EVERYTHING YOU NEED TO KNOW ABOUT ECHOLOCATION...
How Echolocation worksEcholocation is a method of using sound to locate and identify objects. Dolphins and bats are among some of the better known animals to use echolocation. Despite common belief, bats are not actually blind. They can actually see almost as well as humans. However, when they fly and hunt for insects in the dark and so must use echolocation to help them.
Echolocation works in the same way as sonar. While bats fly they will send out high pitched calls and listen to the echoes to create sonic map of the area and objects around them. Distance is measured by how long it takes for the sound to bounce back. The frequency of the calls is too high for an adult human to hear naturally, measuring at about 110 kHz, whereas the average range of Hz that human can hear is about 15-20 kHz. By using a range of frequencies, the bats can recognize an object and either avoid it as prey, or catch it as a predator Dolphins also use echolocation, but their calls are clicks. Each click lasts about 50-128 microseconds and range from about 40-130 kHz. The sound waves bounce off the objects in the water and return to the dolphin as an echo. Dolphins use a lower frequency than bats due to the fact that high frequencies do not travel far in water and they have a short wavelength and low energy. Dolphins are able to learn and recognize shape, size, speed, distance and direction and different echo signatures returned by their preferred prey species. Studies have shown however, that echolocation is more useful to a dolphin that uses it in tandem with sight- visually impaired dolphins take more time to echolocate and object. |
How the image is constructedA human creates sound by forcing air out of our lungs through our larynx, causing our vocal cords to vibrate as the air flows across them, producing sound. A dolphin does not have vocal cords in its larynx, so sound is most probably produces by the movement of air in the nasal passage, in a tissue complex called the ‘dorsal bursa’, which includes the ‘phonic lips’. These structures project into the nasal passage and as air pushes through here and past the phonic lips, the tissue around it vibrates and produces sound, which is transferred to the melon and then broadcasted. Dolphins can produce both clicks and whistles at the same time as they have two dorsal bursa complexes which can function independently and simultaneously.
After a dolphin has produced clicks to echolocate, it then needs to receive the sound. The main areas in which this is done are the fat filled cavities in the lower jaw bones. This connects to the dolphin’s middle and inner ears, which in turn connect to the hearing centres in the brain using the auditory nerve. Sound waves are received to the brain in the form of nerve impulses, allowing the dolphin to interpret the sounds that they hear to give them a visual image. Check out more at: https://www.youtube.com/watch?v=EFu_ef9XypY |
human echolocationDaniel Kish was born with bilateral retinoblastoma, retinal cancer, and he had both eyes removed by the time that he was 13 months old, leaving him blind. However, he has learned to ‘see’ using echolocation, producing clicks with his tongue and sending out bursts of sound which bounce off surfaces around him and are echoed back to him, allowing him to form a visual image in the visual cortex of his brain, and ‘see’ his environment. These sharp clicks travel at a speed of more than 300 metres per second and return to him at the same speed, though decreased greatly in volume.Although Kish is not the first blind person to use echolocation to see, he the only one that we know of who has mastered the technique and is able to teach it to others.
Despite the limitations, Daniel Kish shows that his ‘FlashSonar’ is actually, in some cases, far more effective than the visual input that we receive. His method of echolocation grants him a three hundred and sixty degree view of his environment, with it working almost as well behind him as it does in front. He can ‘see’ around corners and the sound also works through surfaces- it is, in a way, almost like having X-Ray vision. Check out his remarkable story here: https://www.ted.com/talks/daniel_kish_how_i_use_sonar_to_navigate_the_world/transcript?language=en#t-85264 |