CS 472 Module 3: Standing Waves And Plucked String Synthesis

Module content developed by Professor Tralie. Module engine developed by Professor Tralie and Professor Mongan.

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Please watch the videos below, and click the Next button to continue when you're finished

Standing waves

Let's take a moment to think about the physics behind vibrating strings, which will motivate some of the design choices we make when trying to synthesize sounds that are more interesting than pure tones. What we find is that the string supports a so-called base frequency f0, and all of the integer multiples of that frequency. Fractional multiples of that frequency do not resonate, and they die out quickly, as explained in the video below

A Standing Wave Experiment

Now that we have a rough idea about the math, let's look at an experiment that shows how a string supports a base frequency and its integer multiples

Plucked string

So in the above video we see that a string held down at two ends supports "wavelengths" (physical length of repetition of the pattern on the string) that are integer divisions of the length between the two ends. The longest wavelength corresponds to the base frequency and shorter wavelengths corresponding to the integer multiples of that frequency. But what actually happens when a string is plucked? Well, as it turns out, many of these wavelengths are present, and they all go at once. What we find over time, though, is that the higher frequency ones die out more quickly. Have a look at this slow motion video of a plucked string to see this