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The reproduced recording presents an illusion of a live performance. This performance will be perceived as having existed in reality, in a real physical space; as the human mind will conceive of any human activity in relationship to their own physical experiences. The recording will appear to be contained in a single, perceived physical environment. Within this perceived space is an area that comprises the sound stage.
The sound stage is the location within the perceived performance environment, where the sound sources appear to be sounding. The sound stage will appear to be contained within a single, global environment. The sound sources of the recording will be grouped by the mind, and will appear to occupy a more or less specific area of that global environment; this area is the sound stage. It is possible for different sound sources to occupy significantly different locations within the sound stage.
Imaging is the perceived lateral location and distance placement of the individual sound sources within the sound stage. Imaging is defined by the perceived physical relationships of the sound sources. As such, it is the perceived locations of the sound sources within the stereo array and with respect to perceived distance.
The stereo (lateral) location of a sound source is the perceived placement of the sound source in relation to the stereo array. Sound sources may be perceived at any lateral location within, or slightly beyond, the stereo array.
Phantom images are sound sources which are perceived to be sounding at locations where a physical sound source does not exist. Imaging relies on phantom imaging to create lateral localization cues for sound sources. Through the use of phantom images, sound sources may be perceived at any physical location within the stereo loudspeaker array, and up to 15° beyond the loudspeaker array. Stage width (sometimes called stereo spread) is the area that spans the boundaries established by extreme left and right images of the sound sources.
Phantom images not only provide the illusion of the location of a sound source, they also create the illusion of the physical size of the source. Two types of phantom images exist: the spread image and the point source.
The point source phantom image is a focused, precise point in the sound stage where a sound source appears to be located. It is an exact location where the sound source is perceived as occupying. It appears to have a physical size that is quite narrow, and precisely located in the sound stage.
The spread image appears to occupy an area. It is a phantom image that has a size that extends between two audible boundaries. The size of the spread image can be considerable; it might be slightly wider than a point source, or it may occupy the entire stereo array. The spread image is defined by its boundaries; it appears to occupy an area between two points. At times, a spread image may appear to have a "hole in the middle," where it might occupy two equal areas, one on either side on the stereo array.
The perceived lateral location of sound sources can be altered to provide the illusion of moving sources. Moving sound sources may be either point sources or spread images. Point sources that change location most closely resemble our experiences of moving sound sources.
The listener will perceive two types of distance cues from the recorded music:
(1) the distance of the listener to the sound stage, and
(2) the distance of each sound source from the listener. Both of these distances rely on a perception that the entire recording occupies a single, global environment. This perceived performance environment establishes a reference location of the listener, from which all judgments of distance can be calculated.
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