Statistical Math Question


    Mar 17 2006 | 12:08 am
    Hi, I am using the last outlet of fiddle~ to get out freq/amp pairs of individual sinusoidal components in this case of saxophone multiphonics. I would like to get an 'average frequency and amplitude' for each component over an adjustable period of time say 15 seconds or 2 minutes. However, my rudimentary math skills are leaving me quite baffled. I know it's not as simple as sticking a mean object on each component as high-frequency jumps skew the results and I am looking for some waiting of each frequency reported based on its amplitude. Basically, if I were to play a single multiphonic for 20 seconds, I would like to know what were the, say 7, strongest frequency areas and their relative amplitudes. Like an averaged sonogram but in numbers.
    Thanks in advance, Justin Yang

    • Mar 17 2006 | 12:19 am
      Here's part of the patch.
    • Mar 17 2006 | 1:06 am
      I'm not quite sure this answers your problem but one statistical formula you might find useful is the running average. Now, I'm not sure exactly what you mean by high frequency jumps skewing results and weighting based on amplitude so the formula below doesn't address that.
      Running average = x * alpha + ((1 - alpha) * previous running average)
      As you can see, it's a form of simple feedback algorithm where you plug the result of the equation back in. Alpha is a value between 0 and 1. Lower values mean longer averaging times. If alpha = 1, no averaging is done. This is also useful for smoothing data -- i.e. getting rid of spikes. See patch below.
      Jean-Marc
    • Mar 17 2006 | 1:20 am
      Btw, the slide object in MaxMSP 4.5 does this with user settable constants for positive and negative deltas (rise and fall).
      -Joshua
    • Mar 17 2006 | 2:54 am
      this should be simple.
      i usualy make fiddle~s output a signal first. to flatten the intonation line you can now use lowpassfilters, or slide~, or rampsmooth~. to control what happens just connect a cycle~ and listen to it.
    • Mar 17 2006 | 10:04 am
      On 17-Mar-2006, at 2:06, Jean-Marc Pelletier wrote: > Running average = x * alpha + ((1 - alpha) * previous running average)
      lp.stacey does this automatically. Give her an initialization argument specifying how wide your window is (10 data points, 20 data points, whatever) and she'll do the math. Follow the URI below to the Litter Starter Pack for more information.
      I'd give you an example but I don't have fiddle~ installed on this machine yet.
      -- Peter
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