# Sampling the Wave Equation for String Vibration

Signal Processing Asked by Leonard on December 25, 2020

I am having a difficult time understanding the basic principles when sampling the function describing the vibration of a string. Mainly I am confused on given a sampling rate how many samples to take and what size the increments when sampling should be.

I am using the solution to the wave equation from this article (in german).
If my explanation is unclear let me know and I’ll try to give more information.

Assuming I understand the question correctly, you need to sample the string's position at least twice as fast as the maximum frequency you anticipate the string can move or the highest frequency you care about. So if the highest overtones the string produces are 16kHz, you need to measure at at least 32kHz if you want to be able to reconstruct the original motion faithfully. This is the Nyquist-Shannon sampling theorem and you can probably find several hundred descriptions of it here and elsewhere on the internet.

If you know the lowest frequency the string can produce or that you care about, there are other tricks you can do (look up heterodyne) to reduce your sample rate requirements assuming you have the equipment to do so on the analog side.

Answered by AnalogEE on December 25, 2020