Awaken your senses – Why is it so noisy underwater?
Go diving they said, find peace and tranquility floating weightless in the quiet and beautiful ocean! And then when i went it wasn’t quiet!!!
There are all sorts of noises down there. Some obvious like a boat passing by and it’s easily distinguishable engine sound, but what are all the other strange noises I can hear?
So underwater noises can come from a huge range of sources, both man-made and natural.
As divers know, sound travels much more efficiently underwater than it does in the air, it travels over 4 times faster due to the molecules being closer together so energy passes from one to another more quickly. This speed also makes it difficult for us to easily distinguish from which direction the sound is coming.
So what are the snapping, crunching, grinding, clicking, popping and scraping sounds we may hear?
If you are diving then you will be able to hear your bubbles as they pass by your ears, and maybe the breathing and bubbles of your buddy, who should be close by! Hopefully you aren’t hearing constant noise from another divers noise maker, and only hear this when there is something you need to pay attention to!
Wave action and the motion of the ocean all mean that substrate, rocks and sand are constantly being moved around on the ocean floor all that movement produces sound.
It is estimated that 300-500 species of fish actually make noise, although a lot of these may be outside of the hearing range of humans. These noises are, like land animals, thought to deter predators, warn others of danger and also to attract mates. One of those sounds may be coming from parrotfish as they use their powerful beak-like teeth to crunch off parts of corals which contain their food source.
Fish are thought to make noises in 3 main ways, hydrodynamically or in other words by quickly changing speed and direction, stridulating which means they are rubbing body parts together and also by vibrating/drumming.
Hydrodynamic sound production
As an object moves through the water, the water is compressed and moved which produces sound. Some shrimp can make a whip-like snapping sound using their oversized claw, sounding like rice krispies when you put the milk in. Spiny lobsters can also make a sound by wiggling their antennae which causes a squeaky rasping sound.
Different species use different body parts such as fins, spines and even skeletal bones to make noises such as the northern seahorse that rubs its skeletal bones together. Grinding of teeth, especially when feeding, produces noise like the parrotfish we’ve already commented on.
Swim bladders are gas filled chambers used to help in buoyancy control that fish can use, by contracting muscles around them, to produce sound. Squirrel and Soldier Fishes, red-coloured fish found under overhangs and in shady cracks, can produce a grunting sound when approached by vibrating their swim bladders. This is thought to warn off predators.
Grunts, a common sight at our dive sites here, often in big schools, surprisingly make a grunting sound. They do this by grinding their pharyngeal teeth near the back of the throat and using the swim bladder to amplify the noise.
And listen out for the Sergeant Majors low frequency sound that the male uses to attract a mate and that apparently can be heard by divers if you listen carefully.
Another amazing sound you may be likely to hear if you come diving or snorkeling here is:
We are blessed here in Costa Rica to have a very long Humpback Whale season because we get a migration of the Northern Humpback population from Dec to April and then another season, this time of the Southern Humpbacks from July to Nov.
It’s amazing to hear the wide range of sounds that these majestic animals can make and to share that while under the water. There are whistling noises, and moans, grunts, blasts and squeaks, some which seem like an ongoing song, a family conversation or just a very squeaky door opening. Humpback song is described as one of the most complex songs in the animal kingdom, and despite the fact they may be a long way away from us when we hear them, it’s a very special experience that you never forget!
Come dive with us, awaken your senses and listen to the underwater world.