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  • Dynamic Noise Filter Questions

    The Dynamic Noise Filter refers to a low frequency filter frequency that is raised when the music has high frequencies. Question, what is the nominal value of the low frequency filter without any changes ? For example, when the threshold is NOT reached , what is the filter's low frequency value ?.

    Also, the help file talks about a 6 dB or 12 dB filter shape. Where is that set ?

    Marc

  • #2
    The Dynamic Noise filter uses a set of variable frequency tracking filters. Their quiescent low frequency is the setting that you choose in the filter frequency field. I do not remember the filter order that we decided to use - probably 1st or 2nd order. When in normal mode (non-enhancer) signals are attenuated below the threshold setting of the chosen frequency. In enhancer mode, signals are amplified when they occur above the threshold setting. An interesting combination (sort of a push-pull dynamic noise filter) can be had by placing two in the multifilter with one operating in normal (noise reduction) mode and the other operating in enhancer mode. Signal attenuation or amplification are calibrated in dB by way of the HF gain control.

    Craig
    Last edited by Craig Maier; 02-02-2015, 10:52 PM.
    "Who put orange juice in my orange juice?" - - - William Claude Dukenfield

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    • #3
      Craig,

      Thanks, that helps. Thus, the frequency that is entered is BOTH the low pass value if the input is below the threshold AND its the hi pass filters value that sends in the signal that is used as a gate.

      Let me know if I have it correct.

      Marc

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      • #4
        Hi Marc,

        Yes, sort of. It does not operate as a gate, but the resultant signal is proportional to the measrued level above the threshold setting. It does not "switch" so to speak.

        Craig
        "Who put orange juice in my orange juice?" - - - William Claude Dukenfield

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        • #5
          The more that I thought about it, the more I seem to recall that we use a 1st order as one side of the equation and a 2nd order for the other side. I forget which is which, however.

          Craig
          "Who put orange juice in my orange juice?" - - - William Claude Dukenfield

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          • #6
            Craig,

            You are correct that the "gate" term isn't correct. More like it passes the energy along...

            It's an interesting filter and it seems to have a long history in the world of noise suppression.

            Marc

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            • #7
              Marc,

              Yes, the amount of energy passed on to the output is proportional to the excitation signal and its overall gain is set by the "HF Gain" setting (in dB). This idea has been around for a long time; our implementation of it may be unique, however. We did not look at what "the other guys did" before creating the filter.

              Craig
              "Who put orange juice in my orange juice?" - - - William Claude Dukenfield

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