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30 Cards in this Set
- Front
- Back
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In diagnostic sonography, sound pulses created by ...travel through ..., or .... |
a transducer biologic tissue media |
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All waves carry |
energy from one location to another. |
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Many different forms of waves exist such as |
heat light sound magnetic |
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Sound is a ... wave in which... |
mechanical particles in the medium move |
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The molecules in the medium... |
vibrate back and forth from a fixed position. |
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Sound cannot travel through... |
a vacuum; it must travel through a medium, where molecules are alternately compressed and rarefied |
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Compressed |
squeezed together |
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Rarefied |
stretched apart |
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Sound travels in... |
a straight line |
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Sound waves are ... waves. |
longitudinal waves |
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Acoustic propagation |
The effects of the medium upon the sound wave |
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Biologic effects |
The effects of the sound wave upon the biologic tissue through which it passes. |
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Sound waves are identified by |
oscillations in acoustic variables |
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Three acoustic variables |
pressure density distance *used to distinguish between sound waves and other types of waves |
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If one of the three acoustic variables has a rhythmic oscillation, then the wave is a |
sound wave |
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The wave is not a sound wave if... |
something other than pressure, density, or distance (particle motion) oscillates in a wave. |
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Pressure |
concentration of force in an area pascals (Pa) |
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Density |
concentration of mass in a volume (kg/cm^3) |
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Distance |
measure of particle motion cm mm |
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After a wave is identified as a sound wave, it is important to describe the wave's features using |
acoustic parameters |
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Acoustic parameters (7) |
Period Frequency Amplitude Wavelength Power Intensity Propagation speed |
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In a transverse wave |
particles move in a direction that is perpendicular to the direction that the wave propagates |
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Longitudinal waves |
particles move in the same direction that the wave propagates. *Sound is a longitudinal wave |
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A pair of waves are considered in-phase when |
their peaks (maximum values) occur at the same time and at the same location. Similarly, the troughs of the waves (minimum values) occur at the same time and place. |
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Interference |
More than one sound beam may travel in a medium and, on occasion, multiple beams may arrive at an identical location at exactly the same time. The waves lose their individual characteristics at that moment and combine to form a single wave |
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Both in-phase and out-of-phase wave pairs undergo |
interference; however, they combine differently |
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Constructive interference |
The interference of a pair of in-phase waves results in the formation of a single wave of greater amplitude than either of its components
resultant wave is larger than one of its components |
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Destructive interference |
The interference of a pair of out-of-phase waves results in the formation of a single wave of lesser amplitude than at least one of its components resultant wave is smaller than one of its components |
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Interference of waves with different frequencies |
At some moment in time, the waves are in phase and the interference is constructive, while at other moments, the waves are out of phase and the interference is destructive. |
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When the frequencies of the waves differ, |
both constructive and destructive interference occur |
