Consider a sound that originates precisely five feet directly above your head. Now consider that very same?

Question

4. Consider a sound that originates precisely five feet directly above your head. Now consider that very same sound, but originating precisely five feet below your head. Given your knowledge of hearing physiology, are easily able to distinguish the origins of each of these sounds? Why or why not? For help, consider a scenario where the sounds instead originated from your left and right at the same distance.

Answer 1

You cannot distinguish the origins of the sounds because they are equal distance above and below, as in the example of left and right.  The same principle as a stereo system set flat and you sitting directly between the two speakers.  It sounds like one sound, not two separate sounds.

Answer 2

I'm afraid the above answerer is wrong.

You may have wondered why the pinnae (the visible parts of the two ears) are shaped in such a strange manner.  The answer is that their odd shape changes the quality of the sound entering the ear, depending on the direction from which the sound comes.  It does this by emphasizing specific sound frequencies from the different directions.  The brain uses these changed frequencies to infer whether the sound comes from in front or behind, or from above or below.

To tell whether the sound comes from the left or the right, the brain has two other tricks it uses.

  

(1) Firstly, it uses the lag time between the entry of sound into one ear and into the opposite ear.  For instance, a sound coming from your right will enter the right ear just before it enters the left.

(2) Secondly, it uses the difference in the intensities of the sounds in the two ears.  A sound coming from your right will sound slightly louder to your right ear than to your left.

So to sum up, the brain uses the above 2 mechanisms to tell whether a sound is coming from the left or the right.  It uses the pinnae to tell if the sound is coming from above/below or in front/behind.