Algorithm to change an already sampled guitarstring to sound like it was a bit damped by the hand

Question

I'm trying to simulate the damping of the hand on a guitarstring on an already recorded/sampled open guitarstring sound. I've been trying to use low pass filter and had a moving frequency range but that didn't make it sound like a damped string, just the loss of higher frequencies.

Could someone help me find good material on this, that a human could atleast grasp a bit? It's going to be implemented in C++ and I have been searching and found almoust everything about the karplus-strong string algorithm, but that's not what I want.. I do want the damping part implemented on a sample of an already recorded real played string.

Answer 1

This probably not as simple as you think. It is not just the right filter, but also the sound will decay faster. This is likely differrent for different frequencies.

If you have guitar at your disposal, you could measure the sound spectum over time when you strike it normally, and once while you dampen it. You can measure the difference in the initial spectrum as well as the difference in decay rate.

You can apply this information to the sound you want to alter, but you'd need to convert the signal to frequency-vs-time first.

But this may be far too complicated for what you had in mind. A simpler approach could be to first increase the decay, by multiplying the signal by e^(w*t), with w as the decay rate. You could split the signal in low and high pass signals and apply different decay rates, with the high freq component getting a faster decay.