one rarefraction
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frequency (f)
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Hertz, 1/s cycles per second determined by the sound source only
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period (t)
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seconds, time to complete one cycle
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Acoustic Velocity
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speed at which a wave travels through a medium
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attenuation
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amount of amplitude reduction as the wave travels
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average attenuation of US
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.8dB/cm/MHz
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3 components of sound waves
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longitudinal, mechanical, need a source
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Longitudinal waves
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particles vibrate in the same direction as the wave
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Transverse waves
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particles vibrate perpendicular to the wave
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Compression
Rarefraction |
pushes out
pulls in |
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propagation of sound
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how the sound energy is transmitted to the area remote of the sound source
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propagation of vibration
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depends on the sound propagation media
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Sound wave properties
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pressure, power, intensity, amplitude
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Specular Reflector
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an interface larger than the width of the beam
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Reflection
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all reflection in DMS depends on the acoustic impedance mismatch
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Acoustic Impedance
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how much a medium resists sound
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Impedance mismatch
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determines the amount of reflection that occurs
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diffuse reflection
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interface larger than the beam width
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scattering
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interface smaller than the beam width
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Reflectivity
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Acoustic impedance mismatch, angle of incidence, SST
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Snells Law
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Angle of transmission determines the resulting angle of incidence
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Diffraction
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ultrasound beam to spread out as the waves move farther from the sound source
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Interference
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con. and dest. waves running into each other
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Refraction
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a change in direction
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4 acoustic variables
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temperature, pressure, particle motion, density
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4 media characteristics
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elasticity, compressibility, density, bulk modulus
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Frequency of sound in DMS
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1.5MHz-10MHz
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Air, Water, Soft Tissue, Muscle, Bone
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330, 1480, 1540, 1580, 4080
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The FORCE particles experience
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Pressure
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Energy delivered to a specific area per unit time
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Intensity
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Total energy of the beam summed over the entire cross-sectional area
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Power
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Maximum variation that can occur between two acoustic variables
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Amplitude
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Med 1 is stronger than Med 2, so the beam bends TOWARDS normal incident
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Case 1
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Med 1 is slower than Med 2, so the beam bends AWAY from normal incident
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Case 2
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Med 1 is slower and the angle is less than 22 degrees and the beam shears away
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Case 3
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Mass per medium measures in volume
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Density
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How much the media volume decreases when pressure is applied
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Compressibility
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How resistant the medium is to change
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Bulk Modulus
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