Stereo sound is something most people are familiar with. Back in the 60s and 70s, you could buy albums that contained nothing but stereophonic sound effects. You hear a car coming from the left, then going to the right. Then, there was an airplane coming from the right flying to the left. Next to that, there is the Doppler effect. The Doppler effect is the way sound changes as it moves toward or away from the listener. There is a shift in the frequency that we, as people, can use to identify whether something is moving toward us or away from us. Think of the sound of a train passing by; if it is coming toward us, the sound will be slightly higher in tone than when it is moving away from us. Together with varying in volume, we could use this to simulate the placement of sounds in music and computer programs.

Although, at that time we, were quite impressed with this, it always turned out to be something moving from one side to the other. In HoloLens...