Parameter  Description 
Data Source  Specifies whether this Express VI reads data from a block diagram input terminal or from a file. From terminal specifies that this Express VI reads data from a block diagram input terminal. From file specifies that this Express VI reads data from a file. This Express VI can read data from waveform, WAV, or TXT files. 
File Path Configuration  Contains the following options:
 File path—Specifies and displays the path to the file from which this Express VI reads data. This option is available only when you select From file in the Data Source section.
 Prompt to choose a file each time this VI runs—Specifies whether this Express VI displays a dialog box that prompts you to select a file each time this Express VI runs. This option is available only when you select the From file option in the Data Source section.

Method  Specifies the method to compute the spectrogram of the input signal. The default is STFT Spectrogram. Other options include Gabor Spectrogram, Adaptive Spectrogram, WignerVille Distribution, ChoiWilliams Distribution, and ConeShaped Distribution. 
TF Sampling Info  Contains the following options:
 Frequency bins—Specifies the number of bins along the frequency axis to sample the signal in the joint timefrequency domain. Frequency bins must be a power of 2 and greater than 0. To avoid consuming too much memory, this Express VI limits the maximum Frequency bins to 2,048.
 Time steps—Specifies the sampling period, in samples, along the time axis in the joint timefrequency domain. This Express VI coerces the value of Time steps so that no more than 2,048 rows exist in the spectrogram. If you select STFT Spectrogram in Method, you can consider Time steps as the step size to move the sliding window. The number of rows in the spectrogram equals the length of the signal segment you select divided by Time steps. If you specify a small value for Time steps, the spectrogram might be large, which requires a long computation time and more memory. If you need to use a smaller value for Time steps, use the sliders under the waveform graph to reduce the length of the signal segment for this Express VI to process.

Algorithm Settings  Contains the following options:
 Window type—Specifies the type of the sliding window. Window type is available only when you select STFT Spectrogram in the Method pulldown menu.
 Window length—Specifies the length, in samples, of the sliding window and controls the relationship between the time resolution and the frequency resolution. A large window length creates a better frequency resolution but a poor time resolution. Window length is available only when you select STFT Spectrogram in the Method pulldown menu.
 Reassigned—Specifies to perform reassignment for the spectrogram by moving the dispersive energy to its local center of gravity in the joint timefrequency domain. The reassignment can improve the readability of the spectrogram for some signals. Reassigned is available only when you select STFT Spectrogram in the Method pulldown menu.
 Order—Specifies how this Express VI balances the timefrequency resolution and the crossterm interference of the Gabor spectrogram. Order must be greater than or equal to 0. Order is available only when you select Gabor Spectrogram in the Method pulldown menu. As Order increases, the timefrequency resolution of the Gabor spectrogram improves, but the spectrogram will have more crossterm interference. Usually, 2, 3, or 4 is an appropriate value for Order.
 Gaussian window length—Specifies the length, in samples, of the Gaussian window of the Gabor elementary functions and controls the relationship between the time resolution and the frequency resolution of the spectrogram. Gaussian window length must be a power of 2 and greater than or equal to 8. Gaussian window length is available only when you select Gabor Spectrogram in the Method pulldown menu. As the value of Gaussian window length increases, the frequency resolution increases, but the time resolution worsens. Gaussian window length determines the other parameters of the Gabor elementary functions. The number of carrier frequencies, N, of the Gabor elementary functions is half of Gaussian window length. The oversampling rate is 4, that is, the time steps, dM, of the Gabor elementary functions equals N4. The variance of the Gaussian envelope window equals dM×N(2).
 Type—Specifies the type of the elementary function to use to represent the signal. Type is available only when you select Adaptive Spectrogram in the Method pulldown menu.
 Number of terms—Specifies the maximum number of Gaussian chirplets or Gaussian pulses to represent the signal. Number of terms is available only when you select Adaptive Spectrogram in the Method pulldown menu.
 Convert to analytic—Specifies to convert the realvalued input signal to the corresponding analytic signal. Convert to analytic is available only when you select WignerVille Distribution, ChoiWilliams Distribution, or ConeShaped Distribution in the Method pulldown menu. The analytic signal has no negative frequency components and has the same positive frequency components as the original signal. Converting to the analytic signal can suppress the crossterm interference between the positive frequency components and the negative frequency components.
 Alpha—Controls the relationship between resolution and crossterm interference. Alpha must be greater than or equal to 0. Alpha is available only when you select ChoiWilliams Distribution or ConeShaped Distribution in Method. Increasing Alpha suppresses the crossterm interference better but reduces the timefrequency resolution.

Data Type and Sampling Rate  Contains the following options:
 Data type—Specifies the data type of the input signal. Data type is available only when you select From terminal in Data Source. When you select From file in Data Source, this Express VI determines the type of input signal based on the contents of the file.
 Sampling rate—Specifies the sampling rate of the input signal in hertz. Sampling rate must be greater than 0, or this Express VI sets Sampling rate to 1 automatically. Sampling rate is available only when the input signal is a real or complex data type.

Spectrogram, Waveform, and Power Spectrum  Displays the timefrequency representation in the upper graph and the timedomain signal in the lower graph. Contains the following options:
 dB—Specifies whether this Express VI displays the spectrogram in decibels.
 Auto Z scale—Specifies to adjust the ZScale automatically.
 Spectrogram—Displays the spectrogram.
 Time Waveform—Displays the signal to process.
 Power Spectrum—Displays the power spectrum.
 Slide bar—Specifies the signal segment of interest. You can move the sliders to determine the length of the signal segment, and you can move the gray bar to slide the segment. A large segment length requires a long computation time and more memory. This Express VI limits the segment length so that no more than 2,048 rows exist in the spectrogram.
