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. Add a
Color Expression or
Energy Decay subnode as needed. The impulse response plot reconstructs the impulse response based on a Ray Acoustics simulation.
From the Source list, choose
Dataset (the default) or
Function.
If you chose Dataset, from the
Dataset list, choose an applicable dataset or
None. The default option,
From parent, uses the dataset from the parent plot group node. Only the
Receiver 2D and Receiver 3D datasets are valid for this specialized plot.
If you chose Function, choose an applicable functions or
None from the
Function list. Click the
Refresh button to update the list of functions.
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.
For all text fields, click the Replace Expression (
) button to select a predefined quantity and replace the entire contents of the field.
From the Transformation list, choose a transformation of the data on the
x-axis:
None (the default) for no transformation, or
Discrete Fourier transform. If you select to display a discrete Fourier transform (DFT), choose one of the following options from the
Show list:
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Real part, to show the real part of the output only.
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Imaginary part, to show the imaginary part of the output only.
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Amplitude, to show the amplitude of the output (the default).
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Phase, to show the phase of the output.
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Frequency spectrum, to display the function’s frequency spectrum by computing the number of frequencies and the frequency range based on the FFT (fast Fourier transform) of the function. The transform is valid for all functions, but what you get corresponds to a periodic continuation of the function outside the chosen bounds. To specify these values manually, select the Number of frequencies check box and enter a value in the associated field (the default is based on the number of time samples). From the Scale list, choose None (the default), Multiply by sampling point, or Divide by number of frequencies. You can choose to scale with the sampling period to show Fourier transform values instead of a pure DFT transform. Select the Scale check box to scale the values on the y-axis so that their magnitude reflects the magnitude of the original signal. The values then have the same unit as the input data for the FFT. For a pure sinusoid, the scaled value is the peak magnitude divided by the square root of 2 ( ). Select the Frequency range check box and then enter the bounds of the frequency range in the Minimum and Maximum fields (in Hz). The FFT algorithm uses resampling based on linear interpolation. The x-axis shows the frequency (in Hz). By default, the y-axis shows the unscaled Fourier coefficients.
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If you have selected Amplitude or
Frequency spectrum, you can select the
In dB check box to present the values in dB. From the
dB type list, choose
10log (the default) or
20log. The display in dB requires a reference value. From the dB reference list, choose
Maximum (the default) to use the maximum value as the reference, or choose
Manual to enter a suitable reference value in the
Reference value field.
If you have selected Real part,
Imaginary part,
Amplitude, or
Phase, the following additional settings are available: To specify this value manually, select the
Number of uniform samples check box and enter a value in the associated field. If desired, select the
Inverse transform check box to use an inverse DFT. Select the
Mask DC check box to set the DC value (zero frequency component) to zero (not available if
Inverse transform is selected). The
Ignore last sample check box is selected by default to not include the last sample in the transform (not available if
Inverse transform is selected). The
Shift zero frequency and
Scale with sampling period check boxes are selected by default. Clear one or more of these check boxes if you want to exclude those steps.
In this section, only available if you have selected Discrete Fourier transform from the
Transformation list above, you can add a moving average when analyzing an impulse response plot in ray acoustics. To do so, select the
Moving average check box. You can then choose
Linear (the default) or
1/n octave from the
Type list to choose the type of moving average. For the latter option, also specify
n as a positive integer (default value: 1).
Select to Remove noncausal signal (not 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.
Select Use fully randomized phase (not selected per default) to switch the impulse response generation to the legacy method where a random phase is applied to all rays. In contrast, the default method bases the phase on the number of reflections. The default method leads to consistent values for the direct sound.
From the Display list, choose what to show:
Broadband (the default),
Individual bands, or
Filters. Choose
Individual bands to see the signal of each band separately and how they are separated in frequency.
Select the Filter kernel as either the
Brick-wall with Kaiser window (the default) or
User defined.
For User defined, if desired, enter an expression of the kernel itself in the time domain in the
field. For an FIR filter it is usually a filter (by default,
hB) multiplied by a window function (by default,
wK). These default factors are defined in the
Parameters table below. Also, if desired, enter expressions for the kernel expression using the definitions in the
Parameters table. The default parameters set up the Brick-wall with Kaiser window filter.
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
Label and
Solution check boxes to control what to include in the automatic legends (by default it includes the solution 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. If
Evaluated is selected, you can use the
eval function to create an evaluated legend text in the
Legend field that include evaluated global expressions such as global parameters used in sweeps. For the numerical evaluation, you can control the precision in the
Precision field (default: 3).