An experiment done by Sennheiser (I think) in around 1985 showed that variations in the shape of individual pinnae make large differences to the sound arriving at the ear drum. The test was done with the company's miniature in-the-ear microphones - they looked like stethoscopes with very slim ends; much smaller than the ear canal. The sensing elements were small enough to sample the sound at the eardrum without being so large as to have much of an effect on the sound.
Each of a number of engineers listened to a musical performance while it was being recorded from their ears, in pairs of tracks on a multitrack recorder; 24 tracks enabling the simultaneous recording of 12 engineers' pairs of ears.
In playback, through in-the-ear 'phones (essential, since over-the-ear phones introduce a second set of pinnae - the listener's), each engineer was easily and unequivocally able to pick the recording that had been made through his ears, due to the large variation introduced by the various shapes of pinnae and ear canals.
This led me to suggest to a recording engineer back in 1987 a binaural microphone arrangement that produced the interaural time delay and the loudness attenuation and frequency contouring effects of the head, but eliminated the pinnae, so the listener would be free to use over-the-ear headphones for playback and hear the pinnae contribution only of his own ears. He was excited about the idea and asked if I minded if he brought it up at the next AES meeting. I said no, go ahead, and in three years Schoeps came out with their sphere microphone - which was exactly what I had envisaged:
http://www.schoeps.de/en/products/kfm6 I'm pretty sure it was just a coincidence, though. I bought one in 1995 ($8500!) and used it for about ten years, in parallel with my Royer SF12 as the main stereo "pair", but it was almost never chosen over the Royer by the client when they heard it in playback, so I sold it. I have to say, the binaural effect was not very convincing, either, so I guess I was wrong - better to have the pinnae, even if they are not your own, and use in-the-ear headphones for playback.
As an aside, there is a track on Michael Jackson's Thriller on which Bruce Swedien (the engineer) recorded the drum set with a Neumann dummy head ("Kuntzkopf"), so I guess if you listen with headphones, the drums jump out at you. I think Bruce did it just for fun, but of course almost nobody noticed.
Here's a neat DIY binaural mic project for you ardent amateurs:
http://digdagga.com/dummy/earCanals.html
