What I meant by ’different threshold values’ was that each of the resulting three levels carries a different amount of noise.
The Transient layer has the least amount, if any.
The Tonal has some noise.
The Noise layer obviously has the most, where some of the noise actually is ’wanted noise’; e.g. the ’tails’ after each drop, and other ambience carrying information.
Hence the threshold values for the respektive layers must be set differently in the Unmixing levels dialogue box.
With a boosted audio file you could always use your ears to set the best value, but with this levelwise weak and quiet audio at hand it’s harder.
Like you show with your last screendump the mouse position shows only two of the dimensions of the spectrogram; time and frequency.
It would perhaps be of some help if it also showed the third aspect, the amplitude. If nothing else but for the sake of completeness.
The parameters for the Threshold value is set automatically after having done the Analysis in the dialogue box (Unmix levels). Unfortunately that value is not of much use since it will mostly be too high. You often, if not always, have to change to a much lower negative value for things to happen.
Maybe it’s easier to see and address the noise if you use the 3D-tilting of the spectrogram, the ’wanted’ areas would perhaps stand out a little more from the background/noise.
And using a colour scheme like Magma or inferno, where stronger amplitudes are whiteish.
Speaking of feathering selections, there is a new feathering (and also an unfeathering) tool among the tools to the left. It looks like a little sun, with a dashed circumscription. You can use that by clicking on the borders of a selection to make it more feathery.
Otherwise you can fade a selection - before using it - by setting the fade value in the information line to the left above the spectrogram. Applied on the Frequency range selection there will be fades on both the upper and lower border, but pushing the whole selection down towards the zero Hz the lower fade will finally disappear.