noise.js | ambient sound synthesis library | Audio Utils library

Here is my canvas on jsfiddle:

https://jsfiddle.net/vzrandom/fkho6grf/8/

I'm using simplex-noise.js and dat.GUI to create movement of particles. There is simulated click on canvas every 5 seconds. On click first animation is coming in background and new animation starts.

My problem is that animation on click starts too abruptly. I would like to have some kind of fade in of particles.

It seems like a simple problem but somehow I can't get it how to make fade in of elements that are inside the canvas - not entire canvas himself.

Entire code is on jsfiddle, here is part that handles the click: