moving custom function applied to acoustics

[Hella]

Reference Issues/PRs

What does this implement/fix? Explain your changes.

This pull request implements the Crest Factor Detrending and Sorted Density. There are two versions available - causal and anticausal. It works together with https://github.com/Hella/l2f .

Any other comments?

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✅ Hella
❌ Helena Peic Tukuljac

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