What is an echo?

Radio

Radio & Sound

Simply put, an echo is the reverberation of sound which, after a small gap of time, comes back to the listener. It is nothing but the reflection that takes place due to the sound waves hitting an obstacle.

The time gap between the original sound and its echo is because of the time taken for the sound wave to go and come back. In fact, bats use the concept of echoes to judge the distance of objects around them. Generally hard surfaces like mountains, walls etc. tend to produce echoes. The unit of measurement of an echo is decibels.

What is required for an echo to be audible?

Even though echo is an everyday phenomenon, we do not get to hear it often. This is because there are certain parameters which need to be in place for an echo to be audible. Some of them are à

  • Echoes occurring within one fifteenths of a second are indistinguishable to our ears. This means that taking sound velocity to be 343 m/sec and the normal temperature of the room to be 25 degree centigrade, it can be safely said that the reflecting surface has to be at a distance of 11.3 m or more for our ears to perceive an echo.
  • Quantity of sound hitting the object has to be sufficiently high to produce an echo properly.
  • The object needs to have an area large enough to produce an echo
  • All other sounds except the one forming the echo need to be absent.

Important uses of Echo:

While in most instances echoes are advantageous, in some cases like in telephones they create a lot of disturbance and are hence not desired. Some of the most important uses of echo area:

  • SONAR is a device used by ships, submarines etc. to detect objects and vessels either underwater or on the water as well as navigate in the seas with the use of echo. The time taken by the echo to come back is used to calculate the distance of the object from the vessel sending the echo.
  • Doppler ultrasound is a kind of test which is noninvasive and is done by using the concept of echo to measure blood pressure and flow. It is generally used to test conditions like heart diseases that are congenital or
    abnormalities related to the valves of the heart, bulging or blocked arteries, venous insufficiency etc.
  • Echocardiogram also uses the concept of echo to test the condition of a patient’s heart
  • Doppler RADAR beams a microwave signal towards a known target in order to get velocity data. It is used in meteorology, aviation, radiology etc.
  • In music echoes are used to give a haunting quality to the music created with the help of an Echoplex.

Echo is used to denote different things when used in different fields. In computer terminology echo is a command which prints or displays characters while in mythology, Hera, the wife of Zeus, cursed Echo, a nymph, so that she was only able to repeat what others had just said. This also gave rise to the term echo as it is used now.

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