2006-6-24 14:07 Satisfactory AnswerFirst of all: what is a sound wave, the sound wave is the state of mechanical vibration of an object (or energy) in the form of propagation. Vibration is the back-and-forth motion of a mass of matter near its equilibrium position. For example, the drum surface is struck, it is up and down vibration, this state of vibration through the air medium in all directions, this is the sound wave (in general, people in the natural environment can hear and feel the sound waves are only known as sound waves).
When the vibration frequency is higher than 20KHz or more (or vibration frequency size of 16Hz), people in the natural environment can not hear and feel the sound waves are called ultrasound.
People usually call the vibration frequency less than 16Hz sound waves as infrasound (referred to as infrasound), while the vibration frequency greater than 20KHz or more is called ultrasound.
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Respondent: xuzhenji
Sonar is the acronym " SONAR" is the phonetic translation of the English acronym, where the full name: sound navigation and ranging, is a kind of use of acoustic wave propagation characteristics underwater, through electro-acoustic conversion and information processing, to complete the task of underwater detection and communication of electronic equipment. It has two types of active and passive, belonging to the category of acoustic positioning. Sonar is the use of sound waves in the water for underwater target detection, localization and communication of electronic equipment, is the most widely used in hydroacoustics, the most important kind of device.
Interestingly, sonar is not a human patent, many animals have their own "sonar". Bats use the larynx to launch 10-20 times per second ultrasonic pulse and use the ear to receive its echo, with the help of this "active sonar" it can detect very small insects and 0.1mm thick wire obstacles. Insects such as moths also have "passive sonar", and can clearly hear the ultrasound of bats from 40 meters away, and thus are often able to escape attacks. However, some bats are able to use high-frequency ultrasound or low-frequency ultrasound that is beyond the hearing range of insects, and thus the hit rate of capturing insects is still very high. It seems that animals engage in "sonar warfare" just as humans do! Marine mammals, such as dolphins and whales, have "underwater sonar," which produces a very specific signal to find food and communicate with each other.
Because low-frequency sound waves (infrasound) can also penetrate thousands of meters under the sea and get information about what's going on in the ground. Measurements and observations in the water have not yet been found to be more effective than sound waves. Therefore, usually the sound waves used in sonar are mostly infrasound waves