Raleigh effect
The Raleigh coefficient describes the roughness of the seafloor. A rough seabed will scatter the signal and produce more specular echo's. Increasing returns lead to more phase comparisons and amplified amplitude detections. Compare the image below:
So:
rough seabed --> lower Raleigh coefficient --> more direct returns --> stronger amplitudes & more phase detections
smooth seabed --> higher Raleigh coefficient --> less direct returns --> weaker amplitudes & less phase detections
Multiples
Multiples have a longer two way travel time but also seem to arrive at random incidences at the transducer. This incoperates less ambiutiy for the phase detection. You'll notice that the phase detection becomes a bit contaminated when multiples are added.
