The aim of binaural techniques is to reproduce sound exactly as it is perceived by a listener. For recording a pretend head is used, which has two microphones instead of ear-drums. The head's characteristics are replicated in detail, the microphones are placed at the top of a channel simulating the ear canal. This way the interference between the two recorded sounds is fully eliminated. Moreover, the simulation of the ear canal allows us to simulate exactly the frequency loss a sound undergoes when it enters the human ear. Even the auricle and the Eustachian tube [Human ear ] are reproduced with great attention to detail. The listening experience of these recordings must take place with ear-phones on in order to keep the simulation real. The same reproduction through a pair of loudspeakers would be ineffective due to the considerable interference between the two signals.
The Holophonic (1983) binaural recording system devised by Ego Zuccarelli adopts this kind of approach.
It's also worth while mentioning some of the recordings made on Pink Floyd's album "The Final Cut" using this technique. Even more surprising is the fact that the song "Alan's Psychedelic Breakfast" from the album "Atom Heart Mother", again by Pink Floyd, sounds like it was recorded using this technique, whereas in actual fact it was recorded well before this technique existed, in 1970, which says a lot about Pink Floyd's masterful ability in manipulating sound.
The Holophonic binaural recording system uses this kind of approach.
They allow us, starting from a signal which can even be mono, to obtain a stereo signal whose sound field extension is a quantity which can be manipulated.
The following sound illustrates an application of this kind of algorithm. Starting from a mono sound, the image progressively widens until it reaches its maximum stereophonic breadth. Then it narrows back down until it reaches its mono starting sound.
Transformation of a mono sound into a stereo sound [Track 70]
![3D Audio - Transformation of a mono sound into a stereo sound [Track 70]](/images/en/figures/layout/icona_suono.jpg "3D Audio - Transformation of a mono sound into a stereo sound [Track 70]")
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