The ocean is a very noisy place. Just like ocean swell, sound waves travel far underwater. In fact, sound can travel up to five times faster and further through water than air, plus sunlight doesn’t penetrate very deep so many marine species use sound instead of vision as their primary sense.
Both whales and dolphins have expertly adapted to life under the waves – they produce a massive variety of different sounds and break a couple records in the process.
The blue whale and the fin whale are the two largest creatures ever to have lived on Earth. They both use low frequency sounds that can only be felt as vibrations by us humans, but can be heard thousands of kilometres away by other whales.
Male humpback whales sing the longest, most intricate songs of any species. They can sing for hours on end, but no one knows for sure the purpose of their beautiful songs. Dolphins and toothed whales use higher frequency sounds for echolocation that lets them get information about their surroundings and find food.Sperm whales produce the loudest sounds of any species and do so to locate their favourite food, squid.
Photo by V Mignon.
A couple hundred years ago, the only sounds in the ocean came from the life that lived there as well as natural ambient sounds, like rain, cracking sea ice, breaking waves, etc. But today’s world with our trade, travel and globalisation has changed this. Today, human activities have created a huge mess of underwater noise, to the extent that ocean background noise is now dominated by the sounds created by long-distance cargo ships. The noise from human ship traffic has doubled every decade since the 60’s creating noise pollution that has the potential to hinder important messages that whales, dolphins and other marine life need to communicate with each other.This underwater racket disturbs essential every day activities like feeding and breeding patterns, as well as causing some marine life to move away from their traditional migratory routes and important habitats.
Ocean exploration by the oil and gas industry is expanding as our demand for energy increases. During their exploration surveys, the ocean floor is blasted by highly powered air guns. The echoes and sound waves created off the ocean floor and the earth’s crust beneath it are recorded to try map out oil and gas reserves. The sound created by the blasts is on a similar level to that created by a military fighter jet and can travel as far as 4,000Km’s underwater.
Other sources of noise are military sonar, echosounders (a device used to determine the depth of water), offshore construction, marine windfarms, ocean floor dredging activities, among many others.Not only do all of these noisy activities present a high risk for whales anddolphins by drowning out their own communication channels and disrupting their lives, but noise can even cause them injuries, including stress, organ and hearing damage. It can even kill them.
Today ocean noise is globally recognised as one of the major threats to marine ecosystems, scientists and conservationists are working together to try to better understand its impact. Organisations such as Whale and Dolphin Conservation are raising the profile of these issues and calling on governments to protect the ocean and the wild creatures that inhabit it. The good news about noise is that once you shut down the source, it disappears almost immediately.