Audiofilter

[jonathanpostawka]

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[TimZiemer]

Please fill out the issue description. By the way: In ziemersteaching branch you can find my example of an all pass filer in shorttimefouriertransform.ipynb. It works, but I defined a static phase manipulation ((ϕ^5)/7 or so), instead of a variable (ϕ^f(t) or alike).