Facts about echoes (acoustics)

  • If a person shouts at a solid stone wall, his words often come back to him. He hears them as an echo.
  • Echoes occur when sound waves strike a hard, smooth surface and are bent back. Sound can be reflected from a wall just as light can be reflected from a mirror. A rough surface breaks up the sound waves.
  • In a valley where mountains are all around, a sound may be echoed many times.
  • Some places are famous for their echoes. In one place in Ireland 100 echoes of a bugle note have been counted.
  • To experiment with echoes, a person should be at least 60 feet away from the wall he is sending the sound against. If he is any closer, the echo comes back so soon that it gets mixed up with the original sound.
  • "A duck's quack doesn't echo" is a much-quoted scientific myth. The truth is that a duck's quack does, in fact, echo; however, it may be difficult to hear.

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