Item

Description

FFT size

Choose a setting from the drop-down 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 128-point and 2048-point 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 drop-down 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.