Kongsberg Simrad MF90, Installation Manual

Page: 76 / 426

74
476671/B
Reverberation
When you transmit an acoustic pulse into the water to search for a target, echoes will also be
returned from any other objects in the beam. The energy reflected from these "unwanted"
objects is referred to as
reverberation .
Reverberation is generated when the echoes from your transmissions are reflected not only
by fish and valid targets in the water, but also from the sea bottom and the sea surface.
Reverberation is often regarded as noise.
There are several types of reverberation.
Volume reverberation
The volume reverberation is caused by minute plankton and air-bubbles in the water.
This reverberation has often daily cycles in intensity.
Surface reverberation
The surface reverberation depends on the weather condition and the waves.
Bottom reverberation
The bottom reverberation depends on the roughness and physical properties of the
sea bottom.
Reverberation is often a limiting factor, especially if you are searching for smaller targets.
The echoes from the bottom will always depend on the sea bottom properties. How uneven
the seabed is will affect the echoes. What kind of bottom you have under your vessel is
also significant, as rock, mud or sand will provide different reverberation. The bottom
reverberation usually makes it difficult to investigate targets located close to the seabed.
Your current tilt setting will also have an effect on the reverberation. The echoes from the
sea surface will vary with the current sea state and your current tilt setting.
The illustration demonstrates how the sea bottom and the sea surface return echoes back to
your sonar system.
Simrad MF90 Installation Manual