Binaural Sound The first sound recordings were done through one input and playback mechanism which is considered monaural or mono sound. Locating sound in our environment and differentiating sound sources is aided by having two ears spaced apart. Having two inputs for sound helps us gather more information from our environment. The early mono recordings limited the amount of information that could be conveyed from the time of recording to the eventual playback by the listener. When British Engneer Alan Blumlein experienced a monaural recording paired with a motion picture he realized that the sound being played back was not linked to the images of the actors on screen. There was no directionality, the actors moved about on the screen but the sound stayed in one position relative to the listener in audience of these early motion pictures. It was late 1931 when Blumlein patented with his employers Electric and Musical Industries, Limited of England, or EMI, the first binaural sound reproduction mechanism: It will be seen therefore that the invention consists broadly in so controlling the intensities of sound to be or being, emitted by a plurality of loud speakers or similar sound sources, in suitable spaced relationship to the listener, the listener’s ears will note low-frequency phase differences and high-frequency intensity differences suitable for conveying to the brain a desired sense of direction of the sound origin. It must be understood that the controlling of intensities of a plurality of loud speakers paced, for example round a motion picture screen has previously been proposed and no novelty for mere intensity control per se is claimed, except insofar as the nature of the control is such as to provide the necessary phase and intensity difference sensations. If the sound is first recorded and subsequently reproduced from the records, the control may be wholly effected either during the recording or during reproduction, or may be partially carried out in each stage. Its obvious from this patent that Blumlein saw the possibility of more than two loud speakers predicting the emergence of Quadrophonic (4 speaker) sound, 5.1 Surround Sound (5 speakers + subwoofer) and the even greater plurality of 6.1 and 7.1 surround. Blumlein acknowledges predecessors, but these early experiments did not have multiple sound inputs in the initial recording so the varied intensity of multiple speakers would do little to achieve the desired realism. It was Blumlein who realized that a sound source should be recorded as close to the way a human with two ears experiences it, if the eventual experiencer of the recording is to be given the best chance at recreating the sonic environment at the time. As he puts it, 'necessary phase'. Duen Hsi Yen explains recent efforts to perfect binaural sound, which by the way, is sometimes called stereo too; this from his 'Binaural, 3D, Holographic sound page' One way to make binaural recordings, is to install a pair of microphones into a dummy head modeled after a real human head, one located in each ear. Notable examples include: Fritz, KEMAR, Aachen - Head, B&K 4128 and Cortex. The more exact the replica, the more realistic is the binaural recording. Or you can use your own head and insert probe or miniature microphones into your own ear canals. Different pinnae sound different, and indeed certain ear shapes are better in capturing 3D sound than others. So, who has the golden ears? Just like imperfections in the lens of the eye can lead to distortions in spatial vision, similarly, imperfections in the shape of the external ear can lead to ambiguities in spatial hearing. Of course, your retina and inner ear must be in good working order too, for accurate spatial perception.