Interaction of sound & mediaCh 6 & Range equation Ch7 Flashcards
Method of rating numbers. The numbers of 10’s that are multiplied to create the original number
Logarithm
The strength of sound beams and brightness of images are measured in this unit
Decibel
Reports relative changes and is a ratio with two intensities starting level and actual level
Decible notation
3db
double
-3db
half
10db
ten times larger
-10db
one tenth
6db
four times larger
-6db
one fourth
Two factors that determine attenuation
Path length and frequency of sound
How are distance and attenuation related?
Directly
How are frequency and attenuation related?
Directly
Is decibles relative or absolute change?
Relative
Is attenuation relative or absolute change?
Relative
longer distance
more attenuation
higher frequency
more attenuation
Shorter distance
less attenuation
lower frequency
less attenuation
Process that contribute to attenuation
Reflection, scattering, and absorption
Reflection in only one direction with a smooth boundary
Specular reflection
Irregular boundaries reflection that radiates in more than one direction
Diffuse reflection or backscatter
Random redirection of sound in many directions
Scattering
How are scattering and frequency related?
directly
Scattering when the structure’s dimensions are much smaller than the beam’s wavelength . Scatters the sound wave in equally in all directions.
Rayleigh Scattering
Which scatter results with an organized boundary?
specular or Rayleigh scatter
Which scatter results with an unorganized boundary?
Diffuse or scattering
Whats the significance of attenuation in diagnostic sonography?
Higher frequency produce shorter waves which create more accurate images. However higher freq attenuates more and is less capable of traveling far or deeper.
When ultrasound is converted into another energy form like heat.
Absorption
How are absorption and frequency related?
Directly
The number of db of attenuation that occurs when sound travels one cm db/cm
Attenuation coefficient
The constant value for the attenuation coefficient
2db/cm