Part One: Binaural: What it is and how its done.
Binaural literally means “relating to two ears”. However, when used as a recording term, binaural recording is a method of recording audio which uses a special microphone arrangement which usually replicates what a human would hear if he were in the location where the sound or sounds are being recorded.
The term was often misused as a name for stereo but binaural recording is very different from stereo recording. STEREO uses simple "left-right" information gained from relative level differences and time arrival differences of the sound entering each microphone. When done properly, a good stereo recording can present the listener with vast amounts of information including soundstage and music instrument placement. BINAURAL uses the concept of STEREO but also attempts to imprint frequency-dependent distortions of phase and amplitude that change when sound reaches the eardrums. These distortion effects vary with the direction of the sound source as well as the human body (most importantly the human head and ear).
Binaural recordings seek to replicate the to imprint frequency-dependent distortions of phase and amplitude by using what is commonly called a Dummy Head. Professional heads vary in size, quality, build, cost and most importantly, recording approach.
In most cases, the recordings done with Dummy Heads reproduce sound in such a way as to produce a three-dimensional effect which gives the listener the impression of being in the Dummy Heads place. In other words, it’s the ultimate ‘you are there – LIVE” effect. However, this effect is only able to be reproduced when the listener is using headphones. When used with loud speakers however, the realism is lost. However, a good binaural recording will sound very similar to good purist-miked stereo recordings (but without the three dimensional realism).
In the world of today, with technologies like Dolby Digital EX and DTS-ES, one would think that binaural recording is just another new trick for recording music. This is far from the truth.
Binaural 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 producing the binaural effect.
Modern day recordings are much more HI-FI and usually utilize special “dummy heads” which seek to replicate a human head and ear as closely as possible in order to achieve the best recording possible. The picture at the top of this article is just one type of dummy head.
As you can see, the dummies all look different but the recording approach is similar in general.
Most dummy heads place the microphones inside the head where the eardrum would be located and apply a special EQ preset which compensates and corrects for the sound traveling through your ear canal. (SEE BELOW) That way, when you listen to the recordings, it doesn’t have to go through the ear canal twice.
This results in the most accurate recording possible while providing 3D realism.
There are other ways to achieve binaural recordings. The second most popular method is using what is called a Jecklin Disc or Jecklin Baffle.
The idea of using an absorptive baffle between two omni directional mics was first proposed by Alan Blumlein, but was later refined and perfected by Juerg Jecklin (I think it is the same guy who makes those fugly electrostatic headphones).
Anyway, Jecklin's baffle was 300mm in diameter, made of 3/8" plywood covered with about 1" of foam and sheepskin on each side. However, the precise thickness of the baffle doesn't appear to be critical. I have tried baffles of about ½ an inch to 4 inches thick and it made little difference. The important thing to focus on with a Jecklin disc is the 165 mm (8 inch) distance between the two omni directional microphone capsules. This places each microphone to about….you guessed it, the distance of the human ears.
THE JECKLIN DISC
The third way to achieve a good binaural recording is to use yourself. That’s right, use your own head. The easiest way to do this is to place one omni-directional microphone near each one of your two ears and record the sound.
So, how do you do this yourself?
Well, I’ll tell you.
1)Buy a dummy head (you will need A LOT of $$$$$$)
2)Wait for part two of this article……