Echolocation

An Educational Resource on the Application of Sound Waves in Echolocation

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What is Echolocation?

Echolocation is a method of navigation for animals such as bottlenose dolphins and bats. It is considered as one of the most advanced sonar systems of the world. The term "sonar" stands for "sound navigation and ranging". It is a technique used to identify and recognize objects located, typically, underwater. Sonar systems radiate sound waves, which reflect off an object or signal, and returns to the sonar system, where the echo of the soundwave is interpreted. Sonar systems are used to map out sea floors, navigating torpedoes, submarine navigation, fishing, ultrasound, and are also used by animals. Bats and bottlenose dolphins are one of the many animals, which use sonar waves to replace their poor eyesight. How can echolocation exactly be used to replace eyesight? (Dolphin Encounters, 2008) (Seaworld.org, 2013)(Encyclopædia Britannica, 2013)(WiseDude.com, 2006)

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TASK: How Does Echolocation Replace Eyesight?

Remember: You may search the question number of the question you are answering in order to find the posts, where you can find out the answer in the search bar :) 1. Describe the process of a wave being reflected off an object in steps. Identify how energy is involved in the steps. 2. What is the difference between an echo reflected by a flat and smooth surface and a soft or curved surface? 3. Predict how the density of an object may affect how we may receive the echo bounced off the object. 4. How can blind people use echolocation? What kind of sounds do they make, and why? 5. List 5 uses for echolocation, and explain why they use echolocation. 6. Why should there be more research on echolocation? 7. Why are higher frequencies preferably used for echolocation? 8. Explain the characteristics a surface should have in order to create the most effective (most concentrated) echo in water. Consider volume & frequency of the original sound, texture and shape of the surface. Bonus Question Why do sound waves travel faster in water than in air? Mention how energy is transferred differently in the two media.

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Introduction to the Process of Echolocation

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WAVE PROPERTIES The type of wave, which is involved in echolocation are sound waves. This means they are a type of longitudinal or compression wave. In a longitudal wave, energy is therefore transported across particles in a chain reaction manner. This means when one particle is disrupted, it collides with the nearest particle, until the energy has arrived to a certain destination. (The Physics Classroom, 2013)

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WHY DO ANIMALS USE HIGH FREQUENCY CLICKS FOR ECHOLOCATION? WARNING this audio file may hurt your ears if you are using earphones, due to the high frequency of the sounds recorded. Higher frequencies are used in order to detect objects at a distace range of 5 to 200m, they travel faster than lower frequencies, and transmit less energy than lower frequencies. Clicks are simply more effective than using whistles or howls, because their echoes are simple and therefore easier to interpret. (Dolphin Encounters, 2008) (Seaworld.org, 2013)

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Process of Sending/Receiving an Echo

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FACTORS WHICH MAY AFFECT THE REFLECTION OF SOUND When a sound wave is reflected more than 0.1 seconds after the original sound was heard, it is considered an echo. When a sound wave hits a medium it is partially reflected off of the medium, and is partially transmitted across the surface of the medium. How much of the sound wave is reflected and transmitted depends on the structure, texture, and other qualities of the medium. Flat surfaces/ planes reflect a sound wave in the same angle size as the angle the sound wave met the surfaces medium. (see left, Figure 1) Curved surfaces may reflect sound in such a manner, that the sound waves either disperse or focused to a focal point. In the focal point, the largest amount of sound and energy is concentrated. (see Figure 3 & 4) The texture of the medium also affects the reflection of a soundwave. For example, an uneven, rough surface may cause the sound waves, hitting the surface, to reflect into many different directions. (see right, Figure 1 & 2) The structure and density of a medium is also a factor, which plays a role in the reflection of soundwaves. The softer a material may be, the more alike it is to the density of air or water. Therefore it is more likely to absorb sound waves. The harder a material is, the larger the portion of the sound wave is reflected. Little of the soundwave is most likely to be absorbed. (The Physics Classroom, 2013)

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WHY SHOULD THERE BE MORE RESEARCH ON ECHOLOCATION? Echolocation, or other similar processes which include using sound waves in order to identify certain surfaces, enable us to discover media, which we could not have through eyesight. Due to the possiblity to see without eyesight through echolocation, more research should be initiated on echolocation. Research on animals who use echolocation may benefit those who had lost their eyesight, and enable them to lead a normal life again. Blind people often use canes for echolocation, in the future, however, they can soon be trained to use echolocation without a cane. (see video) Another reason in order to research on echolocation is so that we can improve driving security. In the future, cars may be programmed to use high frequency clicks to detect whether someone is about to crash.

