Changing Spectrum Analysis Settings 

Click the Settings button in the Spectrum Analysis window to display the Spectrum Settings dialog. This dialog contains controls to determine how spectral information is calculated and displayed.
Item 
Description  
FFT size 
Choose a setting from the dropdown list to set the size in samples of the analysis window and number of discrete frequencies analyzed. Higher numbers produce increased frequency resolution at the expense of lower time resolution and longer computational time. The following example illustrates the results of 128point and 2048point FFT sizes on a 44,100 Hz sound file:
 
FFT overlap 
Specify the percentage of overlap between FFT analysis windows. Overlapping allows for more accurate analysis. Lower settings decrease the number of distinct analysis functions performed, which decreases processing time. High settings allow for more analysis, but can result in slow processing.  
Smoothing window 
Choose a setting from the dropdown list to determine the window function applied to the input data before analysis. The window function affects the sharpness of peaks in an FFT graph and the leakage into neighboring frequencies. The effects of these windows can be easily seen by analyzing a single sine wave:
 
Slices displayed 
The Spectrum Analysis window can display up to 64 spectrum graphs, each representing a point in time. Type a value in the Slices displayed box to specify the number of FFT slices displayed. Each slice represents FFT size samples in time. When displaying multiple slices, click the Forward or Backward radio button to determine whether slices are layered in chronological order. When Forward is selected, the first slice is displayed in the foreground; when Backward is selected, the last slice is displayed in the foreground. In the spectrum graph, drag the Slice slider to show or hide graphs from the display.
 
Set sonogram resolution 
Select the Set sonogram resolution check box and specify the number of FFT samplings used in the sonogram. When this check box is not selected, the number of samplings is determined by the length of the selection and the FFT overlap setting. Increasing the samplings increases the horizontal graph resolution but requires more processing time.  
Display Range 
The Display Range controls allow you to adjust the range of each graph.
 
Hold peaks during monitoring 
Select this check box if you want to mark the highest value of each frequency bin.
 
Maintain last monitored view 
Select this check box if you want to maintain the state of the spectrum graph when you stop playback. If this check box is not selected, the graph will revert to the cursor position. 