The fact is one ear cannot discern the direction from which a sound comes. Two ears are required to get the job done. The ability of two ears to localize sound sources in space is called binaural effect, and is the result of the use of three cues received by the ear: interaural arrival time differences, interaural intensity differences and the pinnae.
-Interaural arrival time differences refer to the path the sound takes to get to each ear. You hear a twig break to the right of you. Naturally, your right ear is going to hear that sooner than the left since the path for that sound is shorter. Your left ear does not hear the twig snap until after that sound has traveled the additional distance to that ear.
-Interaural intensity differences follow the same principle, but refers instead to the intensity or volume of the sound. Using the same twig example, your right ear has no obstruction between it and the sound. It is a clear path. Your left ear, on the other hand, hears a lesser sound level that was created by the acoustic shadow of your head.
-The pinnae utilize two ridges in your outer ear to help the brain determine the exact direction which the sound came from. The timing between the sound hitting the first ridge and the second, clarifies exactly where the sound is coming from.
These three cues, integrated together, tell you where sound is coming from.
Why does this matter to you, the recording artist? Understanding these basic concepts about how the ear works can make the difference between a successful, money-making album and a bomb. We all want to produce the best product possible. Choosing a professional studio with an audio engineer who understands and works with these sound concepts will make your recording the best it can possibly be.
Later we will talk about how you do this in a studio.