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How do humans benefit from echolocation?

Besides benefitting marine and nocturnal animals, echolocation can benefit humans. Sonar systems enable us to identify faraway objects underwater, or in the dark. -They can be used for communication purposes where a signal is sent to a certain destination, with a receiver. The destination, after interpreting the signal, can return the signal to the source of the signal. There, a receiver can decipher the signal. -Military uses include submarine navigation, underwater surveillance,detection of torpedoes, and detection of mines. -Sonar systems can also aid navigation for divers, or mapping of the seafloor. -Sonar systems are also used for medical puposes such as detecting diseases with ultrasound. -Blind people who rely on hearing and touch, use a cane or clicks to interpret their surroundings. (Encyclopædia Britannica, 2013)(WiseDude.com, 2006) (hawaii.edu, n.d.)

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Reference List

Dolphin Encounters, 2008. Dolphin Sounds. [Online] Available at: http://www.dolphinencounters.com/family-dolphinsounds.php [Accessed 5 May 2013]. Encyclopædia Britannica, 2013. Sonar. [Online] Available at: http://www.britannica.com/EBchecked/topic/554214/sonar [Accessed 5 May 2013]. Fontenelle Nature Association, 2004. Bat Echolocation Experiment. [Online] Available at: http://kindernature.storycounty.com/display.aspx?DocID=20097271336 [Accessed 11 May 2013]. hawaii.edu, n.d. Echolocation : Communication of Marine Mammals, Bats, and Humans. [Online] Available at: http://www2.hawaii.edu/~zinner/101/students/YvetteEcholocation/echolocation.html [Accessed 11 May 2013]. Mc Graw Hill Education, n.d. Search Results: Reflection of sound. [Online] Available at: http://www.accessscience.com/search.aspx?topic=PHYS:ACOU&term=Reflection+of+sound [Accessed 20 May 2013]. RichardDevine, 2012. Bat Recordings - with the Anabat SD2 - Ultrasonic Echolocation Detector. [Online] Available at: https://soundcloud.com/richarddevine/bat-recordings-with-the-anabat [Accessed 20 May 2013]. Seaworld.org, 2013. BOTTLENOSE DOLPHINS - Communication & Echolocation. [Online] Available at: http://www.seaworld.org/animal-info/info-books/bottlenose/communication.htm [Accessed 5 May 2013]. sensorwiki, 2011. Ultrasound. [Online] Available at: http://www.sensorwiki.org/lib/exe/fetch.php/sensors/ultrasound_echo_ranging.jpg?w=&h=&cache=cache [Accessed 20 May 2013]. Souza, G., 2007. Ben Underwood Intro VIdeo. [Online] Available at: http://www.youtube.com/watch?v=XUXh-X1iveU [Accessed 20 May 2013]. splashmaritime, 2009. Index of /Marops/data/text/Radartex/Radartex_files. [Online] Available at: http://www.splashmaritime.com.au/Marops/data/text/Radartex/Radartex_files/ [Accessed 20 May 2013]. The Physics Classroom, 2013. Reflection, Refraction, and Diffraction. [Online] Available at: http://www.physicsclassroom.com/Class/sound/U11L3d.cfm [Accessed 20 May 2013]. The Physics Classroom, 2013. Longitudinal Wave. [Online] Available at: http://www.physicsclassroom.com/mmedia/waves/lw.cfm [Accessed 21 May 2013]. weloveteaching, 2012. Index of /0sci208/lectures/waves. [Online] Available at: http://www.excellup.com/classnine/sciencenine/Image_sound/soundBoard.GIF [Accessed 20 May 2013]. WiseDude.com, 2006. Echolocation in Bottlenose Dolphins. [Online] Available at: http://www.wisedude.com/science_engineering/echolocation.htm [Accessed 11 May 2013].