properties of sound 2
Terms
undefined, object
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- Attenuation, definition
- is the weakening of a sound wave as it travels through the medium, decrease in intensity, power, and amplitude
- State the relationship between attenuation and distance
- direct, as path length increases, attenuation increases
- State the relationship between attenuation and frequency
- direct, as frequency increases, attenuation increases
- reflection, definition
- occurs when a portion of the wave's acoustic energy is redirected back towards the transducer when the sound strikes a boundary, it weakens the sound beam
- two forms of reflection are
-
specular- when the boundary is smooth, the sound is reflected in only one direction in an organized manner
non-specular (diffuse or backscatter)- random reflection in multiple directions, from sound reflecting off irregular surface - rayleigh scattering, definition
- occurs when the structure's dimension are much smaller than the beam's wavelength, it scatters the beam equally in all directions-ex RBC
- state the relationship between rayleigh scattering and frequency
-
direct, as frequency increases rayleigh scattering increases
-rayleigh scattering=frequency to the fourth power - defintion of absorption
- occurs when US energy is converted into another form of energy-like heat or mechanical vibration of intercellular particles
- state the relationship between absorption and frequency
- direct, as frequency increases absorption increases, in soft tissues 80% or more of total attenuation is caused by absorption
- which form of reflection is the stongest, but is not reflected back towards the transducer?
- specular reflection
- definition of impedence
- it is the acoustic resistance to sound traveling through a medium
- what is the unit of impedence and its mathematical equation?
-
RAYLS (Z)
impedence=density x speed
impedence is calculated not measured - impedence is the property of what only?
- the medium
- state the relationship between density and impedence
- direct, as density increases impedence increases
- state the relationship between speed and impedence
- direct, as speed increases impedence increases
- state the definition of normal incidence
- occurs when the sound beam strikes a boundary between different tissues at exactly 90 degrees
- state the definition of oblique incidence
- occurs when the sound beam strikes a boundary at angle other than 90 degrees-can be acute or obtuse
- what is refraction?
- change in direction of wave propagation when traveling from one medium to another, if the medium doesn't change then there is no refraction-therefore if incidence or speed doesn't change then no refraction
- rayleigh scattering
- rayleigh scattering
- specular reflection
- specular reflection
- non specular reflection
- non specular reflection
- normal incidence
- normal incidence
- oblique incidence
- oblique incidence
- refraction
- refraction
- period
- period
- frequency
- frequency
- amplitude, compression and rarefaction
- amplitude, compression and rarefaction
- wavelength
- wavelength