Point-to-Point Time Fourier Transforms

Update Interval

Sets the number of time-steps after which to update the Fourier transform.

Specifies the type of filter that is applied. Digital filters allow you to filter out parts of a signal which correspond to certain frequencies.

None

Does not use a filter.

Band pass filter

Keeps frequencies between low and high cut-off levels. Adds an Ideal Filter sub-node in which you can set these levels.

Band stop filter

Discards frequencies between low and high cut-off levels. Adds an Ideal Filter sub-node in which you can set these levels.

Specifies the frequency function that is generated. All these functions are standard functions for this type of analysis.

Frequency

Frequency in Hz.

Octave Bands

Discrete frequency bands corresponding to different octaves within hearing range. Each successive band represents twice the range of the previous one.

3rd Octave Bands

Discrete frequency bands corresponding to one-third of each octave within hearing range.

Fourier Mode

The index in the Fourier calculations.

Strouhal Number

The non-dimensional version of the Frequency option. Selecting this option adds a Strouhal Number sub-node to the FT node.

Custom Bands

Lets you define a set of custom frequency bands by adding a Custom Bands sub-node to the FT node.

Start Time

The start time of the time sampling for this object.

Cut-off time

The end time of the time sampling for this object.

Clicking the property customizer button in the right-hand column activates a property customizer that lets you specify both the time value and the appropriate time units (hr, min, or s). If you have multiple FTs, you can vary the settings of this property to sample multiple time intervals from the simulation run.

Cross Spectral Density

The power spectral density of the cross-spectrum signal, $G(x_1,x_2;\omega )$ (see Eqn. (500)).

This option is comparable to the auto-spectral density of 1-point Fourier transforms, $G(x;\omega )$ (see Eqn. (499)).

Cross Root Mean Square

The root mean square of the Cross Spectral Density.

This option is comparable to the RMS of 1-point Fourier transforms.

See Frequency-Space Parseval’s Relation.

Coherence

$\gamma$ in Eqn. (506).A measure of the correspondence between the magnitude of two signals at different frequencies. Its range is 0 - 1.

Phase

$\theta$ in Eqn. (505). A measure of the offset (phase difference) between two signals. Its range is -p to +p.

Analysis Blocks

Specifies the number of analysis blocks $N_b$ (see Eqn. (523)) for this data set function to use.

Overlap Factor

Sets the overlap factor $\alpha$ (see Eqn. (523)) between blocks, if any, in a range from 0 to 0.9. This property allows for smooth transitions between blocks.

Window Function