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Frequency Axis Scaling

There are two basic types of frequency axis scaling: Narrowband and Octave.  Narrowband scaling can be displayed in either Linear or Logarithmic format; Octave scaling is always displayed in Logarithmic format.

Narrowband Scaling

The spectrum produced by an  FFT algorithm is also known as a narrowband spectrum.  Each spectral line is a constant bandwidth and typically quite narrow.  This narrowband spectral data can be displayed on either a linear or logarithmic scale but the frequency resolution is determined by the sampling rate and FFT size and remains unchanged.

Octave Scaling

Octave scaling produces a set of bands with constant proportional bandwidth.  You can select from a range of octave formats.  1/1 and 1/3 octave are the most commonly used formats.  See the Octave Scaling topic for more details.

See Also:  Amplitude Axis Scaling, Scaling