Another important issue has to do with localization -- the ability to discriminate which direction a sound is coming from. The microphone can't detect this at all, while the ear does in several interactive and highly complex ways. As sound enters the outer ear, tiny reflections of the sound bouncing off the pinna (the flap of skin surrounding the ear canal) recombine with the direct signal to create very complex and distinctive interference patterns (comb filtering in the range between 5 and 15 KHz.). Each different angle of arrival of a sound yields its own distinctive and audible pattern, and the brain uses these (actually it happens at the basilar membrane and in the auditory nerve on the way to the brain) to determine which direction any sound element is coming from, from each individual ear.

Also, as you probably know, the differences in sound amplitude and time between the two ears are also used to help localize the sound in space. Sound from any given point in space will have a slightly different time of arrival, spectrum and amplitude at each ear, and these differences are integrated, in the same way that our binocular vision gives us depth perceptions, into a spatial image in which the sound source is localized at some distance and direction away from us.

On the other hand, the microphone can only detect an amalgam of all the sounds arriving from all different directions. Some directional microphone designs (like cardioid and bi-directional) in effect turn down the volume of some sounds coming from some directions, but they have no way to actually discriminate the direction of the arrival of a given sound: from the left, or up, or in back, etc., while a single ear is able to localize the angle of arrival of a sound. If you don't believe this, cover one ear up and try to localize sound sources with the other. You'll find it's no particular problem, although not quite as easy or comprehensive as with both ears. The most important issue about all this is that this localization ability allows us to differentiate sounds we want to hear from background noise, which is something a microphone simply cannot do. This turns out to be a major source of difficulty when recording in a reverberant space. We can sort out the difference between the sound we wish to hear and the ambience -- the microphone cannot, so reverberant recordings tend to sound blurry.