BINAURAL FOR BEGINNERS (FAQs)

CONTENTS:

1. So Just What IS Binaural?
2. Sounds like a record industry marketing ploy...
3. How are binaural recordings made?
4. What the heck are HRTFs?
5. Does it matter if the two channels get mixed up?
6. How do you listen to binaural recordings?
7. Are they useless on loudspeakers?
8. Is there anything different about binaural on stereo speakers?
9. Why doesn't stereo on speakers approach the realism of binaural on headphones?
10. What else besides headphones is needed?
11. What headphones do you recommend?
12. Can I plug my phones directly into my computer?
13. How can I sample these special recordings?
14. Is there a source for binaural recordings?
15. Why are some of these CDs so expensive?

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So Just What IS Binaural?

The above double photo is probably familiar to most persons - it's an old-fashioned 3D stereograph. It was photographed with two lenses about 2 1/2 inches apart, duplicating the separation of our eyes. When the two photos of slightly different perspective are seen in a stereoscope viewer that shows only the left image to the left eye and the right image to the right eye, the brain assembles them into a virtual image with a natural third dimension.

Binaural carries out a roughly similar operation, recording music and sounds with two tiny omnidirectional mikes at the entrance to the ear canals on an artificial head replicating human features (with the ears about 6 to 8 inches apart). This includes even the fleshy ridges of the outer ears which modify the frequency balance of sounds depending on the direction from which they originate. The two channels of sound are kept totally separate from the original recording site to the two drivers on the headphones worn by the listener. Since only two channels are required, binaural is compatible with stereo. Just as the left eye must view the left image of the stereopticon, it is important that the signal from the left ear mike on the dummy head goes to the left ear of the listener and vice versa. There is no mixing of the two channels as with stereo loudspeaker playback (and often recording too). By the way, binaural is almost as old-fashioned as the stereopticon - the first experiments took place in 1881 on the stage of the Paris Opera using double telephone lines to subscribers!

It is important to recognize the difference between a stereophonic system and a binaural system. The former system uses loudspeakers but requires an infinite number of channels for perfect reproduction. The latter requires only two channels for perfect reproduction but involves the use of a pair of head receivers [drivers] held tightly to the ears for each listener. All listeners with such a system can be given the illusion of sitting in the best seat in the concert hall.  ...Harvey Fletcher in the SMPTE Journal Vol. 61, September 1953.

The binaural experience is striking, and requires no special equipment besides stereo headphones and binaural recordings. While binaural doesn't depend on the highest fidelity to achieve its amazing realism, the better the playback equipment and headphones, the better will be the sound. On the other hand, the simplest ear-buds and a portable CD player can provide plenty of binaural thrills! The listener is placed exactly where the performance or sound originated, with sounds localized in a 360-degree sphere around one. The live ambience of the hall in which a musical performance takes place is preserved more precisely than with an expensive multi-speaker surround sound system.

All modern binaural recordings are compatible for loudspeaker playback, but unless you turn the speakers in and sit between them, you will lose most of the pin-point localization. However, when played through a matrix surround decoder and multi-loudspeakers, most binaural recordings will be found to provide a more natural surround soundfield than specially-encoded music surround CDs. This is due to the very clean phase (L-R) information that they preserve between their two discrete channels.

Uh huh. Sounds to me like another new record industry marketing ploy, such as New Orthopedic Sound or 34D Stereo...

Not so. In fact Binaural is really much older than stereo and even follows the phonograph by only four years! It was first used in transmission of opera from the stage of the Paris Opera House in 1881. Inventor Clement Ader used pairs of carbon telephone transmitters across the stage, mixed down to two separate telephone lines going to the homes of subscribers. They had to have two telephones and put the receivers from each one to their ears. Hyper-binaural ear trumpets were used by the Air Force in the First World War to aid in locating enemy planes. In the 1920's there were experimental binaural radio broadcasts using a pair of frequencies, with listeners tuning in on a pair of crystal sets. At the 1939 World's Fair, the binaural dummy head "Oscar" was a major attraction, with people lining up to don headphones and experience what was happening in the room in which Oscar was placed.

How are binaural recordings made now?

