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CHAPTER 7

Using SIM 3

7.5. UNDERSTANDING COHERENCE (VALIDITY OF THE MEASUREMENT)

7.5.1. Coherence Overview

The coherence threshold is the level at which the SIM 3 analyzer accepts that the correlation

of the data at the two measurement points is sufﬁcient to present that data as a trace

within the viewer at a particular frequency or subset of frequencies. Coherence is shown

as a percentage, and the higher this percentage is, the more likely the measurement at that

frequency is accurate.

7.5.2. Coherence in Frequency Response Measurements

Within every SIM 3 measurement, it is normal to see numerous peaks and dips within the

red Coherence trace, especially when using live program material as a measurement source

and when measuring at a greater distance from the loudspeakers. The dips indicate lower

coherence.

NOTE: The corresponding frequency response trace (amplitude over

frequency) is more likely to be missing or showing a sharp and usually narrow

dip in the areas where low coherence is indicated.

Figure 7.22. Frequency Response trace with Coherence trace

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Meyer Sound SIM 3 Guía de usuario Pagina 151