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3D binaural stereo (BAS)

 

The human ear is a unique signal analyzer with high resolution in the time, level, and frequency domains. Depending on the direction of incidence, the ear weights sound signals according to time difference, loudness, and sound spectrum. The brain combines this complex information from both ears to create a comprehensive (binaural) auditory impression. Findings in psychoacoustics now show us that conventional acoustic recording methods cannot do justice to the binaural signal processing of our sense of hearing. Thus, essential information is lost, and the spatial arrangement of sound sources is reduced to the right/left horizon.

Conventional sound engineering

Conventional sound technology now invests immense effort in creating the spatial auditory impression in multimedia, virtual reality, or in cinemas. Digital Surround 5.1, DTS, and SDDS, with now 7 + 1 speakers, are currently state-of-the-art, and developments will continue until we are eventually surrounded by any number of selectively controllable tweeters, midrange speakers, and woofers. Intensive experimentation and research on this topic is already underway today under the term wave-field synthesis.

Increasingly, artificial levels are being inserted between the origin of a sound event and its reproduction. The auditory result is correspondingly artificial. Our listening habits follow this trend only too readily – psychology and behavioral science know the reasons for this: Even in the animal kingdom, exaggeration is often more appealing than the original. Accordingly, both manufacturers and consumers are increasingly investing in the illusion of sound.

Binaural sound engineering

The development of conventional sound technology is, to put it simply, the optimization of a makeshift technical solution from the early days of stereophony. A completely new approach was presented at the World Exhibition in Paris in 1886 and revived and further developed by Sennheiser in 1969: binaural stereo (BAS). The simple "trick" here consists in placing two high-performance microphones in a so-called "dummy head" at the location of the eardrums, i.e., where the acoustic signal is most easily perceived. The pinna and external auditory canal, as well as the resonance behavior of the artificial head, are modeled as closely as possible to the human head. In the 1970s, broadcasters, in particular, experimented extensively with BAS in the areas of radio drama and music.

This perceptually authentic, now highly sophisticated technology is used specifically in the areas of sound analysis in automotive engineering and aviation. Room acoustics are authentically reproduced and can be technically analyzed in their three-dimensionality. Measurement applications include, for example, aurally accurate, binaural measurements of sound events at very low levels, sound design, or quality control.

The BAS sound recording process, which today meets the highest technical standards, can also be used for the production of acoustic music recordings. Live concerts or studio recordings with acoustic (unamplified) instruments, from soloists to chamber ensembles to large orchestras, are ideal for this purpose (→ Audio samples).

The authentic surround sound of the BAS offers the listener an incomparable listening experience, the fidelity of which can "shock" some people the first time they hear it. In the context of music, the term holophony has been coined to describe conventional stereophony due to the three-dimensional impression.

With BAS, the playback format plays a key role: True authenticity can understandably only be achieved when the sound event is reproduced close to the eardrum. Open or semi-open headphones are best suited for this. However, even when played back through the speakers of a stereo system, almost equivalent sound authenticity can be achieved today by using a so-called crosstalk compensation.

Like many things, authentic surround sound is a matter of taste and, above all, listening habits. Knowledge of the background of this recording technology will make the listening experience more conscious and sensitize the senses. This method of music reproduction is gaining increasing traction. Especially in circles where the musical experience is paramount, the BAS is considered an insider tip.

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