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Binaural Basics.Pdf INAURAL Binaural recordings will add a new dimension to your audio world. JOHN SUNlER mikes feed two channels which are kept entirely separated from the source all the way to the final listener, whether live, a record- ing, or a broadcast. The listener wears stereo headphones and the between the two. That's because original left ear signal must be most source material isn't de- routed properly to the left ear and ALTHOUGH MOST AUDIOPHJLES ARE signed for headphone listening. the right to the right or the effect familiar with the term binal~ral, An unnaturally exaggerated is compromised. The final result there's still quite a bit of con- effect is created with head- is for the listener to be sonically fusion about it. Early in stereo phones, as though half an or- transported to where the sounds history the terms binaural and chestra is on one side of your originated, rather than attempt- stereo were used interchangea- head and the other half on the ing to bring the sounds into the bly, even though the two record- other side, with a hole in the mid- listener's room as with speakers. ing methods are totally different. dle. Also, the music sounds as if The left speaker signal is pre- Recording pioneer Emory Cook it's happening inside your head vented from feeding into the lis- caused some of that confusion by rather than out in the room. No tener's right ear, and vice versa, calling his early 50's twin- serious record producer would with binaural playback on stereo grooved stereo LP's binaural ever monitor a recording session headphones. Figure 1-a-d shows when they were actually stereo. solely on headphones; a proper various types of sound reproduc- Binaural recordings can open setup of the highest quality tions, including binaural. up a whole new realm to your 11s- monitor loudspeakers is re- With binaural recording, spa- tening enjoyment. We'll look at quired to get a feeling for proper tial placement within a 360-de- the history behind binaural balance in the mix. gree sphere is so realistic that sound and how it is made as well even vertical placement is per- as present some high-quality Binaural background ceived. Reproduction of the am- binaural products. True binaural uses only two mi- bience or reflected sounds in a crophones, usually small electret hall is so correct that acoustical The binaural difference condensers either set into the engineers can listen to such 0 If you listen to a stereo source outer ears of an artificial human tapes and identify in which hall 8 from stereo headphones com- head. or at least spaced the same they were recorded. The only pared lo the same source listened distance apart as an average pair areas of location that are some- gn to from loudspeakers, you'll of ears, and mounted on either times problematic are on a line $ notice a much different sound side of a small baffle. The two directly in front of and to the rear of the listener. That is dependent on several factors, including how our hearing mechanism works, differences in headphones, and individual differences as well as learned responses. Binaural history The first use of binaural sound occurred in 1881 in Paris. Inven- tor Clement Ader mounted a se- ries of primitive carbon tele- phone transmitters along the front of the stage of the Paris Op- era House. The transmitters were grouped in pairs the same dis- tance apart as human ears, with several pairs across. The leftmost of each pair were mixed together and fed to one telephone line, which listeners in their homes directed to their left ears using the ordinary phone earpiece. The rightmost of each pair were also mixed together and fed to a sec- ond phone line, which each lis- tener had to have installed in their home. The result was that as opera singers moved about the stage, home listeners could "see" their movement while hearing the music with much greater fidelity than a single phone line could possibly provide. The origi- nal patent says "This double lis- tening to sound. .. produces the same effects on the ear that the stereoscope produces on the eye." It's fortunate that a wide fre- quency response is not the most important parameter for con- veying the binaural effect; phase accuracy and correct balance be- tween the two channels is more and stereophonic (d). important. A similar project was carried dummy head, which was hand- vironment were the voices of the out with an improved version of made for the project. Music ex- woman, speaking English, and the Ader experiment in Berlin in cerpts from it are still currently the man, greeting her in Ger- 1925. During that same year available on a pre-recorded cas- man. Eventually they meet in more than one radio station in sette. The Sennheiser micro- front of