Propagation speed less than that of soft tissue will place reflectors too:

When the propagation speed of ultrasound in a medium is less than that of soft tissue, the interpreted position of reflectors within the imaging system is affected. Specifically, sound waves travel slower through the medium, which causes the ultrasound machine to misjudge the depth at which the reflectors are located.

This occurs because the ultrasound machine calculates depth based on the assumption that the speed of sound is consistent with that in soft tissue (approximately 1540 m/s). If the propagation speed is slower, the time it takes for the echoes to return is longer than the machine anticipates. Consequently, the system interprets the echoes as coming from a deeper location than they truly are, resulting in the misplacement of reflectors deeper within the image.

Understanding this concept is crucial for sonographers as it impacts image accuracy and diagnostic quality in various imaging situations.