[Click on photo for larger image]

Most binaural recording today is done with an artificial or "dummy" head replicating the human head not only in average dimensions and details but also in approximate hardness and softness of skin and bone. One researcher even worked for a time with actual human skulls, but eventually found synthetic materials to be easier to use. Some of the recording heads also model the shoulders and many have hair on the head, because all of these details have an effect on the sound picked up by the two mikes. These mikes are usually tiny omnidirectional condensers mounted at or near the entrance to the ear canals. Some designs have placed the mikes at the same location as the eardrums, with special equalization to correct for the double traversal of the ear canal (first in recording and again in playback). At any rate, placement of the mikes somewhere inside the pinna or outer ears allows them to preserve the Head Related Transfer Functions or HRTFs. For more details on the Neumann KU-100 binaural head Go Here.

What the heck are HRTFs?

They provide the brain with changing spectral characteristics or frequency response depending on the direction of particular sounds. The ridges of the pinna, as well as the other features of the head and shoulders act as multiple frequency-selective band-pass filters tuned to the azimuth and elevation of every sound in our environment. The minute shifts in frequency response, phase and sound level gives the brain the data to localize the sounds. Without HRTFs our ancestors would have been all eaten up by predators and we might not be here today! You can test this phenomenon easily by snapping your fingers, first directly in front of you and then at the same distance to your right or left. Notice the entirely different timbre of the sounds -- duller when in front and with more high frequencies when to the side where the sound is directed on a straight path right into your ear canal. You can also have someone snap their fingers behind you as well as in front while your eyes are closed. This will demonstrate that localization is the least accurate for sounds on a direct line through the center of the head -- in other words equidistant from each ear. Some listeners to binaural have trouble locating the sounds exactly in front or behind, but this is also a fault of normal hearing.

Does it matter if the two channels get bolluxed up along the way?

Yes! It is vitally important to keep the two channels carrying the binaural signals completely separate, with no mixing as frequently occurs with stereo recording. The left ear signal must also be heard at the playback end by the listener's left ear and vice versa. Many binaural recordings begin with an identification of the two channels since this is even more important than with stereo recordings. Reversing the channels gives the equivalent of having had your back to the performers when they were playing; the facial features on the front of our heads are missing on the back of our heads!

How do you listen to binaural recordings or broadcasts for the full effect?

At the listening end, stereo headphones must be used, except for a couple of complex and expensive processes that allow loudspeaker listening to binaural while retaining the "you are there" 360-degree realism. An alternate, inexpensive, but rather unwieldly approach is Ambiophonics - the use of a baffle between a pair of closely-spaced loudspeakers. However, a number of manufacturers are working on improved binaural playback via crosstalk-cancelled loudspeakers.

So does that mean binaural recordings are totally useless for ordinary listening on loudspeakers?

Not at all! All modern binaural recordings can be heard via standard speakers with excellent results -- very similar to good purist-miked stereo recordings, but without the transporting binaural realism. Some audio critics feel they're even better than the best audiophile stereo recordings! (See the BINAURAL BULLETIN page for a review addressing this subject.) Early binaural recordings sometimes sounded thin and distant when heard via speakers, but special equalization built into both current professional dummy heads, made by Neumann and Aachen Head Acoustics respectively, corrects this fault.

The ultimate experience of binaural recordings via just a pair of speakers can be had with the three Lexicon digital surround processors, the CP-1, CP-3 and the latest models DC-1 and 2. All include a proprietary Binaural Panorama circuit, which among other things cancels out the left speaker sound reaching your right ear and vice versa. The result, within a narrow "sweet spot," is really the best avenue to experiencing 100% of the "you are there-ness" of binaural using speakers instead of headphones! Those who have difficulty with frontal location of sounds and/or locating the sounds outside of their head also find the Lexicon processing solution with speakers to be the most advanced way to listen to binaural recordings. For more info: http://www.lexicon.com

There is also a similar and much less expensive Simple Approach to Loudspeaker Binaural offered by Kevin Brown on his noncommercial site. It uses three identical speakers and requires the listener to sit exactly equidistant from all three. The simpler of the two needs nothing else, but the speakers must be full-range drivers without crossovers. Also produces a narrow "sweet spot," but a major advantage is the superior out-front placement of sounds vs. binaural on headphones.

A really simple way to get some of the binaural experience if you have no headphones

 

 




Is there anything really different about the sound of binaural recordings on stereo speakers?

