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Zone segmentation for stereo array deployments
HOLOPLOT’s Optimized Coverage Beams allow each Array to cover the entire audience area, ensuring that both arrays are audible across the entire space width. This approach significantly improves upon conventional audio solutions by expanding the stereo “sweet spot.” However, a potential issue arises in the time domain when trying to cover the entire width of an audience area. The precedence effect dictates that if the arrival times of sounds from two audio sources differ by less than 50 ms, they are perceived as a single auditory event. If the difference exceeds 50 ms, they are perceived as separate events.
A difference greater than 50 ms results in a clearly audible echo. To mitigate this, it is advisable to segment the audience area. This approach ensures that each array does not cover the entire width of the audience area, thereby minimizing the time difference and preventing the perception of echoes.
To determine if there is a requirement for the audience area/s to be segmented, the arrival times at the point where the distance between the two arrays is greatest need to be calculated; we will call this the reference point. This will almost always be one of the front corners of the area/s. This can be calculated using the equation:
dL | Distance from the acoustic centre of the left array to the reference point |
dR | Distance from the acoustic centre of the right array to the reference point |
c | The speed of sound (344 m/s) |
tL | Arrival time at the reference point for the left array |
tR | Arrival time at the reference point for the right array |
tΔ | Difference in left and right array arrival times |
We will now work through an example of a stereo setup to determine whether we need to consider using zone segmentation within HOLOPLOT Plan.
Using the draw polygon tool, we can measure the distance from the acoustic center of the left array to the front right corner of the audience area. This is
25.3m.
We will then measure the distance from the acoustic center of the right array to the same reference point, which is
9.42m.
Using the equation above, we obtain tΔ=(25.3/344)-(9.42/344), which gives us an arrival time difference of 46.17 m/s. Therefore, we can cover the whole width of the audience area with both arrays and there is no need for segmentation.
When the arrival time difference is greater than 50 m/s there are two main options for how an audience area can be segmented. These are known as.
The best method depends on the system's purpose. Split coverage segmentation is best for stereo and music, as the stereo image is maintained across most of the audience area. Only the areas where arrival timing could be an issue are not included. Half coverage is best for speech applications or mono content delivery, where there is no requirement to maintain a stereo image.
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