Which statement is true about listening time relative to imaging depth?

Which statement is true about listening time relative to imaging depth?

• A. It decreases with depth
• B. It remains constant
• C. It increases with depth
• D. It fluctuates randomly

Answer: (C)

Listening time grows with imaging depth because echoes take longer to travel to a reflector and back the deeper the target is. In tissue, sound speed is about 1540 meters per second, so the round-trip time is roughly t = 2d / c. Deeper reflectors yield longer return times, so the system must listen for a longer interval to capture those echoes. That’s why listening time increases as depth increases. The other possibilities don’t fit because deeper targets don’t return echoes sooner, the time window isn’t fixed, and the return time isn’t random—it rises predictably with depth due to the constant propagation speed in tissue.

Listening time grows with imaging depth because echoes take longer to travel to a reflector and back the deeper the target is. In tissue, sound speed is about 1540 meters per second, so the round-trip time is roughly t = 2d / c. Deeper reflectors yield longer return times, so the system must listen for a longer interval to capture those echoes. That’s why listening time increases as depth increases. The other possibilities don’t fit because deeper targets don’t return echoes sooner, the time window isn’t fixed, and the return time isn’t random—it rises predictably with depth due to the constant propagation speed in tissue.