Filter
Top Products
254
USING SPECTRUM ANALYSIS CHP. 17
Smoothing window
Choose a setting from the Smoothing window drop-down list to determine the window function applied to the
input data prior to analysis. This option influences the sharpness of peaks in an FFT graph and the leakage
into neighboring frequencies.
• Choose
Rectangle to apply no window. This results in a very sharp peak, but high leakage.
• Choose
Triangular (also referred to as a Bartlett or Parzen window) to apply a window that results in less
leakage than the rectangle window.
•
Hamming, Hanning, and Blackman windows are commonly used in audio applications.
• Choose
Blackman-Harris to obtain the least sideband leakage of the six options. The major drawback of
Blackman-Harris is rounded graph peaks.
Slices displayed
The Slices displayed value determines the number of FFT slices created for the selection. When displaying
multiple slices in the spectrum graph, slices are displayed chronologically forward or backward based on
whether you have the
Forward or Backward radio button selected.
Set sonogram resolution
The Set sonogram resolution value determines the number of FFT samplings used in a sonogram. This keeps
the processing time and graph resolution constant. Increasing this value increases the horizontal graph
resolution, but requires more processing time.
When this check box is cleared, the resolution value is determined by the length of the selection and the
FFT
overlap
value.
Display range
Note:
These options are available in Normal display only.
Select the
Both, Left, or Right radio button to choose which graph you want to edit.
If you are analyzing a stereo file, select the
Sync Graphs check box to synchronize both displays in a stereo file
so you can view the same region of the FFT in both channels.
Select the
Logarithmic graphing check box to display the X-axis in logarithmic mode instead of linear mode.
This results in more graph area being devoted to lower frequencies.
Frequency minimum
Determines the lowest frequency displayed in a graph when you select
Zoom to Range.
Frequency maximum
Determines the highest frequency displayed in a graph when you select
Zoom to Range.
Ceiling
Determines the highest amplitude level displayed in a graph when you select
Zoom to Range.
Floor
Determines the lowest amplitude level displayed in a graph when you select
Zoom to Range.
Hold peaks during monitoring
Selecting this check box results in the highest value of each frequency being indicated on the spectrum
graph with a small horizontal line. The length of time (in seconds) that the peak is held is determined by the
value entered in the edit box.