Impulse Response
Add an Impulse Response subnode () to a 1D plot group to create an impulse response plot. After defining the characteristics of the impulse response, click Plot () to create the impulse response plot. If you want to add color to the impulse response, add a Color Expression subnode. The impulse response plot reconstructs the impulse response based on a Ray Acoustics simulation.
For details on setting up a Ray Acoustics model and postprocess the impulse response, see Impulse Response and Receiver in the Acoustics Module User’s Guide.
Go to Common Results Node Settings for links to information about these sections: Title and Coloring and Style.
Data
From the Data set list, choose an applicable data set or None. The default option, From parent, uses the data set from the parent plot group node. Only the Receiver 2D and Receiver 3D data sets are valid for this specialized plot.
From the Frequency interpretation list, choose an interpretation of the frequency: Octave (the default), 1/3 octave, or 1/6 octave. This selections should coincide with the frequency interpretation used in boundary conditions and sources in the underlying Ray Acoustics simulation. The frequency content and resolution of the impulse response are based on this selection.
Expressions
Set up the variables that are necessary for reconstructing the impulse response. In practice these variables are used to define and add the contribution of each ray that intersects the receiver data set to the impulse response.
•
Define the frequency variable for the rays (SI unit: Hz) in the Frequency field. The default is rac.f.
•
Define the power variable for the rays (SI unit: kg·m2/s2) in the Power field. The default is rac.Q.
•
Define the density (SI unit: kg/m3) in the Density field. The default is rac.rho.
•
Define the speed of sound (SI unit: m/s) in the Speed of Sound field. The default is rac.c.
For all text fields, click the Replace Expression () button to select a predefined quantity and replace the entire contents of the field.
x-Axis Data
From the Transformation list, choose a transformation of the data on the x-axis: None (the default) for no transformation, or Frequency spectrum. For a frequency spectrum, the following properties are available:
Select the Number of frequencies check box and enter the number in the associated text field.
For a frequency range, select the Frequency range check box and defined the range using the Minimum and Maximum fields (SI unit: Hz).
Select the Scale check box to transform the frequency spectrum so that it has the same scale as the original data.
Advanced
The following settings are available to control the Kaiser-Bessel window functions that are used to reconstruct the frequency content of the impulse response. Each ray contributes with an amplitude, arrival time, and frequency content to the time-domain signal.
•
Define a sampling frequency (SI unit: Hz) in the Sampling frequency field. The default is 44100.
•
Define a ripple factor in the Ripple factor field. The default is 0.05.
•
Define a passband slope factor in the Passband slope factor field. The default is 1.03.
Select to Remove noncausal signal (selected per default). This options removes the unphysical parts of the impulse response signal that appear before the arrival time of the first ray. This part is generated due to the nature of the window functions used for the signal reconstruction.
Legends
The Show legends check box is selected by default to display the plotted expressions to the right of the plot. In plots where each line represents a certain time value, eigenvalue, or parameter value, these values are also displayed.
When Automatic is selected from the Legends list (the default), select or clear the Description, Expression, and Unit check boxes to control what to include in the automatic legends (by default it includes the description only). You can also add a prefix or a suffix to the automatic legend text in the Prefix and Suffix fields. If Manual is selected from the Legends list, enter your own legend text into the table.