SPI- interaction of sound and media questions with answers

Attenuation CORRECT ANSWERS: Its the decrease in intensity, power and amplitude and the sound wave travels through a medium. Is attenuation related to the propagation speed? CORRECT ANSWERS: NO! because although the sound wave in becoming weaker it is still traveling in the same medium therefore the propagation speed (C) remains constant. What are the three components of attenuation? CORRECT ANSWERS: 1. Absorption ( when the energy is turned into heat) 2. Scattering (when the sound travels in all different directions) 3. Reflection (when the sound bounces off of a reflector and the transmission portion is weaker) What is the major portion of attenuation? CORRECT ANSWERS: Absorption is the main cause of attenuation. When you are talking about attenuation what are the units? CORRECT ANSWERS: The units are dB, and because it is getting weaker and not stronger the unit would also be negative, but if negative is not a choice then you need to chose the positive of the correct number. What situations cause more attenuation? CORRECT ANSWERS: The deeper the image, and the higher the frequency. What situations cause less attenuation? CORRECT ANSWERS: The shallower images, and the lower the frequency. List the attenuating structures from greatest to lowest amount of attenuation. CORRECT ANSWERS: Air, lung and bone, soft tissue, and bone. Why is bone cause the most attenuation? CORRECT ANSWERS: It causes the most attenuation because it absorbs 99% of the energy transmitted into the body. Reflection CORRECT ANSWERS: happens when propagating sound energy strikes a boundary between two media and some returns to the transducer. Specular Reflection CORRECT ANSWERS: This is when there are reflections from a smooth reflector (mirror) are specular and return in one direction, and they occur when the wavelength is much smaller then the irregularities in the boundary. Occurs when it hits the boundary at 90 degrees. Diffuse reflection or Backscatter CORRECT ANSWERS: this is when there are reflections in all different directions. Its caused when there is a rough boundary with irregularities that are the same size as the wavelength causing there to be disorganized and random back scattering.