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2 How Does BACCH™ 3D Sound differ from surround sound?

BACCH™ 3D Sound has nothing to do with surround sound. Surround sound, which was originally conceived to make the sound of movies more spectacular, does not (and cannot) attempt to reproduce a 3D soundfield. What 5.1 or 7.1 surround sound aims to do is provide some degree of sound envelopment for the listener by surrounding the listener with five or seven loudspeakers. For serious music listening of music recorded in real acoustic spaces, audio played through a surround sound system can at best give a sense of simulated hall ambiance but cannot offer an accurate 3D representation of the soundfield.

In contrast, BACCH™ 3D Sound’s primary goal is accurate 3D soundfield reproduction. It gives the listener the same 3D audio perspective as that of the ideal listener in the original recording venue2. Soundstage “depth” and “width”, concepts often used liberally in hi-end audio literature to describe an essentially flat image (relative to that in BACCH™ 3D Sound), become literal terms in BACCH™ 3D Sound. If, for instance, in the original soundfield a fly cicrles the head of the ideal listener during the recording, a listener of that recording played back through the two loudspeakers of a BACCH™ 3D Sound system will hear, simply and naturally, the same fly circling his or her own head. If, in contrast, the same recording is played through standard stereo or surround sound systems the fly will be perceived to be inside the loudspeakers or, through the artifice of the phantom image, in the limited vertical plane between the loudspeakers.

Fortunately (and perhaps to some, unfortunately) flies do not generally buzz around during the recording of great musical events3. However, an acoustically recorded real soundfield is replete with the 3D cues, if not buzzing insects, that give the brain of the listener the proper information it needs to correctly perceive true depth and width of a sound image, locate sound sources in 3D space, and hear the reflections of sound and the reverbation that occur naturally in the space where the recording was made. For instance, recorded applause in a concert hall, or laughter or chatter in a jazz club, will be reproduced with uncanny accuracy, and would appear as near to the listener as they were in the original venue during recording.

BACCH™ 3D Sound allows the transmission of these recorded cues (which are critical for the perception of a realistic 3D space) by removing an artifice that occurs during playback through loudspeakers (see Q&A 10 ) and which would otherwise corrupt the natural reception of these important cues by the listener.

Surround sound does not even attempt to do that. Furthermore, surround sound, like standard stereo, is inherently plagued by so-called comb filtering problems, which are caused by the mixing of the sound waves emanating from the loudspeakers and arriving at the ears of the listener4, even if the listener is sitting in the “sweet spot”. BACCH™ 3D Sound, in addition to its primary role of reproducing the 3D soundfield, automatically corrects these comb filtering problems and flattens the frequency response at the ears of the listeners, as well as other (spectral and temporal) non-idealities of the loudspeakers, the playback hardware, the listening room (see Q&A 19 ). It even compensates for the individual features of the listeners outer ears, head shape, and torso (see Q&A 11 on customized BACCH™ 3D Sound filters), which affect the spatial fidelity of the reproduced sound.