The Dolphin Defender
Dolphins and Sounds

swimming dolphins

by Irene Tejaratchi

Dolphins use sound to detect the size, shape, and speed of objects hundreds of yards away. Fascinating and complex, the dolphin’s natural sonar, called echolocation, is so precise it can determine the difference between a golf ball and a ping-pong ball based solely on density. Although humans have researched these intelligent marine mammals for decades, much of their acoustical world remains a mystery.

One of the keys to dolphin echolocation is water’s superb conduction of sound. Sound waves travel 4.5 times faster in water than they do in the air. Dolphins use this to their advantage, in ways that would make a superhero envious. Using nasal sacs in their heads, dolphins send out rapid clicks that pass through their bulbous forehead, or “melon.” The sound is focused, then beamed out in front of the dolphin. The sound wave speeds through the water, bounces off the object under investigation, and is reflected back to the dolphin. Fat-filled cavities in the dolphin’s lower jaw receive this information and auditory nerves conduct it to the middle ear and brain, where an acoustic picture is created.

Scientists say that dolphins may also use clicking to communicate with one another. Although dolphins do not possess vocal cords, they still “speak” using sounds such as whistles, squeaks, and trills. A mother dolphin may whistle to her newborn for days, apparently to imprint a signature whistle upon her baby that will enable it to recognize her. It is believed that dolphins use whistles to identify one another and possibly for other functions, such as communicating strategic alerts while hunting in a group, but scientists have yet to crack the code. Many doubt, however, that dolphins have a formal language akin to that of humans.

In the 1950s, researcher John C. Lilly helped pioneer the systematic study of dolphin vocalization. A strong advocate of interspecies communication, Lilly wrote several books about dolphins, inspired the film Day of the Dolphin (1973), and was a supporter of the Marine Mammal Protection Act of 1972. Another pioneer of dolphin research, Kenneth S. Norris, first obtained evidence of dolphin echolocation by blindfolding a bottlenose to test its ability to locate an object underwater.

Since the 1960s, American military scientists have studied dolphins, and have trained them to perform such tasks as attaching explosives and eavesdropping devices to enemy ships or submarines. In the mid-1980s, the U.S. Navy began training dolphins to search for mines using their echolocation. In 2003, dolphins were deployed for the first time in a real war situation to probe the seafloor for mines near the Iraqi port of Umm Qasr. For decades, animal activists have opposed the use of dolphins for entertainment or military activities, citing questionable training methods and the stress-related illnesses, such as ulcers, that the animals can manifest in such situations.

Dolphin advocates also object to the navy’s use of manmade sonar, which is used to scan and investigate the ocean depths, claiming that it is harming dolphins and other marine mammals. They point to incidents such as the beaching of four different whale species off the coast of the Bahamas in March 2000, following navy sonar exercises in the area. Marine mammals strand themselves for a variety of reasons, but investigations confirmed that navy sonar caused the Bahamas stranding. Researchers are not exactly sure how manmade sonar affects marine mammals. Some believe the intense sounds may scare or disorient them and cause them to rapidly flee to the water’s surface, resulting in a sort of decompression sickness that damages sensory organs and causes internal bleeding.

If technological sonar can be implicated in the death of dolphins, it would be a tragic irony, considering that the sonar is based in part upon nature and dolphins’ superior echolocation capability. Efforts to replicate dolphin echolocation continue to fall short, as humans have yet to achieve the complexity and precision that 50 million years of evolution has bestowed upon dolphins. Perhaps if scientists could understand dolphin-speak they’d have more luck, but for now the true nature of dolphin communication remains mysterious.

  • Sakinah S.

    This article is informative. Dolphins are very social creatures, and gentle; they’re always helping humans. I hope that the military realizes the harm they’re causing by exploiting the dolphins, and stop misusing the gifts and intelligence of these beautiful animals.

  • Sharise R. Rizzo

    I am so glad to see and read this information about helping dolphins. I am looking forward to the program today and learning what I can do to help protect our precious ocean and dolphins. Thank you all for informing the world about our ocean and dolphins.

  • Zoe

    I saw the program The Dolphin Defender on PBS the other night. I felt really compelled to check out this website to see if there is anything I could do to help protect these beautiful and intelligent creatures from the cruelty of man.

  • Mikey

    Well, ok. Yeah, sonar testing is killing dolphins and whales, but it’s not like they’re not helping us. Dolphins have provided us with this excellent way of locating mines and other hazards underneath the oceans. I wish there was some way these dolphin deaths could be avoided, but please don’t act like sonar doesn’t help us humans. We probably will be able to win wars with this kind of unique and advanced technology.

  • Maria Senna

    Mikey, this kind of frivolous attitude towards wildlife is exactly what has gotten our planet into the terrible shape it is today.

    Judging from your post, you will probably think the earth is in perfect shape, but the science (I repeat – science) is out there for you explore the facts.

    Dolphin, whales and other marine life are critical beings in a what is a very complicated ecosystem. The removal of top predators such as these can usher in great imbalance and problems in our delicate ecosystem.

    Beyond the preservation of the planet, it would be nice if people cared that these great marine mammals are going extinct. It would be nice if people cared about other life (beyond their own).

    Don’t worry about winning some so-called hypothetical war with sonar…There are considerably stronger, more intelligent, more effective ways to stop war.

    If we’re going to live on this planet much longer, we have to start thinking less about war games, and more about life.

  • Maria Senna

    For those that care about life, and would like to take action, please see here this Save the Whales:

    More info for your edification: For those that care about life, and would like to take action, please see here:

    more info here:

  • franchesca

    I was looking at this website for educational reasons and found that this was a great example to the question of how are sound waves used by animals in technological devices. i also feel that we sound save these itellegent animals

  • Anonymous

    I was looking on the web trying to a find a few websites on how sound waves used by animals and in teconological waves and found the pefect one.

  • Jacob

    What do you mean “50 million years of evolution” – the dolphin echo-location transmission and reception system looks Designed. .an otherwise excellent article spoiled by evolutionary brain-washing. .

  • eleisa


  • asjia

    thanks for this informitave information it really helped me with my report and yes I gave credit where credit was do . ~A highschool student~ Nash central

  • Myleah

    The use of sonar may be hurting dolphins, which is sad; however, we are absent-mindedly hurting dolphins anytime we attend a show like those at Sea World. Dolphins use sonar in the tanks they live in. The waves will ricochet off the walls of the enclosed area, which causes a psychological disequilibrium. This makes the dolphins extremely ill and most will die as a result. In addition, dolphins have extremely sensitive skin. All of this combines to make dolphinsliving in captivity a very dangerous and thing. -Myleah

  • Induja Johal

    Simply, this put up is actually the sweetest on this deserving topic. I agree together with your conclusions and will thirstily look ahead to your forthcoming updates.

  • Chase Broddy

    It was so creepy and shocking. Goodness this makes me think if I’m going to buy a car not just twice but more than 10 times =( Or maybe those people just don’t know how to follow rules? But some of them are just plain accident. So we never really know. And by the way I stumble this good for share. Thanks ^_^

  • Noah

    Evolution can not make such a complex system or Creature. Every Creation has a creator Something does not come from nothing. Maybe you should teach more Godly Content as PBS is for children and you all should be ashamed of yourselves trying to teach children what you don’t know , by backing it up with millions of years.

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