How do side imaging sonar returns differentiate between soft bottom and hard bottom compositions?

Soft bottom areas appear dark on the display, whereas hard bottom areas return a bright signal.

Modern sonar tools like side imaging provide immediate visualization of the lakebed composition by interpreting the strength of the signal return. When the sound wave encounters a soft bottom, such as mud or silt, the energy is largely absorbed, resulting in a dark visualization on the screen. Conversely, hard bottom materials, like rock, gravel, or firm clay, reflect the sound energy strongly back to the transducer, creating a bright visual return. This immediate contrast allows anglers to quickly confirm the existence of preferred structural elements like gravelly areas or hard-bottom protrusions that might be indistinguishable using older mapping technologies.