Researchers conducted experiments to study how waves change as they move across a sloping beach. They looked at how wave characteristics like frequency and time are affected by the sea bed shape. The experiments showed that as waves move towards the shore, the width of the wave spectrum decreases more slowly. They also found that the relationship between wave heights and periods changes as waves approach the shore. By developing a mathematical model based on their findings, researchers were able to predict how wave heights and periods change in the surf zone.