3D binaural stereo

The human ear is an unique signal analyser with high resolution in respect of time, level and frequency range. Depending on the angle of incidence, the ear assesses sonic signals by interaural time difference, sound level and sound spectrum. The brain combines the complex information from both ears (binaural) to create an extensive auditory experience. Nowadays psycho acoustical research shows that conventional recording methods can hardly ever meet the requirements of the binaural signal processing which distinguishes the human sense of hearing. Thus, vital pieces of information are lost during the recording process, the spatial layout of sonic sources will be reduced to the right-left horizon.

Conventional audio engineering expends immense effort to reproduce spacial effects in Multimedia, Virtual Reality or in the cinema. Dolby Surround 5.1, DTS und SDDS with 7 + 1 speakers by now, is currently state of the art and this tendency will continue until we are surrounded by an infinite number of separate triggered tweeter cones, mid-range units and a subwoofer. There's already been a lot of experiments and research under the term “Wellenfeld synthesis”.

More and more synthetic layers will be inserted between the sound source and its reproduction whereby the results become increasingly artificial. In time, our listening habits will adapt themselves to the available synthetic products – psychologists and behavioral analysts understand the reason for this behaviour well and marketing professions know only too well how to leverage it. A spiral of technical innovation and spiraling “investment“ results.

Conventional audio engineering is – so to speak – no more than an optimised interim solution based on technology dating from the beginnings of the stereo age. A completely new approach was presented already at the Universal Exhibition in Paris in 1886 and taken up again and further developed by the company Sennheiser in 1969: The Binaural Stereo (BAS). The “trick” is quite simply to situate two high performance microphones in a so called “Kunstkopf” where the ear drums are located, as it is the place where the acoustic signal is represented most simple. The auricle, the acoustic duct and the resonance behaviour of the Kunstkopf are best possible modeled on the human head. In the 1970s there have been a lot of experiments by a number of German broadcasting companies with BAS in the fields of radio play and music. “Kunstkopf”  literally means dummy head or artificial head.

This authentic 3D audio reproducing technology has since been further developed. It is particulary useful for aurally-equivalent sound analysis in vehicle and aircraft construction. The acoustic characteristics of a room can be reproduced authentically by Kunstkopf technology and the full detail of the 3D space is available for technical analysis. Typical applications include the aurally accurate binaural technical measurement of acoustic events with very low level output, sound design or the quality check.

This BAS recording methods that meet such demanding technical requirements are equally well suited for music recording. It is predestinated for live concerts or studio recording with acoustic (non-amplified, unplugged) instruments of any category, such as solo parts, chamber music or philharmonic orchestra  (→ audio samples).

The authentic reproduction of spatial resonance enabled by BAS will offer the listener a unique 3D auditory experience, which at first contact might ‘shock’ the listener in its faithfulness. In the context of music the term holophony was coined in contrast to the traditional stereophony.

The mode of reproducing BAS recordings is of particular importance: Pure authenticy is naturally only achieved by reproducing the sound near the eardrums. Best suited for 3D-experience of Kunstkopf recordings are open/semiopen design dynamic stereo headphones. Stereo loudspeakers can be used for playback as well. Nowadays the use of transaural Cross-talk cancellation enhances the result to provide effects of equal quality.

As with most sensory experiences, authentic sound reproduction is a question of  individual preferences, coupled with the listener’s skill and experience. The knowledge of the recording process and an understanding of the associated advantages, add greatly to the appreciation of BAS Kunstkopf recordings. The technique is regarded as an insider tip and this concept is gaining more and more followers – especialy amongst those for whom the musical experience itself is of primary importance.

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