Yes! They're great for surround sound! A special attribute of all binaural recordings is a very precise L - R or ambient component to the two-channel signal. Since this is the type of information most surround sound processors work on -- whether Dolby or not -- you will find that binaural recordings can provide often thrilling surround sound with surround or home theater systems. We find it cleaner and more natural than most specially-encoded Dolby Surround CDs. If your processor has the Pro Logic function, turn it off for best results if you are able to (unless it's the new Pro Logic II circuit, which works well). Totally passive Haefler-type surround processors such as the PhaseAround, Chase or Dynaco are also excellent when using binaural sources.

Why don't stereo recordings on speakers approach the realism of binaural on headphones? -- they're also two separate channels.

With any two signals fed to a pair of loudspeakers, whether stereo or binaural, there will be mixing in the room of the left and right channel sounds. The left channel sound reaches the right ear with a short delay around the front of the head, and the right channel sound reaches the left ear in a similar way. This acoustic mixing destroys much of the realism of stereo recordings and is being addressed now via a number of different "transaural" processes that attempt to cancel out the extra signal paths either in the original recording or in the final listening situation.

However, listening to stereo source material on headphones doesn't give the proper effect either, because the mikes are usually placed much further apart than the average seven inches of our ears, and without the pinna and other features of a dummy head. The end result is that most stereo recordings sound as though half the band or orchestra is huddled at your left ear inside your head and the other half is piled up at your right ear, with nothing between. (The HeadRoom headphone amp fills in some of this void, but the sound is still inside your head.) The fact is that 200 million people listening via stereo headphones are nearly all listening to material that was never intended for headphone listening! Binaural recordings are specifically intended for headphone listening for the full effect, yet not only sound great via speakers but provide excellent surround sound capabilities (see above FAQ). Prof. Stanley Lipschitz of the University of Waterloo Audio Research Group observed, "Stereo recordings should carry a warning sticker stating NOT CORRECT FOR PLAYBACK VIA HEADPHONES."

What other gear besides headphones is needed to listen properly to binaural?

No special equipment of any sort is required to enjoy binaural recordings or broadcasts -- just a binaural source and a pair of stereo headphones. It is a democratic sort of technology in that regard. High-end components are not needed to appreciate the startling realism of binaural sound; think back to the 1881 Paris experiment -- the telephone is far from hi-fi today and you can imagine what it must have been like then! Yet the binaural effect was marvelled at by all subscribers. An extended frequency response is not vital to the binaural effect, although of course the better quality the phones the better the music will sound. The headphone jacks on most components -- even high end models -- are frequently under-powered since this feature is usually an afterthought of the designers, not a primary function. Many of the better headphones will really sing when they are powered from a dedicated Headphone Amplifier. Some of these use Class A circuitry, which gives the cleanest amplification (but which in a larger amp to power speakers would carry an exorbitant cost). A number of models are available, from such sources as HeadRoom, McCormack, Melos, Krell, AKG and EarMax.

What headphones do you recommend buying or staying away from?

I have found only two models of headphones that seem to compromise the binaural effect, and those are the Sony MDR-V6 and V7. Other Sony phones are fine, even inexpensive ear bud types. The new Sony CD3000 is one of the very best headphones for either binaural or stereo that we have ever auditioned. Though it is a closed-ear type, it is extremely comfortable because the drivers do not press on the outer ears. I have found that headphones with drivers that sit away from the pinna rather than pressing on them aid in locating the sounds outside of one's head. These include the AKG K-1000, the Jecklin and the new Ergo from Precide. Though they sit on the pinna and are somewhat uncomfortable as supplied, the entire Grado line of headphones is also excellent for binaural, even their least expensive models (I highly recommend the SR-80 and SR-325). Comfort can be increased greatly by replacing the supplied foam pads with the yellow pads for the Sennheiser Model 414s. Also excellent are the top models of the Beyer and Sennheiser lines.

[The Grado Signature line has been replaced by the Reference; Stax headphones are again available on a limited basis - primarily from Audio Advisor, but not their top-of-line Omega as yet.] If you are without any headphones and your speakers are moveable, you can get much of the binaural effect by turning them to face one another and sitting or lying between them. Another approach (though a bit unwieldy) is use of a sound-absorbent panel between the closely-spaced speakers, running all the way up to your head to prevent leakage of each channel's signal into the unintended ear. This is known as Ambiophonics; more information on their interesting web site: http://www.ambiophonics.org

Say, I just realized the jack for my multimedia computer speakers looks like the one for the mini-plug on headphones. Can I plug my headphones directly into my computer audio out and play binaural CDs on my CD ROM player?

