Wave Field Synthesis - Procedural Advantages

Procedural Advantages

By means of level and time information stored in the impulse response of the recording room or derived from a model-based mirror-source approach, a sound field with very stable position of the acoustic sources can be established by wave field synthesis. In principle, it would be possible to establish a virtual copy of a genuine sound field indistinguishable from the real sound. Changes of the listener position in the rendition area would produce the same impression as an appropriate change of location in the recording room. Listeners are no longer relegated to a "sweet spot" area within the room.

The Moving Picture Expert Group standardized the object-oriented transmission standard MPEG-4 which allows a separate transmission of content (dry recorded audio signal) and form (the impulse response or the acoustic model). Each virtual acoustic source needs its own (mono) audio channel. The spatial sound field in the recording room consists of the direct wave of the acoustic source and a spatially distributed pattern of mirror acoustic sources caused by the reflections by the recording room surfaces. Reducing that spatial mirror source distribution onto a few transmitting channels causes a significant loss of spatial information. Much more accurately this spatial distribution can be synthesized by the rendition side.

Concerning the conventional channel-orientated rendition procedures, WFS provides a clear advantage: "Virtual panning spots" called virtual acoustic sources guided by the signal content of the associated channels can be positioned far beyond the material rendition area. That reduces the influence of the listener position because the relative changes in angles and levels are clearly smaller as with closely fixed material loudspeaker boxes. This extends the sweet spot considerably; it can now nearly cover the entire rendition area. The procedure of the wave field synthesis thus is not only compatible, it clearly improves the reproduction for the conventional transmission methods.