Scattering

Scattering of sound occurs when the sound interfaces with small interfaces or rough boundaries.

Scattering differs from specular reflection in several key ways.  Unlike specular reflection, scattering:

• generates weaker echoes

• is angle-independent

• is frequency-dependent

A good example of a scattering medium is blood.  The red and white blood cells in blood are tiny, and as a result, they scatter the incident sound in all directions.  Only the small fraction that is backscattered returns to the transducer in the form of an echo.  Using a low-frequency transducer, arterial blood typically appears anechoic because the scattered echoes are too weak to be displayed.  However, if a higher frequency transducer is used, the backscatter increases, the scattered echoes become stronger and may be visible on the screen.

This short 2-minute video explains that concept: