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Asked by 10yling to Ed, Hayley, Jason, Nathan, Sophie on 10 Mar 2013. This question was also asked by lauraquinn12.
Question: To a fish, what does humans sound like underwater?
- Keywords:
- fish,
- human,
- ocean,
- sound,
- underwater
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Sophie Holles answered on 10 Mar 2013:
What is the human doing? If the human was in the water swimming, the fish might be able to hear the ‘swimming sound’ of bones moving against each other! If the human was driving a boat, or a ship, the fish would hear an engine sound, but to you what the fish hears would sound something like a train in a tunnel, because fish only hear the lowest frequencies (the deeper tones). If the human was building a windfarm (something that is happening quite a lot around the UK at the moment) it would sound like massive very deep thumps as the construction workers hammer piles into the sea bed. If the human was diving they would hear the bubbles. When they are drilling the seabed for oil or gas they also make mechanical noise..
There are so many human noises in the ocean at the moment that if all the human activity stopped, the ocean would take about 18 days to go quiet because of all the echoes! Most of it sounds like engine noise, clanging and thumping, and its all the bassy tones because that’s how fish’s ears work.
- Keywords:
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Edward Bovill answered on 12 Mar 2013:
Fish hear things very differently from humans. For fish, sound waves are travelling through water as opposed to air and as sound travels through water about five times the speed it does in air sounds will be distorted. If you’ve ever tried to shout to a friend underwater in a swimming pool you’ll know what I mean.
Fish also have two different ways of ‘hearing’ sounds.
1) They have two inner ears very similar to ours, which allows them to hear most sounds in the water, but, unfortunately for them, they cannot pinpoint where the sound is coming from like we can. This is because most fish are the same density as water and so sound passes straight through them. Because sound travels so fast underwater (five times faster as I’ve already said) and their inner ears are so close together, they cannot tell where the noise is coming from.
2) They can also sense sounds through their lateral line. The lateral line is a line of specialist microscopic organs running down the middle of each side of a fish which allows them to sense changes in pressure in the water within a short distance of their bodies. This allows them to hear very deep noises but also allows them to move with such precision when in a big school of fish.
So, in summary, we would sound distorted and they wouldn’t know where we are unless they could see us.
Comments
thecoolboys commented on :
Hello, why do you want to see whether fish hear us swimming when there are so many other things in science to do??
luvinscience1202 commented on :
I feel we should know if they can hear us swim because it can lead us to a new era, it could change the way we deliver packages over sea or have holidays on sea could be a bad idea, this is my answer to your comment, thanks, 😉
Sophie commented on :
The important thing is to do something you love and feel passionate about because that’s what you’ll do best at. There are lots of things you can do in science that are worthwhile so everyone should chose what’s best for them. Personally I think its important to look at how humans are affecting the environment because we can’t survive without it. You could think of the earth as our space ship so we have to keep it well maintained. Fish hearing a human swimming was just a silly example, but fish could use swimming sounds to avoid predators for example, to escape an approaching shark. Humans making lots of noise in the water might stop fish from being able to hear approaching predators. A huge number of people in the world depend on fish as their primary source of protein so we should care about their survival for food and economic reasons, as well as their value as a part of biodiversity.
It is a really good question though and all scientists should ask themselves what is the point of what they are doing to make sure it is worthwhile!
cardinal commented on :
that is so cool i want to do that some time.
Sophie commented on :
Sorry Edward you’re not totally right!
Edward’s point about directional hearing in fish is an opinion I have met but I don’t believe it to be true. There are many experiments where fish have been proven to be able to find the source of a sound. The particles in an underwater sound wave are moving as vectors (in lines back and forwards as they vibrate) and fish can follow the vectors to the source of the sound. Here is a published experiment where they demonstrated this: http://jeb.biologists.org/content/215/1/152.short These fish use sounds to find a mate, so they would be pretty stuck if they couldn’t work out where the sound was coming from!!
In my own work I have done experiments where fish respond with directional behaviour to sound: when you play larval coral reef fish the sound of a coral reef, they swim towards it. This is really important to know about because larval fish live out in the open ocean but they have to find a habitat to settle on so they can metamorphose into adult fish and reproduce. Light doesn’t travel very well underwater but as sound travels much better, they use the sound of a reef to find habitat to settle on! I did an experiment that showed that when boat noise is played at the same time as reef noise, the directional behaviour is disrupted and less fish find the reef. Fish being able to find the habitat they want to live on is important for the survival of coral reefs and also for all the people that eat the fish.
Fish have incredible temporal resolution in their detection of sound, which means that they can detect the difference between two sounds that happen very close to each other in time. One of the ways we think they can find out what direction a sound is coming from is by the echoes bouncing off their swim bladder and back to their ears!
Sounds also would not sound distorted to them. They sound distorted to us because our ears are designed for working in air, but fish are very well adapted to detecting and interpreting sound underwater.