In making anti sound work the offending sources need to be detected such as a fine dust picks up fingerprints on a smooth surface.  That information would then be sent back at the speed of light to the dsp for synthesis.  To account for echo delays, a modification of source placement and detection has to be contrived, along with reasonable estimates of layout travel time calculation.  Ideal environments for detection and consequent dampening would be plasma, where the gas itself is 3-dimensionally able to act as the counter propagator.  Human ears don’t last long enough to hear in a plasma induced by thermal motion.

 With regard to detection, the vibrating window of spy methodologies come as a crude centerpiece.  That of course is great for simple detection in a classic setting, but fails entirely in any other local.  A momentary gas dipole under the influence of a radiation field could act as an inductor if a local detection device was planted.