Mr. Schulein described a personal, portable system that allows for simultaneous binaural recording and monitoring. Miniature electret microphones are attached to insert earphones, so that the microphones are located at the ear canal entry. Careful consideration was made of the difference between the sound field sensed at the outside of a blocked ear canal versus that at the eardrum when the canal is open, and it was shown that the frequency response of this transfer function is quite independent of sound field direction. Such corrective equalization was implemented acoustically by virtue of the coupler frequency response of the earphones selected.
Live and pre-recorded demonstrations were conducted to
evaluate the technique and to show how visual and other non-auditory cues
affect directional sound perception. The binaural signal was broadcast with a
wireless transmitter, and each audience member was given a receiver and
insert earphones. For the live examples, a volunteer was fitted with the
system described above. First, Mr. Schulein spoke
while walking around the room, and the audience was able to hear the sound as
if he or she was sitting in the location of the volunteer. Next was a
pre-recorded voice sample coming from a sequence of locations in the
horizontal plane around the head, played first with the audience stationary
and then with the audience physically rotating so that the virtual source
remained stationary. This was followed by binaural
audio/video recordings made by Mr. Schulein in
The live demonstrations generated enthusiastic discussion, and were special in that each audience member was able to experience binaural reproduction first-hand.