Physics 2

If the boundary between two media has irregularities (with a size similar to or a bit smaller than the pulse's wavelength), then the wave may be chaotically redirected in all directions

Reflections from a smooth reflector (mirror) are specular and return in one direction.

If a reflector is much smaller than the wavelength of sound, sound is uniformly distributed in all directions (omnidirectional). Higher frequency sound undergoes more Rayleigh scattering. A red blood cell is a Rayleigh scatterer.

In soft tissue, the attenuatio coefficient (dB/cm) is approximately one-half of the frequency (MHz).

0.5dB/cm/MHz