US Vocabulary
Terms
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- Pressure
- Concentration of force in an area (units = pascals)
- Density
- The relative weight of a material
- Distance
- Measure of particle motion (units = cm, feet, mile)
- Transverse Waves
- Particles move in a direction that is PERPENDICULAR (at right angles) to the direction that the wave propogates
- Longitudinal Waves
- Particles move in the same direction that the wave propogates
- In-Phase Waves
- When peaks (maximum values) occur and the same time and at the same location
- Out-of-Phase Waves
- When peaks (maximum values) occur at different times and so do their troughs
- Constructive Interference
- Resultant wave is larger than its components
- Destructive Interference
- Resultant wave is smaller than one of its components
- Period
- The time it takes a wave to vibrate a single cycle
- Frequency
- The number of events that occur in a specific duration of time
- Amplitude
- The "bigness" of a wave
- Power
- The rate of energy transfer
- Intensity
- The concentration of energy in a sound beam
- Wavelength
- The distance or length of one complete cycle
- Propogation Speed
- The distance that a sound wave travels through a medium in one second
- Stiffness
- The ability of an object to resist compression
- Pulse Duration
- The actual time from the start of a pulse to the end of that pulse
- Spatial Pulse Length
- The distance thta a pulse occupies in space from the start to the end of a pulse
- Pulse Repetition Period
- The time from the start of one pulse to the start of the next pulse.
- Pulse Repetition Frequency
- The number of pulses that an US system transmits into the body each second
- Duty Factor
- The percentage or fraction of time that the system is transmitting a pulse
- Intensities
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Spatial - refers to space
Peak - maximum value
Average - middle value
Temporal - refers to time
Pulsed - transmit time only - Beam Uniformity Coefficient
- Describes the spread of a beam in space
- Attenuation
- Weakening of a sound beam in intensity, power and amplitude
- Amplification
- Strengthening of a sound beam
- Decibel Notation
- Standard measurement tool used to report changes in two intensities
- Logarithms
- A novel method of rating numbers, which represents the number of 10's that are multiplied to create the orignal number.
- Reflection
- The portion of a sound beam that is redirected back to the source after striking a boundary
- Specular Reflection
- The sound beam is reflected in only one direction in an organized manner after striking a smooth boundary
- Diffuse Reflection
- The sound beam is reflected in many directions after striking an irregular surface (backscatter)
- Scattering
- The random redirection of sound in many directions
- Raleigh Scattering
- A special form of scattering that occurs when the structure's dimensions are much smaller than the beam wavelength
- Absorption
- US energy is converted into another energy form, such as heat
- Attenuation Coefficient
- The number of decibels of attenuation that occurs when sound travels one centimeter.
- Impedance
- The acoustic resistance to sound traveling in a medium, measured in rayls
- Half-value layer thickness or penetration depth
- The distance sound travels in a tissue that reduces the intensity of sound to one-half its original intensity
- Three Types of Angles
-
Acute - less than 90 degrees
Right - equal to 90 degrees
Obtuse - greater than 90 degrees - Normal Incidence
- The incident sound beam stikes a boundary at exactly 90 degrees
- Oblique Incidence
- The incident beam striks a boundary at any angle other than 90 degrees
- Incident Intensity
- The sound wave's intensity immediately before striking a boundary
- Reflected Intensity
- The sound wave's intensity after striking a boundary that returns back in the direction from which it came
- Transmitted Intensity
- The sound wave's intensity after striking a boundary as it continues forward
- Intensity Reflection Coefficient
- Percentage of the intensity that bounces back after striking a boundary