Ocean soundwaves could help stop tsunamis

Published in the Journal of Fluid Mechanics, the research describes how sound waves and surface gravity waves – which had previously been thought unrelated due to the disparity in their propagation speeds – can interact. Known as triad resonance, the process requires two acoustic waves and a single surface gravity wave.

By aligning the properties of the different waves correctly, the sound waves can be used to alter the dynamics of the ocean waves. As well as being used to reduce the wave power of a tsunami, the technique could also amplify wave power for enhanced clean energy generation. 

“Our study describes how these two wave types, which exist in parallel worlds, can nevertheless exchange energy when the right conditions mature,” said Dr Usama Kadri, reader in Applied Mathematics at Cardiff University and lead author of the study.

“This ‘conversation’ between acoustic waves and surface gravity waves is made possible by a unique three-wave interaction known as triad resonance. In theory, this process allows us to effectively control wave energy – either by reducing destructive waves like tsunamis or boosting ocean waves for renewable energy capture.

“This is important because it offers us a physics-based way to reduce tsunami energy, weakening them significantly, which is not possible with current methods like seawalls or warning centres.”

Dr Kadri has previously explored tsunami mitigation, including an investigation of the 2022 Tonga tsunami where he discovered natural acoustic-gravity interactions influence wave behaviour at an oceanic scale. Building on that work, he has now identified the practical tuning parameters that can be used to control those interactions, including wave frequency and amplitude. Water depth was also found to be a key factor, with shallower waters enhancing the ability of the sound waves to diminish wave power.

“Shallow water dramatically boosts energy transfer, aligning with where tsunamis become most destructive,” said Dr Kadri.

“This natural ‘sweet spot’ could simplify practical applications.”

The Cardiff team is also hoping their findings can help address current limitations in marine renewables, which lag significantly behind wind and solar. Existing technologies struggle to efficiently capture energy from ocean waves, especially in deep water. Amplifying surface waves could be a solution and the team is looking at a proof-of-concept to support its theory.

“Once lab validation is achieved, designing real-world scaled acoustic generators becomes an engineering challenge ‘only’,” said Dr Kadri.