SONAR and Echoes

Also called

sonar · echo · echoes · reflection of sound · echolocation · ultrasound · depth of the sea · bat and moth · speed of sound · distance = speed × time ÷ 2 · sound navigation and ranging · reverberation · ship sonar · प्रतिध्वनि · सोनार · पराश्रव्य ध्वनि

Topics

• An echo is sound reflected back from a large hard surface such as a cliff, a wall or the seabed.
• To hear a distinct echo the reflected sound must reach the ear at least 0.1 s after the original.
• At 344 m/s in air, sound must travel 34.4 m there and back, so the surface must be at least 17.2 m away.
• SONAR (Sound Navigation And Ranging) sends ultrasound pulses into water and times their echoes.
• Distance = speed of sound × time ÷ 2, because the pulse goes down to the object and back again.
• Sound travels at about 1500 m/s in sea water, much faster than in air.
• Ships use SONAR to measure depth and to find wrecks, rocks, submarines and shoals of fish.
• Bats send out ultrasound squeaks and use the returning echoes to find insects in the dark.
• Ultrasound has a frequency above 20,000 Hz, too high for human ears to hear.

About this model

A GLB file of about 298 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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