PS AUDIO:
It is not difficult to imagine left, right, and center imaging on a stereo system.
It's also likely not too much of a stretch to understand depth. After all, a proper stereo recording reproduces depth as a measure of how far away from the recording microphones the instruments or performers are.
Harder for most people to grasp is imaging height. How is it that the left and right speakers can provide an illusion of height?
When we're recording a singer at Octave Records, they are typically facing directly at the microphone and in fairly close proximity. Being that close, how then on a good recording can we hear if the singer is seated or standing?
Typically, this is a result of how boundaries change sound. When you are seated the microphone (and you) are closer to the floor. Standing up is the opposite.
How does being closer to the floor sound? It's easy to try a little experiment to find out. In a quiet room, start speaking in the middle of the room. Listen carefully to the quality of your voice. As you continue speaking and listening, move closer to a boundary wall. Note how your voice changes: a reinforcement of upper and lower tones will likely be evident.
It might be subtle but in a properly setup system and on a good recording it's easy to hear height as well as depth.