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Speed

Speed

May 09, 2012

Shea says this:

  • Sound travels 1130 ft/second in air at room temperature

  • Much slower than the speed of light, as we all know

  • Hammer a nail or hit a golf ball at a distance, we see and hear that the sound comes later

  • That is, reality is out of sync!

  • Filmmakers force into sync sounds that in reality would be late.

  • Generally, film and television sound should be in hard sync with the picture, despite the effects of the speed of sound

  • Speed of sound dependent on the medium: faster in denser media

  • Faster in water than in air

  • Faster in steel than in air (that's why we listen to the steel rail to hear when the train is coming)

  • What happens in a large theatre during the time it takes for sound to reach the audience?

  • Most of us can easily see when film is two frames out of sync

  • Pull up the sound by one frame in motion picture release prints, so the sound comes early

  • In a large theatre the film will be out of sync for some, in sync for others