Audio signal subtraction

butterman's icon

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! :)