Humans (and most animals) have two ears and this is the first key to understand how we identify where sound is coming from.
Depending on the location of sound source, the sound loudness differs between the two ears. There is also the time difference of the sound reaching each ear.
These two cues are essential for sound localization in the horizontal plane.
Depending on the location of sound source, the sound loudness differs between the two ears. There is also the time difference of the sound reaching each ear.
These two cues are essential for sound localization in the horizontal plane.
But what happens when a sound comes from anywhere along the mid-line of your head?
The sound source could be directly in the front of you, behind you, or above you. In any of these cases, there would be no difference in intensity and timing.
When you identify where the sound is coming from in the vertical plane, your brain works harder. The unique size and shape of your head and pinna (external ear) cause the different frequency profile of sound: certain frequencies get enhanced, while others get attenuated. Your brain is tuned over the course of your entire life and defines your own Head-Related Transfer Function (HRTF) to determine the location of a sound.
