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Flanger Inverted Mode

A different type of maximum depth is obtained for $ g=-1$ . In this case, the peaks and notches of the $ g=1$ case trade places. In practice, the depth control $ g$ is usually constrained to the interval $ [0,1]$ , and a sign inversion for $ g$ is controlled separately using a ``phase inversion'' switch.

In inverted mode, unless the delay $ M$ is very large, the bass response will be weak, since the first notch is at dc. This case usually sounds high-pass filtered relative to the ``in-phase'' case ($ g>0$ ).

As the notch spacing grows very large ($ M$ shrinks), the amplitude response approaches that of a first-order difference $ y(n) = x(n) -
x(n-1)$ , which approximates a differentiator $ y(t) =
\frac{d}{dt}x(t)$ . An ideal differentiator eliminates dc and provides a progressive high-frequency boost rising 6 dB per octave (specifically, the amplitude response is $ \left\vert H(\omega)\right\vert =
\left\vert\omega\right\vert$ ).

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``Physical Audio Signal Processing'', by Julius O. Smith III, W3K Publishing, 2010, ISBN 978-0-9745607-2-4.
Copyright © 2017-02-20 by Julius O. Smith III
Center for Computer Research in Music and Acoustics (CCRMA),   Stanford University