I'm getting an installation together that involves two audio sources and two microphones in close proximity, the microphones being used to detect movement within the space, so I was just wondering if it was possible to subtract the audio sources from the microphone input in max? I've tried using analyzer~ to gather the frequencies but I'm not sure how to subtract the output from the input (both of which are being generated through max). Is there any object or approach I could take that would prevent this feedback? Any help would be much appreciated! :)