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ECHO - PHYSICS PowerPoint Presentation
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  1. Sound By AthiraAnand

  2. Examples of situations in which echo is produced : • If you shout near a mountain, you are able to hear yourself again a little later  this sound which repeats itself is called an ECHO. Well, the question is how is it produced? Where is it coming from? Let’s See…

  3. Sensation of sound persists in our brain for 0.1 second. • To hear a distinct echo, the time interval between the original sound and the reflected sound should be at least 0.1 second. If (at 22°C in air) : Speed = 344 m/s, then the sound must go to the object and reach back the ear of the sender on reflection after 0.1 second. So now, the distance covered by the sound (from the point of generation to the reflecting surface and back) is: Distance = speed x time = 344 m/s x 0.1 s = 34.4 m Thus, from this calculation we can understand that: For hearing distinct echoes, the minimum distance of the obstacle from the source of the sound should be 17.2 m.

  4. An echo is the reflection of sound waves off of a surface which then bounce back to the sender. Echoes can often be heard in a gym, in a canyon or a concert hall. The sound waves must have some object to bounce off of. An echo is a loud sound reflection that arrives late and so is heard as a separate sound source. • Echoes can sometimes be heard in large concert halls, for example. Sound takes a long time to travel from the stage to the rear wall of the concert hall, if a strong reflection comes back from the rear wall to the front of the hall, this can be heard as an echo. To prevent this problem, it is common to apply diffusers to disperse the sound. Another common place to hear echoes is in some railway stations, making announcements hard to understand. • The term echo also refers to the physical sending back of sound or other waves and the repetition of sound by reflection.

  5. Normally, we hear an echo once, but there are chances where the echoes may be heard more than once. This is due to the successive or multiple reflections. Ex: During thunder, multiple echoes are heard because of the successive reflections of sound from a variety of reflective surfaces (the clouds and the land)