pierrec 3 days ago

Having done a fair amount of audio physical modeling, I'll just say a synthesized version that's both fast and realistic would be possible but difficult. The difficulty is at least "it would make an impressive presentation at DAFx [1]", though I might be underestimating it, and it's more "you could make it your master's thesis at CCRMA [2]"

Ideal springs are a common, simple element in this field, but this kind of spring is very much not that.

You're probably better off improving the sample-based version by fading out the audio when necessary and using different samples based on the way it's triggered. If you have "ultra-dry" samples (maybe taken with a contact mic), you can add a convolution effect with a well-chosen impulse response, this will allow you to sharply cut off or adjust the audio and still have a natural-sounding tail.

[1] https://www.dafx.de/

[2] https://ccrma.stanford.edu/

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  • gregsadetsky 3 days ago

    I'm extremely grateful for this. My most deeply held secret is that I wish I could do this for a living - digitally modeling weird/beautiful objects/instruments and work on that forever haha. (And maybe make pedals out of them, I don't know)

    If you don't mind humoring me (I'm quite the novice in this field), if I automated the recording of "all" possible positions for a spring (say I had a motor positioned in a way that would let me pull the spring in any polar direction), would that make modeling potentially easier?

    There might be a "train an AI, here's 1000 recordings" angle, but I'm not necessarily interested in/asking about that.

    Just strictly for modeling, would it help the R&D phase to have a lot of high sample rate recordings? Thanks a lot!

    P.S. Also, if you have a good intro to DSP class/book, I'd love to hear it. I know about a few, but a recc is always appreciated

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    • pierrec 3 days ago

      That's funny, I was trying to do other stuff after posting my comment, but my brain kept working in the background, against my will, looking for the best approach to actually model this. Honestly, I was probably being pessimistic about the difficulty of a synthesized version, but I still think your current approach (don't synthesize, use samples) is more reasonable and can be made more responsive.

      I don't think that recording a large number of starting positions would help that much with creating a (non-ML) model, and I doubt a high sample rate would provide much useful information either. A more common approach would be to try getting separate sounds for the impulse and the resonant body, though they may be impossible to really separate, and the actual model may end up more complex than that.

      You probably have a good starting point already with your code for the animated model. I think the sound mostly comes from the collision between coils (collisions not visible in your animated model), and almost entirely from the lowest couple of windings that are against the wall. This is your impulse. The resonant body might be in 2 parts: the wall and the long end of the spring. Your existing model can tell you when to trigger the impulses, and how much force to put into them.

      For resources, one of my favorite intros to DSP is the one by Sean Luke: https://cs.gmu.edu/~sean/book/synthesis/

      I wrote my own intro to physical modeling, though it focuses on different instruments: https://www.osar.fr/notes/waveguides/

      Julius O. Smith has an encyclopedic amount of content on the topic, though it's often condensed into math that can be hard to apply: https://ccrma.stanford.edu/~jos/

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      • gregsadetsky 3 days ago

        I'm deeply, extremely, super duper grateful for all of this. Thanks a ton!

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