Humans invented the sonar system through bionics. Sonar is a transliteration of the English abbreviation "sonar", and its full name in Chinese is: acoustic navigation and ranging. It is an electronic device that uses the propagation characteristics of sound waves under water to detect, locate and communicate underwater targets through electro-acoustic conversion and information processing. There are two kinds, active and passive, which belong to the category of acoustic positioning. Sonar is a widely used equipment in hydroacoustics. It was invented by Lewis Nixon of the British Navy in 1906. The first sonar instrument he invented was a listening device, which was mainly used to detect icebergs. This technology was applied to the battlefield during World War I to detect submarines hidden underwater.

In the study of dolphins, scientists found that dolphins rely on echolocation to prey, and can even stun their prey with loud noise. Dolphins use ultrasonic waves with frequencies above 200-350 kHz for "echo location", and communication between dolphins uses sound waves to transmit information in seawater. Dolphin calls are low-frequency sounds that dolphins communicate with each other. Dolphin sonar has a high sensitivity. It can find a metal wire with a diameter of 0.2 mm and a nylon rope with a diameter of 1 mm several meters away, can distinguish two signals with a time difference of 200 burs, can find fish schools hundreds of meters away, and can walk through a pool full of bamboo poles flexibly and quickly blindfolded without touching. Dolphin sonar has a strong "target recognition" ability, which can not only identify different fish and distinguish different materials such as brass, aluminum, bakelite and plastic, but also distinguish the echo of its own voice from the sound waves played back by the person who recorded its voice. The anti-jamming ability of dolphin sonar is also amazing. If there is noise interference, it will increase the call intensity over the noise so that its judgment will not be affected. And dolphin sonar also has the ability to express feelings. It has been proved that dolphins are animals with "language", and their "dialogue" is carried out through their sonar system. In particular, among the four remaining freshwater dolphins in the world, the most precious baiji in the middle and lower reaches of the Yangtze River in China has a clear "division of labor" in its sonar system, which is used for positioning, communication and alarm, and has a special function of phase modulation through frequency modulation.