What are Echoes?

You must have tried to shout your name out loud in the empty school building and heard the name calling you back. When you visit the Ajanta and Ellora caves in Maharashtra and call out your name, it comes back at you. This phenomenon is called echo. These echoes are produced due to the bouncing of sound on solid surfaces.

An echo meaning is that it is a kind of sound that occurs due to the reflection of sound waves. The sound waves produced from a certain source bounce off from smooth and hard objects. It is just like a tennis ball that bounces off a wall. 

Echo

Sound Reflection

• Sound is produced due to vibrations from an object. It can be due to beating an instrument or an object or from the voicebox of animals.

• The speed of sound is 343 m/s.

• The direction of the sound changes after it bounces off a surface. But interestingly, the echo is exactly the same as the original sound. 

• Echoes are heard in enclosed spaces with hard and tough walls such as wells, caves, or large auditoriums. 

• The sounds may not always get reflected when the sound hits a soft surface like a cloth, cushion, or rubber. 

• The sound gets absorbed in those surfaces, and hence echoes don’t form. 

• Sound waves are vibrations produced by various objects and animals. 

• The light gets reflected on shiny surfaces, and the reflection of sound is very similar to it. 

• Just the reflecting surfaces are hard and solid in case of sound. 

• For the proper reflection of sound, the surface needs to be large and can be either rough or polished.

• The sound waves also follow laws similar to the laws of reflection of light.

Uses of Echo in Daily Lives

• The stethoscope uses the principle of reflection of sound. The thin film vibrates by the sound of the heartbeat and that vibration through the tubes to the earpiece makes us hear the heartbeat clearly. 

• Sonar is used to find objects and fishes under the sea. 

• High-frequency sound waves are released under the sea and when hit any object and reflect back the time required by the sound waves to return measures the distance.
  
  

The Reflection of Sound Waves

Examples of Echo

• A very common example of echo is what happens when we shout our names in a well or in mountains. 

• Dolphins also use sound waves to navigate their way. 

• The stethoscope that doctors use to listen to our heartbeats uses the principle of reflection of sound. The thin film vibrates by the sound of the heartbeat, and that vibration is reflected through the tubes to the earpiece making us hear the heartbeat clearly. 

• Sonar is a device that produces high-frequency sound waves under the sea water and when they hit any object and reflect back the time required by the sound waves to return and measure the distance.

Summary

In the case of an echo, the direction of sound waves might change, but the echo will sound exactly the same as the original sound. Bats fly in the night and release some special kind of sound waves that hit a surface and echo back allowing them to fly away from obstacles. The calls from an average bat can reach up to 130 decibels.

It is interesting to know that some animal sounds do not produce any echo and it's still not clear why such as the dogs barking and ducks quacking.