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.