[fundamental]

So, from the second figure you can see that you have a series of decaying envelopes. For the individual taps you should be able to model this as some event at an unknown scale with an apriori rate of decay. You can easily discard the non-activity regions based upon some windowed estimates of the energy. That leaves you with what's essentially a template matching type of problem for each of the three areas where the signal is showing above noise levels of activity. The first and last region don't match the decaying exponential well and the middle one matches it fairly well with 3 distinct events.

That said, this approach introduces what may be more latency, coding complexity, and computational work than is desired. I'd take a look at a spectrogram and see if there's some bandpass filter which makes it easier to see these events compared to the 'false activity'.