To determine the frequency components of a sound, octave band analysis in which frequencies
are segmented into proportionate widths (octave bands) is used. In a standard full-octave plot,
each band occupies a bandwidth that is twice as wide as the previous band and half as wide as
the next band.
Octave analysis corresponds to the way how people perceive sounds because it lets you
compare signal levels across broad frequency ranges. Breaking frequencies into octaves helps
you measure the subjective qualities of sound.
To get a better frequency resolution, each octave band can be divided into 3 bands. This is called 1/3 octave plot and is available as a separate function in SIGVIEW.
Both Octave and 1/3 Octave plot functions can be found in a "Signal tools" menu.
Both Octave plot functions are implemented by using Custom
Filter bank plot
function and not by
using FFT. This is required by the various technical standards defining octave plot calculations.
Filter bank definition files can be found in the "filters" subdirectory of the SIGVIEW application
data directory. The files are named "octave_filter.flb" and "1_3_octave_filter.flb". As for all custom
filter bank plots, you can freely change the frequency values in these files by using any text
editor. For details, see the custom filter bank
By default, Octave plots are displayed by using histogram display type (min-reference). As for all
other plots, you can change the display type by using a context menu or toolbar buttons (Display