Sonar and ecjolocation
Like all wave, a sound wave doesn't just stop when it encounters an obstacle in its path or reaches the end of the medium, a sound wave will undergo certain behaviors when it encounters the end of the an obstacle medium. Possible behaviors include diffraction around the obstacle, reflection off the obstacle, and transmission (accompanied by refraction) into the obstacle or new medium.
Reflection of sound waves off of surfaces can lead to one of two phenomena which is a reverberation or an echo. A reverberation often occurs in a small room with width, height, and length dimensions of about 17 meters or less. You are probably wondering why the magical 17 meters? The effect of a particular sound wave upon the brain experiences more than a tiny fraction of a second. The human brain contains a sound in memory for up to 0.1 seconds. If a reflected sound wave reaches the ear within 0.1 seconds of the initial sound, then it seems to the person that the sound is prolonged. The reception of multiple reflections off of walls and ceilings within 0.1 seconds of each other causes reverberations - the prolonging of a sound. Since sound waves travel at about 340 miles per second within room temperature, it will take about 0.1 seconds for a sound to travel the length of a 17 meter room and back, causing a reverberation. This is why reverberations are common in rooms with dimensions of about 17 meters or less. For example, maybe you have observed reverberations when talking in an empty room, when honking the horn while driving through a underpass or highway tunnel or when singing in the shower. In auditoriums and concert halls, reverberations occurs and leads to the displeasing garbling of a sound. |
SonarSonar is simply making use of an echo. When a machine or animal makes a noise, it then sends sound waves into the environment around it. Those waves bounce off nearby objects, some of then objects reflect back to the object that made the noise. For example, it is those reflected sound waves that you hear when your voice echoes back to you from a canyon. Specialized machines and whales can use reflected waves to find distant objects and sense their movement and shape. The range of minimum frequency sonar is extraordinary. Another example, whales and dolphins can tell the difference between objects as small as a BB pellet from 15 meters away, and they use sonar much more than sight to find their families, food, and direction.
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echolocationEcholocation is the production of sound used for communication. Echolocation is the use of ultra-high frequency sounds for navigation and locating prey. For example, marine mammals and bats are able to use sound to "see". It is the returning echoes that give the animal an "image" of some parts of its environment.
But the echoes must be loud enough to return to the animal and short enough so that the echo of the sender returns back to the human or animal before the next one is sent out. Echolocation is usually used by mammals like whales, bats, or dolphins, whales. Humans have also learned this ability to communicate with their environment when they can not see. |