Binaural or "Synthetic Head" Stereo (Kunstkopfstereofonie)
description of binaural stereo (immediately below)	links to other sites that offer binaural sounds	brief sample binaural sounds	binaural recording at Portland State University
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Description of Binaural Stereo
Binaural stereo achieves a striking "3-D" sound ambience by recording with microphones inserted at the ear-drum locations of a dummy head which is constructed to mimic the acoustic behavior of a human head (see photos at leaft and in accompanying picture gallery). It is also possible to achieve the effect by placing miniature microphones as near as possible to the eardrums of a human head. The listener then replays the recording through headphones, whose speakers reissue the sound near the eardrum location. Thus the listener, hearing the performance later, occupies the sonic location of the acoustic dummy during the original performance. Unlike conventional stereo, which conveys primarily the distinction between left and right, binaural stereo can also reproduce vivid information about distance from the listener - and also, to a certain extent, impressions about location up and down and even front or back. The inclusion of German terminology here has to do not only with the specific topic of a German literary text, but also with the prominence of German engineering and broadcasting in the investigation and exploitation of binaural sound. That prominence, in turn, rests partially on the persistence of audio broadcasting and of the literarily respectable radio play in German culture - in part a sad consequence of WWII, which delayed the deployment of television and also created for the audio medium a sizable population of blind veterans and citizen casualties, a group large enough to sponsor its own annual prize for radio drama.

Binaural recording at Portland State University mouse pictures to see full-size (3-4x) version
go to top of this page go to "Papa Joe" home page & TOC	Binaural recording uses a "dummy" or reproduction of a human head (Kunstkopf = artificial head). Ideally the artificial head should mimic the substances of an actual head, so that it will behave acoustically the same. For its professional productions Bavarian Broadcasting used a dummy originally intended for binaural. At PSU we used "Kemar," borrowed from the Department of Speech Communication. Ordinarily Kemar is used by the Speech and Hearing Sciences program to calibrate hearing aids. The dummy is designed to be an androgynous close approximation of the human physical average.
	The back of Kemar's head can be removed to attach equipment to the simulated ear areas. Here Radio Shack miniature microphones have been inserted from within the head into the ear holes and secured with modeling clay. Leads from the microphones, held in place with friction tape, pass through the hollow torso to the recorder. Kemar's head is hollow and thus does not resemble those of most human beings. To simulate the physical presence of a brain we stuffed the cavity with a sack of Blue Ice.
go to top of this page go to "Papa Joe" home page & TOC	Miniature microphone in Kemar's ear hole. The effects of the external ear (pinna or auricle) on the sense of location and distance of sounds are crucial for ordinary hearing and thus for binaural recording. Kemar comes equipped with detachable external ears that fasten to the posts around the earholes. The miniature microphones fit tightly through the holes in the rubber pinnae. Although one would think the mikes should be recessed as far as possible, as though in ear canals, they worked better when they protruded about 1/8" (2-3mm).
go to top of this page go to "Papa Joe" home page & TOC	Kemar being fitted out for a recording trip by a participant in the German Radio Drama (Hörspiel) course. The dummy does not have an openable mouth, much less a simulated vocal tract. Also, the chest cavity is hollow. We suspect the lack of such features did not much affect the fidelity of the externally-produced sounds recorded through Kemar. But in our production of "Papa Joe & Co" we wanted Kemar's acoustical perspective, and thus his physical position, to be identical with that of one of the characters. We considered playing the character's pre-recorded speeches back through a small loudspeaker just in front of Kemar's mouth, but the lack of an imitation vocal track and internal head mass suggested it would be ineffective.
	Since Kemar was to be not just a passive observer/auditor of the action around him, he and our recording equipment needed to be mobile. Binaural recording does not strongly reproduce the vertical dimension, but in order not to undermine whatever effect there might be, and to make performance easier for our actors, we placed the dummy on a cart that established Kemar's height at about 5'8" (170cm). During our several recording ventures through the buildings of the university and nearby parks and streets we found Kemar to be an excellent attention-getter and conversation-starter. We much regretted not having had him around in our socially awkward youth.
go to top of this page go to "Papa Joe" home page & TOC	The recording experiments we did before staging "Papa Joe & Co." were very useful. Although we were not expert sound technicians, we had to unlearn some of the ideas we had absorbed that are quite legitimate for conventional recording, but not for binaural. Perhaps most important was that, unless one has a studio richly set up for binaural, conditions for recording should not be "clean." Conventional recording may value the presence of ambience, but binaural needs almost "dirty" surroundings. Since one is striving to retain the dimensions and directions of the performance space, and can do so solely by acoustical means, it is important to give the listeners a steady supply of "clues" that remind them, almost subconsciously, of its existence.
go to top of this page go to "Papa Joe" home page & TOC	On our binaural "field trips" we encountered several musicians. Certainly the binaural effect can enhance one's experience of music, but our fundamental intent to make the binaural "synthetic head" a surrogate participant in dramatic action caused us to feel that static recording of conventional performances did not fully exploit the effect. One wonders how it would work in performances that integrate audience participation. Technical note: We did trial recordings with an analog cassette recorder, as shown here, but then switched to DAT. We lack the expertise to say how the binaural effect is affected by analog copy-generation deterioration or, in the digital domain, by differences in sampling rates and bit-depth.
	Kemar dummy set up for recording at home. The hat and jacket were added initially as whims; later their use was legitimized by PSU audiology faculty who explained that such props make the acoustic ambience more lifelike and are customarily used when the dummy is used for calibration of hearing aids.
	Living room where two of the sample sounds available above were recorded. The room is actually two rooms connected by a broad archway, where the dummy stands in the photo here. This photo shows the larger of the two rooms. For the "water" sound the dummy was placed on the near part of the Oriental rug, facing the couch at the far wall. For the "fire" sound it was rolled into the smaller room, whose floor can be seen at bottom left, and placed so that the fireplace was about six feet from its back left.