In signal processing and statistics, the cross-spectrum is a tool used to analyze the relationship between two time series in the frequency domain. It describes how the correlation between the two series is distributed over different frequencies. For example, if two microphones are recording audio in a room, the cross-spectrum can reveal the specific frequencies of sounds (like a hum from an appliance) that are prominent in both recordings, helping to identify common sources.
Technically, the cross-spectrum is the Fourier transform of the cross-covariance function. This means it takes the relationship between the two signals over time and represents it as a function of frequency.
↑ von Storch, H.; F. W Zwiers (2001). Statistical analysis in climate research. Cambridge Univ Pr. ISBN0-521-01230-9.
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