infinite riser filter/ shepard tone filter patch
  • Hello

    Does anyone know of an existing audulus patch that is capable of applying a shepard tone/ infinitely rising jet engine filter effect to an incoming audio signal? I am attempting to find a way to have an effect like this that runs on iPhone. I know izotope makes an AU/VST plugin that produces exactly the effect I am after but unfortunately it will not run iOS.

    https://www.izotope.com/en/products/create-and-design/mobius-filter.html

    Also here is a thread detailing the architecture of what would go into making something like this in the max/msp environment. https://cycling74.com/forums/topic/infinitely-rising-jet-engine-filter-shepard-tone-filtershepard-tone-processing/#.V-MsLWUw1Ec


    If anyone has any tips/suggestions how to achieve this using audulus, an existing patch, or a completely different app I'd infinitely appreciate any ideas you feel like sharing

    thanks so much
  • Others will probably have better ideas, but I know this has something to do with phase relationships, like you need 2-4 filters at different phases to each other - i think 4 works best for a convincing one. For rising you'd have something like an LPF whose cutoff is increasing until 20khz, then snapping back down to 20hz and going up again, and each of the 4 filters would be at 90 degree phase shifts from one another - so one filter starts at 20, the other at (20,000-20)/4, the third at (20,000-20)/2, and the fourth at (20,000-20)*3/4.