Folks, (Sorry for the cross-posting.) I'm looking for someone who knows how to write DirectXplug-ins and who is willing to devote a small amount of time to help advance scientific knowledge. The goal is to settle for once and for all whether phase shift alone is audible, and whether having a frequency response beyond the 20 Hz. to 20 KHz. boundaries is really audible. One plug-in I'm looking for will implement an all-pass filter in DSP, and allow varying the amount of phase shift / corner frequency with a slider. This is essentially how a phaser (not flanger) stomp box works, but without the part that sums the input and output to create the dips and peaks. The other plug-in will have two sliders to control at what frequencies the upper and lower extremes are rolled off. The slopes need to be sharp (or better, adjustable), and the sliders must of course be calibrated. Further, this plug-in needs to work at a 96 KHz. sample rate so the test audio source (pink noise, whatever) can have frequencies higher than 20 KHz. yet avoid the additional sharp filtering inherent in a 44.1 KHz. sample rate. Both of theseplug-inswill then be distributed freely so everyone can try these experiments. Any takers? If you are willing to help me with this experiment, please go to my web site at http://www.ethanwiner.com and click the "email Ethan" button near the top of the screen. Thanks! --Ethan Winer http://www.ethanwiner.com/articles.html "The truth is in there"