Which factor can cause the propagation speed to change?

Which factor can cause the propagation speed to change?

• A. Moving from one tissue to another
• B. Changing the observer position
• C. Changing the source frequency
• D. Increasing distance traveled

Answer: (A)

Propagation speed is determined by the medium. Different tissues have different characteristic speeds, so when the ultrasound wave moves from one tissue to another, its speed changes accordingly. That’s why interfaces between tissue types affect how fast the wave travels, measurements of travel time, and the behavior at boundaries. Changing the observer’s position doesn’t alter the wave’s inherent speed in the tissue (it might change how you measure signals or angles). Changing the source frequency changes the frequency (and thus wavelength in the tissue) but not the speed itself in a given medium. Increasing distance traveled only means the wave has more distance to cover and more attenuation, not that its speed changes.

Propagation speed is determined by the medium. Different tissues have different characteristic speeds, so when the ultrasound wave moves from one tissue to another, its speed changes accordingly. That’s why interfaces between tissue types affect how fast the wave travels, measurements of travel time, and the behavior at boundaries.

Changing the observer’s position doesn’t alter the wave’s inherent speed in the tissue (it might change how you measure signals or angles). Changing the source frequency changes the frequency (and thus wavelength in the tissue) but not the speed itself in a given medium. Increasing distance traveled only means the wave has more distance to cover and more attenuation, not that its speed changes.