Point Time Fourier Transforms

Update Interval

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

Specifies which type of filter 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. These functions are all 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.

Power Spectral Density (Pa^2/Hz)

Frequency-domain description of the signal power.

Power Spectral Density (dB/Hz)

Sound pressure in decibels per hertz. Adds the Sound Pressure node.

Sound Pressure Level

Sound pressure in decibels. Adds the Reference Sound Pressure node.

Root Mean Square

The square root of the Power Spectral Density.

A-Weighted Sound Pressure Level

Weights the Sound Pressure Level with the A-scale function, for loudness less than 55 phons (at 1000 Hz, 1 phon = 1 dB). This function is typically for problems that involve the frequency range for human hearing. Adds the Reference Sound Pressure node.

B-Weighted Sound Pressure Level

Weights the Sound Pressure Level with the B-scale function, for loudness of 55-85 phons. Adds the Reference Sound Pressure node.

C-Weighted Sound Pressure Level

Weights the Sound Pressure Level with the C-scale function, for loudness greater than 85 phons. Adds the Reference Sound Pressure node.

Re{FFT Coefficients}

The real parts of the FFT coefficients for positive frequencies.

Im{FFT Coefficients}

The imaginary parts of the FFT coefficients for positive frequencies.

Phase{FFT Coefficients}

The phases of the FFT coefficients ($[Im/\mathrm{Re}]$) for positive frequencies.

Abs{FFT Coefficients}

The absolute values of the FFT coefficients ($\sqrt{{|\mathrm{Re}|}^2+{\left|Im\right|}^2}$) for positive frequencies.

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 feature allows for smooth transitions between blocks. This property can be set with a slider.

Window Function