Journal of the Society of Motion Picture Engineers (1930-1949)
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on the speakers one at a time and then play back the recorded material a second time to get the second speaker. In some recently conducted tests it was found that if two conversations are simultaneously recorded, a capable operator can produce an accurate transcription even when the desired conversation was recorded at a 13-db lower level than the unwanted dialogue.
In radio and motion picture work the second recording channel may be used as a cue or control track for special effects or for recording commentary along with the primary intelligence.
In the laboratory or for field-test work the binaural equipment may be used for recording either binaural or dual-track test data for later careful analysis. Figure 3 shows a binaural recorder in field use by a prominent automobile manufacturer. Note that this setup shows the predecessor to the dual-channel amplifier unit.
The field of audio-visual education utilizes realism as a teaching aid. This portable binaural packaged system readily lends its "third-dimensional" sound reality to assist in critical analysis of band or choir practice, speech classes, dramatics, etc.
Conclusion
1 . No appreciable sacrifice in quality from that of a standard ^-in. tape recording system was necessary in these units.
2. The resultant equipment as manufactured is really of a portable nature and is housed in two carrying cases. The amplifier unit weighs but 37 Ib, while the tape transport has a weight of 29 Ib.
3. From the foregoing data, it is apparent that the design objectives of producing a practical but low-cost commercial binaural record-reproduce magnetic tape equipment were accomplished.
References and Bibliography
1. Stereophonic Sound-Film System, a symposium of seven papers presented May 1941 at the Spring Meeting of the SMPE at Rochester, N.Y. Published as Bell Telephone System Monograph B-1327, 1941; and in Jour. SMPE, 37: 331-426, Oct. 1941; consisting of: H. Fletcher, "General Theory";
E. G. Wente, R. Biddulph, L. A. Elmer and A. B. Anderson, "Mechanical and optical equipment for the stereophonic sound-film system";
J. G. Steinberg, "Pre and post-equalization of compandor systems";
W. B. Snow and A. R. Soffel, "Electrical equipment for the stereophonic soundfilm system";
E. G. Wente and R. Biddulph, "Lightvalve for the stereophonic sound-film system" ;
E. G. Wente and A. H. M{Uler, "Internally damped rollers";
L. A. Elmer, "A non-cinching film rewind machine." Note: The first three of the above
papers were published also in /. Acoust.
Soc. Am., 13: 89-114, Oct. 1941.
2. H. Fletcher, "Auditory patterns," Revs. Modern Phys., 12: 47-65, Jan. 1940.
3. Wire Transmission of Symphonic Music and Its Reproduction in Auditory Perspective, a symposium of six papers presented at the Winter Convention of AIEE, Jan. 1934. Published as Bell Telephone System Monograph B-784, 1934; in Elec. Eng., 53: 9-32, 216-218, Jan. 1934; and Bell System Tech. /., 13: 239-310, Apr. 1934; consisting of: H. Fletcher, "Basic requirements";
J. C. Steinberg and W. B. Snow, "Physical factors";
E. G. Wente and A. L. Thuras, "Loudspeakers and microphones" ;
E. O. Scriven, "Amplifiers";
H. A. Affel, R. W. Chesnut and R. H. Mills, "Transmission line";
E. H. Bedell and Iden Kerney, "Systei adaptation."
4. Lorin D. Grignon, "Experiment stereophonic sound," Jour. SMPE, 280-292, Mar. 1949.
5. J. P. Maxfield, A. W. Golledge and T. Friebus, "Pick-up for sound moti( pictures (including stereophonic)," Jo SMPE, 30: 666-679, June 1938.
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August 1952 Journal of the SMPTE Vol. 59