In the field of
Physics, Destructive Interference usually refers to the
Interference of waves. Destructive Interference basically refers to the tendency of two
opposite waves cancelling each other out. Sound waves are a good example, and you can see Destructive Interference in action if you have a
tuning fork around.
Basically, when you
whack the fork, the noise coming off the flat faces of the two
prongs is much louder then the noise coming from the corners of them.
I'm not entirely sure how this works, because I came really close to failing
physics. But I've seen (or rather heard) it.
This is actually being used (well,
prototyped right now) in really new
cars - basically, you have large
speakers under the
seats, and then
microphones pick up noise coming into the car. The speakers then generate the
opposite sound wave, and the two cancel each other out for a totally
silent trip.
The only other thing I recall is that my
teacher said it should be possible for
airplanes to
mask themselves from
radar with destructive interference like this. Radar as mostly based on
echoing sound
waves, so if the plane had a radar detector that identified the
frequency the radar was using, it could generate the opposite wave and cancel the radar beam out as it comes towards it. I guess the receiver would still get a
blip for a second, but it would at least
distort it after that.