I'm trying to develop an effect algorithm and I don't know what to call it. I want it to reduce high frequency noises that have an amplitude above a given threshold, but if high frequencies have an amplitude below that threshold, they should pass through the filter untouched (well, maybe untouched... a phase shift would be acceptable). Is there a good name for this effect? It's not EQ or LPF, both of which cause a gain effect to everything in the frequency band regardless of the input amplitude.
I want my effect to tame harsh high frequency noise without dulling high harmonics. The closest thing I've found in open source effects is Airwindows Accel/Accel2. Those names are short for "acceleration limiter", but I don't think that really describes the effect. I looked at the mathematics in those plugins, and they're not what differential calculus would define as a limit on the acceleration.
Any suggestions?