Wave field synthesis attempts to replicate a three-dimensional sound field by re-creating wave fronts moving through the entire listening area. A practical implementation of this technique usually employs many, many loudspeakers in a 360-degree horizontal array. As this patent reminds us, Huygens’ principle assumes that every point on an advancing wave front acts as the starting point of an elemental wave. Huygens’ contemporaries argued that if this were true then each elemental point would radiate backward as well as forward. Unfortunately, that is exactly what happens in the situation at hand. The illustration represents a 360-degree rectangular array, as might be used in a movie theater. The signal to each loudspeaker is synchronized with a spherical wave emanating from virtual source 900. A listener 402 near the center of the room hears the summation of all loudspeakers, including those behind him. To suppress this artifact, the patent describes a method for identifying relevant loudspeakers for each virtual source and muting the non-relevant speakers.—GLA
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