Absolutely! In fact, why the whole multimedia industry is wasting time, money and desk space on those lousy-sounding little computer speakers instead of just plugging in some stereo headphones is a great mystery to us! After all, you're not going anywhere when you're sitting here right in front of your monitor, are you? And the sound quality on both binaural and stereo with even modest headphones is going to be 100% better than any multimedia speakers. (Just don't get up suddenly, forget you're wearing headphones, and strangle yourself.)

You've got my curiosity. How can I sample a couple of these special recordings?

The easier way is to just click over to our BINAURAL DEMOS Page and download some short and startling MP2 and MP3 binaural samples for instant experiencing (after downloading of course).

There are a number of binaural CDs and cassettes but most are from rather obscure sources and if you go into a CD shop asking if they have any binaural recordings a blank stare is guaranteed. Some CDs that are true binaural do not clearly state they are on the jewel box. The simplest and perhaps most shocking demo recording of binaural can be had for around $9 at almost any large chain bookstore: go to the Simon & Schuster Audio Book rack and look for Stephen King's "The Mist" on cassette; it's also now available in a CD version. This hour-long audio drama production has a cast of 30 actors with music and amazing sound effects. Lean back in your Barcalounger, put your feet up, dim the lights and/or close your eyes (but not your ears). Monsters will creep up on you, wind themselves down from the ceiling, and people will whisper in your ears. This is better than any Stephen King movie because you are personally creating the scenes in your own mind's eye!

There have been only a few binaural recordings of a full symphony orchestra thus far. The most successful is on a binaural sublabel of Newport Classic called AUracle. I was present at the recording session with the Pasadena Symphony (top Hollywood studio musicians) and conductor Jorge Mester. They recorded Richard Strauss' Also Sprach Zarathustra together with the Saint-Saens Organ Symphony -- a pair of sonic blockbusters in any format. The Neumann dummy head hovered above and about a dozen feet behind the conductor's own head and picked up everything in the auditorium -- and I mean Everything. Recording engineers have problems with the very low noise floor of digital recording in stereo and having to quiet small sounds that previously went unnoticed. Well, with binaural recording it's even more so. I carefully adjusted my chair at one point and spoiled a take!

The recording was made directly to 20-bit computer hard drive without tape. (It is rave-reviewed on the very last page of the December 1996 AUDIO magazine). After the limited edition gold CD was released a press presentation was held in the same auditorium and the CD was played back through a pair of loudspeakers on the same stage where the symphony had recorded. The result was a demonstration of the total compatibility and realism of binaural recordings for speaker playback. A second binaural session with the Pasadena Symphony was held to record Stravinsky's Rite of Spring and the Rachmaninoff Symphonic Dances on a gold CD. It is available as CD C-20, is just as excellent if not better, and at a lower price than the first! See our Classical offerings.

NOTE: A new normally-priced pressing of the Strauss/St.-Saens Pasadena Symphony binaural CD is now available (C-18 in Classical).

Is there a single source for these elusive binaural recordings?

Absolutely, and the easiest way to access that is right here at THE BINAURAL SOURCE, which offers about 130 recordings of classical, organ, chamber music, solo, jazz, folk, rock, audio drama and sound environments. This mail order and web service grew out of John Sunier's weekly national radio program AUDIOPHILE AUDITION, on which he produced two special All Binaural Broadcasts annually for over 13 years.You may also snail mail to us at Box 1727, Ross, CA 94957.

Why are some of these CDs more expensive than most in stores?

There are several reasons. They are primarily imports from Germany, with rising Mark vs. U.S. dollar rates, plus high shipping costs for the relatively small quantities we purchase at this time. All the AudioElectronics are Limited Edition, individually-numbered CDs, pressed in small quantities due to the so-far small niche that binaural has in the recorded music field. The small quantities necessarily mean higher costs.

In spite of this, we are offering them now at the lowest prices at which they have ever been available. (In Europe, most CDs in stores normally are priced nearly double the U.S. price for the same CD!) Some of the CDs are Limited Edition Gold CDs. Your support of binaural will mean that domestic record producers will be encouraged to release more binaural CDs of U.S. artists recorded in the U.S. at standard CD prices. It is already beginning and we have been able to also lower the prices on some of the imports due to increasing customer response. We now also include some budget CDs.



***Actual binaural demos at this site using MP2 & MP3! Right Here! Just download, plug in your stereo headphones, and your jaw will drop -- we guarantee! Hearing is believing!

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