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Stereo Tool 7.83 - Help - Noise removal

Noise removal section

Removes background noise, including 16-bit quantization noise.

The noise gate removes background noise, which is mainly useful for older recordings. But even for recent CD's it helps to let it work very gently, because quantization noise (the number of bits on a CD is not infinite) can be increased a lot by processing which makes music sound harsh. Gentle Total noise level and Noise gate level per band solve this.

Noise gate panel

General Noise Gate settings

  • Enabled
    Turns the Noise Gate on.

Total noise level panel

Global control of how much noise is removed.

  • Total noise level
    The maximum amount of noise to be removed.

    This can be fine-tuned for different frequency ranges in Noise gate level per band.

Noise gate level per band panel

Fine-tuning of the amount of noise to be removed per frequency range.

  • Band {} noise level
    The maximum amount of noise to be removed per frequency range, relative to Total noise level.

FM Hiss (removes FM hiss from INPUT signal!) panel

Removes FM stereo hiss on the input (!) signal.

If you need to rebroadcast audio from another radio station, and reception is not optimal, this filter can remove the FM stereo hiss without touching the rest of the sound. The sound stays stereo. Even quite severe stereo hiss can be nearly completely removed.

Settings panel

Settings that control the FM Stereo Hiss filter's operation.

  • FM median pos: Ordered histogram position that determines noise level
    Controls hiss vs. tone detection.

    A lower value means that sounds are more easily detected to be noise - a too low value will reduce not only stereo hiss but also other stereo sounds.

    A higher value means that even hiss is not detected properly anymore, and noise removal will not work at all anymore.

    Hint: Use the Difference checkbox to hear if what is removed is really only the stereo hiss.

  • Multiply median at most with
    Controls hiss vs. tone detection in combination with Multiply median at most with.

    Higher values mean that sounds are more easily detected as noise.

  • Reduction strength of estimated FM hiss level
    Determines how much FM hiss can be removed, compared to the measured hiss level.

    This normally needs to be set a bit above 100%, because otherwise the hiss is not always completely removed. If it is set too high, other sounds might be damaged as well.

  • History size (Response speed)
    The amount of time that hiss detection uses.

    If this time is short, FM stereo hiss will be removed nearly immediately when it becomes present. However, the detection of noise vs. tones and the level detection is less accurate. With longer times, it takes longer for the filter to kick in but it has less effect on the sound and removes the FM hiss a bit more accurately (or actually, the Reduction strength of estimated FM hiss level setting can be reduced a bit).

  • Rough/smooth: Median position in ordered history histogram
    Controls how to combine the measurements in History size (Response speed).

    The histogram of measured noise levels over History size (Response speed) is ordered, and then the value at this position is used as the noise level.

    If the FM stereo hiss is very constant, use a low value. This reduces incorrect FM stereo hiss detection. If for some reason the stereo hiss is not constant and changes rapidly, you might need a higher value.

    Set this value as low as possible until you notice that it starts to miss hiss.
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