noise injection is a pretty simple device intended for use with subs (but can be used with anything).
Specifically, it adds noise (and/or a specified external input signal) onto the portion of the input signal that falls above or below a specified gain threshold. It's pretty okay at creating that nice crispy noisy sub sound.
Above level and below level control the levels of the noise/sidechain for the signals that falls above and below the threshold, respectively. Smoothing controls how smooth the transition accross the threshold is. Mode interpolates between a subtractive mode (0) where noise is subtracted from the input signal, and a multiplicative mode (1) where noise is multiplied by the input signal. Crazy mode activates crazy mode.

If you have any questions, lmk and i'll help you out to the best ot my ability. Keep in mind this thing is free and was made in a day, so it's probably got a whole lot of issues (such as working poorly with atency sometimes), and lacks a lot of features that people probably want. If you've got any requests i'll add it to the list of things to include in a possible v2.