Comb Filtering

Comb filtering can exist whenever you have multiple signal sources (i.e. loudspeakers) or microphones in proximity to each other.  For example, if you have two microphones recording the same signal, it can sound way worse than a single microphone, and this is because the signal mix together and create destructive interference.  

A comb filter is also created if a loudspeaker or microphone is placed in close proximity to a wall -- the wall essentially acts as a mirror, and creates a virtual sound source in the mirror position.

There are many places on the internet you can find information on comb filtering, so I'm not going to get deeply into describing it.  Rather, give you a demo you can use to interactively look at how comb filtering works by moving a microphone around a pair of speakers.  You can adjust the location of the microphone and the speaker-speaker spacing.   This is a simplistic model that assumes everything is omni-directional, but it does give a good sense of how comb filters work.  Just click  the image on the right and go ahead and play around with the tool.  This doesn't work well from a phone.  Better head to your computer.

This example is written in python, and hosted on GitHub here.  You should be able to access it directly using Binder.