Win10/Audacity 3.1.3

Right now this is, for me, an academic question, but it might apply to any two-step Effect on audio tracks.

I am applying Noise Reduction to a 50-minute audio recording; I select a chunk of “noise only” and prime the Effect, Noise Reduction; then I Select All and apply Noise Reduction. This is the regular two-step application of the effect “Noise Reduction”.

**Question 1:** Since I have primed Noise Reduction from the file, it follows that at least *that* part of the track must change. Therefore the track that results from Noise Reduction on a track must, by definition, always produce a change in that track, a change that would be picked up by any binary-compare program. Am I correct?

**Question 2:** The time to process will always be a function of:-

(a) The number of matches of the Noise Profile within the track and hence -

(b) The length of the track, and possibly -

(c) The length of the selection offered up as a Noise Profile

This third parameter is the one of most interest to me. I reason that the shorter the Noise Profile, the greater the chance of a match being made, which would impact (a). Are (a), (b) and (c) correct?

**Question 3:** (and this is a scarier question IMHO) If the Noise Profile remains in place for successive processing on a series of files, then the binary-compare program could deliver a datum for each file showing what percentage (I am not specifying the units - number of areas of changes, count of bits of change etc) of each track was changed due to the Noise Profile of the first track, and hence one could calculate the probability of improvement in repeated applications of the Noise Profile on a series of tracks recorded in the same venue on the same day over a single period. Is this correct?

Thanks, Chris