Sometimes I get excited about silly things. In this case, I experience the real-life manifestation of a mathematical concept.
Phase The concept of phase is often a tricky one to get, since it’s a relative property: a sinusoid can only have phase relative to some reference point. The easiest way to get the concept of phase to to imagine two sinusoidal waves of the same frequency. If they are in phase, they will be exactly the same wave. These two waves will re-enforce each other, creating a wave of the same frequency with twice the amplitude. As they begin to drift out of phase, you will see two similar sinusoids drifting apart, on a plot of the two waves over time. When they become perfectly out of phase (which happens when they are 180 degrees out of phase) then the peaks of one wave correspond to the troughs of the other wave. If you add these two waves together, you get a flat 0-sized wave! They’ve cancelled each other out!
I experienced this phase cancellation phenomenom a few years ago in a record store. The speakers in the store were mounted on the wall so that you could stand at a midpoint exactly between the two speakers. At this point, the peaks of waves from one speaker corresponded with the troughs of the waves from the other speaker, and you heard almost no sound at all! It was a rather spooky phenomenom!
Incidentally, this concept of phase cancellation is important when connecting speakers to a stereo. You will notice, when wiring stereo speakers, that there ar two different colored wires. It’s usually no important (for basic magnetic coil speakers) which color wire is connected to which terminal of your stereo. What is important is making sure that you are consisted with your color choices between the two speakers. If the wires on one speaker are reversed from the other, then the waves coming from that speaker will be 180 degrees out of phase with the first, which will significantly dampen the sound coming from your stereo, since many of the waves will immediately cancel each other out! Of course, you will still here some sound, due to reflections of sound, and slight delays in sound production.