Contents Signal Analysis » Spectral Analysis » Spectrum Calculation DetailsPrint page Spectrum Calculation Details This section describes the different types of spectra available in Sound: Analysis and Specification (SAS) and details of their calculation. This section contains the following topics:Narrow Band SpectrumA narrow band spectrum is a spectrum calculated using a Fast Fourier Transform (FFT), and hence provides an analysis of the signal energy within narrow frequency bands (the width of these bands depends on the chosen length of the FFT).AutospectrumAutospectrum is a method used to estimate the power spectrum.Autospectrum (Peak)Instead of averaging all the FFT spectra, this variant of the autospectrum keeps the maximum magnitude at each frequency across all the spectra.RMS SpectrumThe RMS spectrum has a similar calculation procedure to the Autospectrum. The only difference is the applied normalization factor, which compensates for the effect of the analysis window in a different way. RMS Spectrum (Peak)Instead of averaging all the FFT spectra, this variant of the RMS Spectrum keeps the maximum magnitude at each frequency across all the spectra.Power Spectral Density (PSD)Power Spectral Density (PSD) is a way of creating the spectrum not only as a power but as a power density.Octave and Third Octave SpectrumAn octave or third octave spectrum is a way of analyzing the energy content of a signal within specific frequency bands (see Octave and Third Octave Bands). « Changing the Unit of a SpectrumNarrow Band Spectrum »
