18.4.3.1 The STFT Dialog Box

STFT stft.png
Dialog Theme See Dialog Themes.
Recalculate

See Recalculating Analysis Results.

Input

Input signal. See Specifying Your Input Data.

Specify By

Choose sampling by interval (default) or frequency.

Sampling
Interval

Specify Sampling Interval. The default (<auto>) creates an automatically-calculated interval.

Sampling
Frequency

Specify Sampling Frequency. The default (<auto>) creates an automatically-calculated frequency.

FFT Length

Specifies the size of FFT section.

Window length

Specifies window size. Must not be greater than the size of an FFT section.

Overlap

Specifies the number of data points by which the window sections overlap. Must be less than the window size.

Window
Type

Specifies the window type used by FFT. The default option is Hanning.

  • Rectangle
  • Welch
  • Triangular
  • Hanning
  • Hamming
  • Blackman
  • Gaussian
  • Kaiser

For more information, see the STFT Algorithms page.

Alpha

Only available when Window Type is Gaussian. Specifies the Alpha parameter for the Gaussian window.

Beta

Only available when Window Type is Kaiser. Specifies the Beta parameter for the Kaiser window.

Window Correction

Window Correction Factor used to correct the alteration made by applying a window to the input data. The default is Amplitude.

  • None: No correction is applied.
  • Amplitude: Amplitude Correction is applied. Used when the true amplitude of narrow band data is required. The Amplitude Correction Factor is defined as
    ACF=\frac{1}{mean(w[n])}
  • Power: Energy Correction is applied. Used when the true energy level of the data is required. The Power Correction Factor is defined as
    ECF=\sqrt{\frac {1}{mean(w[n]^2)}}
Option

Specifies the computation option. The default is Amplitude in dB.

  • Complex Result
  • Amplitude Result
  • Amplitude in dB
Swap Time and Frequency

Swap the time axis and the frequency axis in the image plot that is used for preview and output.

Output Matrix

Specify the output matrix. Results include Units, visible by selecting Matrix: Set Dimension/Labels when the output matrix window is active, then clicking on the x/y/z Labels tabs, respectively.

Create Image Plot

Only available when Option = Amplitude Result or Amplitude in dB, and Output Matrix is selected. If selected, an image plot of the result is generated.

Output Worksheet

Specify the output worksheet. See Output Results. Results include Units, visible in the Units row of the output worksheet.