What is Auto Spectral Density?

The Auto Spectral Density or Auto RMS spectrum analyses uses Fourier Transforms to process optionally overlapped sections of the input data. The result of each Fourier analysed section is called a periodogram. We then process all the resulting periodograms to produce a spectral result.

Standard Spectrum

This is just the ensemble average of all the periodograms. Basically all the periodograms are summed together on a point for point basis and the average value at each point is the standard spectral result

Limit Hold Spectrum

This finds the ensemble maximum level rather than the average value. All the periodograms are compared with each other on a point for point basis. The maximum value at each point is the Limit Hold spectral result.

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Dr Mike Donegan

Senior Software Engineer at Prosig
Mike graduated from the University of Southampton in 1979 and then went on to complete a PhD in Seismic Refraction Studies in 1982. Mike then joined Prosig as a special applications engineer. He spent forty years at Prosig, researching & developing new algorithms and assisting customers with data analysis issues, until his retirement in 2024.

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