Reflection
What type of reflection happens when sound wave hots a smooth large boundary?
Specular reflection
Refraction happens during what type of incidence?
Oblique incidence
What is attenuation?
The weakening of a sound wave
What is scattering?
a redirection of sound in many different directions when is hits a small interface
What are the 2 factors that contribute to attenuation?
Path length and frequency
What type of reflection occurs when a sound wave hits a large and rough boundary?
diffuse reflection
Refraction occurs when 2 media have different propagation speeds. true or false?
True
What are the 3 types of attenuation?
absorption, reflection and scattering
What type of scattering occurs when a structure is much smaller than the beams wavelength?
Rayleigh scattering
With diffuse reflection, should we expect strong echoes to return or weak echoes?
weak echoes. The sound wave goes out in many different directions, therefore, not all of the echoes are going to return to the sound source.
reflection only occurs if the media on both sides of the boundary have different ____.
acoustic impedances
What is snells law?
sin(transmission angle) = PS of medium 2
-------------------------- ------------------
sin(incident angle) PS of medium 1
Which frequency attenuates more, high frequency or low frequency?
high frequency
What is Rayleigh scattering proportional to?
frequency^4
If our frequency doubles, how does that affect Rayleigh scattering?
Rayleigh scattering will increase 16 times.
What is IRC and what is the typical percentage of IRC?
IRC- the percentage of the intensity that reflects back when the sound hits a boundary
IRC is typically less then 1%
If the new propagation speed is higher in the 2nd medium, will the angle be higher or lower?
higher
What are the units for attenuation coefficient?
dB/cm
What's a common example(structure) of Rayleigh scattering in the body?
Red blood cells
What is the formula for attenuation coefficient in soft tissue?
a.c. = 0.5 x frequency
Acoustic impedance is determined by the the mediums _______ and ________?
Density and propagation speed
neither, the new angle is the same
soft tissue, bone/air, muscle, and blood
Blood, soft tissue, muscle, and bone/air
True or false. High frequency sound scatters more in the body?
True. Scattering and frequency are directly proportional.
What is the half-value layer thickness?
That is the distance a sound wave travels until its intensity is half of its original intensity.