Below is an animation of an ideal stretched string, such as a guitar string

• The left termination is moved upward at a constant velocity.
• The right termination is rigid.
• Information always travels at a fixed speed c on the string.
• Applied force is proportional to string slope. See how it rises in steps.
• Below the physical string animation is a digital waveguide view using force waves.
  • Top delay line carries right-going traveling force waves.
  • Bottom delay line carries left-going traveling force waves.
  • Color intensity is proportional to force (or string slope).
  • Physical force is given by the sum of the traveling-wave components.
  • Note that there are only one or two forces (slopes) on the string at any moment.
  • A velocity-wave simulation is similar, except there are sign inversions at each end. As a result, the physical string velocity only alternates between zero and the velocity of the left termination. You can see this in the animation as well.

Slower version