the listener. All the while the U.S. did experimental bin- phonelheadphone people in Ger- you can easily focus on either the aural broadcasts using two dif- many issued a series of 45-rpm German or the English and un- ferent frequencies. Listeners binaural demo recordings (long derstand perfectly without se- needed two crystal sets, each out of print now), which were rious distraction from the other feeding a separate earphone. The well done and designed to pro- voice, as would occur with stereo mikes in the studio were kept mote their open-air phones and sound and certainly with mono about seven inches apart, and special binaural mike system. Di- reproduction. therefore listeners with only one agrams of the placement of musi- This very functional use of bin- radio still heard a normal signal. cians and sounds around the aural is currently being applied (I)g During the last 40 years there listener aided in evaluating how to military aircraft communica- has been sporadic interest in bin- precise the effects were. 0 tion by researchers at the NASA- 2 aural reproduction around the One demo in particular was in- Ames Research Center. They use 2 world, centered primarily in Eu- teresting. It featured a woman ar- a powerful computer known as -1 rope and Japan. In 1970, Stereo riving on a train and being met the Convolvotron to process 5' Review issued a binaural demon- 0 by a man at the station. Placed mono speech and signals from o stration LP of music and sound among all the sound effects of the several sources, such as control $ effects using the "Blue Max" train, people, and station en- con tin ued on page 84 is just as likely to happen when Frankly, experience has shown that of why some records sounded so bad. monitors with droopy high-frequency there's no reason to trust the hearing But we need look back no.further response are used. Many years ago, I acuity or good judgement of those than .the hundreds of shrill-sounding remember reading about a technical responsible for the sound of our mu- CD's released when the format was survey of the speakers used in sound sical software. True, things are a lot new to realize that incompetent engi- studios and how appalling their fre- better than in the early 196OVs,when I neering is not a rare phenomena in quency performance was. first started looking into the problem the record business. R-IE towers and other aircraft, and as- sign them places in a 360-degree sphere so that pilots wearing stereo headphones can "steer" their binaural hearing to the voice they need to hear and ig- nore the rest. A demo tape mixed Seminars Eday............. mtwal those artificial binaural voices into a loud background of heli- Meeting Weekend ......... ~orksliop copter noise and contrasted the .................... Papers Daily Teclmical Papers very intelligible result with the Daily .................... Equipment Exhibits same signals in both mono and Tutorials Daily ....................Social Events stereo. Exhibits Much research is currently Who Will Attend? being done on the human hear- * Presidents, CEOs Owners a Cameramen Chief En ' eers * TV Maintenance Supenisors ing mechanism and the broad * Sales & Marketing VPs * Designers * A/" ~egcians * Grayluc Artists field known as psychoacoustics. * Consultants .Producers Systems Engineers * Tape Editors Product approaches being pro- Directors of Operatiolis Marketing Managers Teclmical Supenrisors * Video Editors Students Publishers Production Managers * Digital Effects Designers moted, such as Hughes SRS and .~ooeo..oe..o.o~.... o~~~~~oe~o~~oo~~o~eooQ Sound, are an outgrowth of 1: E hl 0 0 0 For More Information, Mail To: that work. Those systems at- Society of Motion Picture and lami Title 0 tempt to offer a binaural-like sur- 6 : Television Engineers 0 DI. Co. e round localization with loud- I- 595 W. Hartsdale Ave., speakers rather than stereo . White Plains, NY 10607 Street . (914)761-llW*hx#914-761-3115 City 0 headphones, and only a pair of Ltl PLEASE RUSH THE FOLLOWING INFORMATION: State zip Country them at that. With proper source Exhibitor Full Conference Registration ~~1, Fax 0 material, mixing, and proper $ 0 Exhibit Only Tutorial Seminar Workshop 0 continued on page 86 [email protected]... O~bO@@~OOO~~~OO~O~ 84 dard oscilloscope is the vertical cir- You can change any of the criteria cuitry. Although there are special you want but, for the moment, it's a considerations, this is really nothing good idea to leave them all as they more than an amplifier designed to are. Once we get into the specifics of have a response that's as flat as pos- the design, you'll find it relatively easy sible over the rated bandwidth of the to modify some of the features to placement of the listener in the scope.
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