Average spectra

The average spectra chart represents the mean of the spectra computed for each of the directions.

During the analysis process (see the description of the technique in this manual), the windows are subjected to the Fourier transform, which therefore generates one spectrum for each window. By averaging the spectra of the windows at each frequency, for the single trace, the average spectrum is obtained. Performing the same operation for all directions produces the average spectra chart.

The usefulness of this chart lies in the possibility of verifying that there are no sources with content at particular frequencies which are at the same time periodic. In practice it provides information on the quality of the recording: a good recording should show an average spectra chart in which the spectral curves follow the same trend, so that it can be stated that there are no conditions invalidating the assumption of ambient noise sources (a peak at a particular frequency would indicate the presence of a particularly strong source that disturbs or masks the others).

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