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What is Sonar? - Definition, Uses & Examples

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  • 0:00 What Is Sonar?
  • 0:47 Active and Passive Sonar
  • 2:01 Sonar in the Animal Kingdom
  • 2:57 Lesson Summary
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Lesson Transcript
Instructor: Sergey Segal

Sergey has a Masters in Biomedical Engineering and has taught science and mathematics courses at the University of Wisconsin-Madison.

Sonar is a commonly used technique for communication, detection of objects, and navigation. Learn more about it by exploring its definition and some examples. Then, test your knowledge about sonar with a quiz.

What Is Sonar?

Have you ever wondered how sound can be used to detect distant objects? Let's start with some background information. You can think of sound as vibrations of molecules that propagate through a given medium. For example, humans and animals can hear a dog's bark because the bark produces disturbances in the air molecules around it that end up reaching the ears. Just as sound can travel through air, it can also propagate through water or other transmission media.

Sonar is a way of communicating, navigating, and detecting objects by using sound propagation. For the remainder of this lesson, we will focus on underwater sonar, which is used by submarines and some aquatic animals to perform the previously mentioned tasks.

Active and Passive Sonar

Sonar can be categorized as being active or passive. Active sonar involves the transmission and reception of sound waves. For example, when a submarine is used to map the topography of the ocean's floor, it sends out sound pulses, often referred to as pings, towards the bottom of the ocean within its vicinity. As these sound pulses travel downwards, they will encounter physical features such as hills, valleys, and rocks. The sound pulses are subsequently reflected back up towards the submarine, having been modified by the objects along their path. The reflected pulses are often called echoes. Receivers on the submarine that detect these echoes can then reconstruct the topography of the region from which the echoes bounced off.

Since the speed of sound in water is known, the distance to an object can be calculated by measuring the time it takes a given pulse to reach the object and be reflected back to the receiver. Passive sonar involves only listening to sound pulses from other entities. For instance, a submarine can detect enemy submarines by listening to pulses emitted within its vicinity. Often unintentionally, ships and submarines emit noise via their engines and other devices, which can be detected by passive sonar.

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