US 6.3

11.4. Near Field

The options in this menu allow the user to visualize the field values at the observation points defined in the simulation parameters.

The following options are available:

  • View Cuts: Visualizes a plot of the field values with respect to the observation points cut.
  • View Cuts by Frequency: Visualizes a plot of the field values at a given point, step and speed of sound with respect to frequency.
  • View Cuts by Step: Visualizes a plot of the field values at a given frequency, point and speed of sound with respect to the parametric step.
  • View Cuts by Speed: Visualizes a plot of the field values at a given frequency, point and step with respect to the speed of sound.
  • Near Field 3D: Visualizes a 3D diagram showing the amplitude of field values at each observation point for a given step and frequency.
  • Delay Process: Visualizes the temporal evolution of the signal emitted by the ultrasound sources at an observation point, allowing the user to choose the shape of the signal.
  • Power Process: Visualizes the power of the sound waves emitted by the ultrasound sources as received by each observation point.

 

11.4.1. View Cuts

This option allows the user to visualize a plot of the sound pressure values at a given frequency, step and speed of sound with respect to the cut of observation points. When this option is selected, the following panel is shown:

View Cuts panel

View Cuts Panel

In this panel, the user can select the effects of the rays used to calculate the field, the parametric step, the frequency, the set of observation points, the order of the considered rays, the source and the speed of sound. By pressing the "Add Series" button, a new plot will be added to the panel.

It is also possible to visualize the phase of the field values by selecting the "Phase" tab in the chart panel.

The user can also manage the already added series, being able to do actions such as removing series, changing the color of series or importing and exporting series from/to text files.

 

11.4.2. View Cuts by Frequency

This option allows the user to visualize the field values at a given point, step and speed of sound with respect to the frequency. When the user selects this option, the following panel will be shown:

View Cuts by Frequency panel

View Cuts by Frequency panel

In this panel, the user can select the effects of the rays used to calculate the field, the parametric step, the set of observation points, the point, the order of the considered rays, the source and the speed of sound. By pressing the "Add Series" button, a new plot will be added to the panel.

It is also possible to visualize the phase of the field values by selecting the "Phase" tab in the chart panel.

The user can also manage the already added series, being able to do actions such as removing series, changing the color of series or importing and exporting series from/to text files.

 

11.4.3. View Cuts by Step

This option allows the user to visualize the field values for a given point, frequency and speed with respect to the parametric step. When the user selects this option, the following panel is shown:

View Cuts by Step panel

View Cuts by Step panel

In this panel, the user can select the effects of the rays used to calculate the field, the frequency, the set of observation points, the point, the order of the considered rays, the source and the speed of sound. By pressing the "Add Series" button, a new plot will be added to the panel.

It is also possible to visualize the phase of the field values by selecting the "Phase" tab in the chart panel.

The user can also manage the already added series, being able to do actions such as removing series, changing the color of series or importing and exporting series from/to text files.

 

11.4.4. View Cuts by Speed

This option allows the user to visualize the field values for a given point, frequency and step with respect to the speed of sound. When the user selects this option, the following panel is shown:

View Cuts by Speed panel

View Cuts by Speed panel

In this panel, the user can select the effects of the rays used to calculate the field, the frequency, the step, the set of observation points, the point, the order of the considered rays and the source. By pressing the "Add Series" button, a new plot will be added to the panel.

It is also possible to visualize the phase of the field values by selecting the "Phase" tab in the chart panel.

The user can also manage the already added series, being able to do actions such as removing series, changing the color of series or importing and exporting series from/to text files.

 

11.4.5. Near Field 3D

This option allows the user to visualize a 3D diagram displaying the amplitude of the field values at each observation point, given the step and frequency. When this option is selected, the following panel appears:

Near Field 3D options

Near Field 3D options

In this panel, the user needs to select the step, frequency and speed of sound they want to visualize the 3D diagram for, as well as the group or groups of observation points they want to compute the near field for. After the user has configured the parameters and pressed the "OK" button, the following panel appears:

Near Field 3D diagram

Near Field 3D diagram

The user can select whether they want to visualize the contributions of the direct rays to the field, the contribution of the scatter rays, or the total field. They can also select whether they want to visualize the results in logarithmic units (dBPa - that is, sound pressure with respect to 1 pascal in dB) or natural units (Pa). The user can also filter the displayed values within a range, by checking the "Enable Filtering" checkbox, entering the minimum and maximum values and pressing the "Filter" button.

Additionally, there are several options the user can use to alter the visualization of the results, such as possibility of hiding/showing the left panel, the observation points grid, the geometry, the axes or the sources. The user can also save the 3D diagram to an image file in a given location in their computer.

 

11.4.6. Delay Process

This option allows the user to visualize the Delay Process, that is, a visualization of the signal emitted by the ultrasound sources in the time domain, as it is received at an observation point. When the user selects this option, the following panel is shown:

Delay Process panel

Delay Process panel

In this panel, the user needs to select the step, frequency, observation point and speed of sound they want to show the results for. In addition, the user needs to select one of the multiple signal shapes:

  • Dirac Delta: A instantaneous pulse.
  • CDMA: A random distribution of pulses centred with positive (high) a negative (low) levels. Note that a low or high level is considered as a Pulse. The "Length" parameter determines the number of pulses to be generated, while
    "Pulse Width" refers to the time duration of each pulse, in milliseconds.
  • Sinusoid: A sinusoidal signal. The "Frequency" is the frequency of the sinusoidal signal, in KHz. The "Phase" is the initial phase of the sinusoidal signal, in degrees. The
    "Duration" is the total length of the generated sinusoid in the time domain, in milliseconds.
  • Tukey Envelope: A Gaussian signal enveloped by a rectangular pulse. The "Alpha Parameter" defines the slope of the Gaussian curve. The higher is this parameter, the more enveloped by the rectangular pulse is the generated signal.
    The "Pulse Width" defines the total length of the generated signal in the time domain, in milliseconds.
  • Gaussian pulse: A Gaussian pulse defined by its sigma parameter, in milliseconds.
  • Custom signal: A user-defined signal (by a user function). In this drop-down list, only functions that return a double value and accept no arguments will be shown. The user function defines the base signal function, that must be centered at t=0. This function is then multiplied by the field value of each ray, translated in time by the propagation of the ray and finally the value of all functions are added at each point to obtain the Delay Process plot.

The following is the example of a user-function that can be used as a custom signal (a square signal of amplitude 1 and 3ms long):

double square_signal(){
double tms = $t * 1000.0;
double DURATION_MS = 3;

if (tms <= -DURATION_MS/2 || tms >= DURATION_MS/2) {
return 0.0;
} else {
return 1.0;
}
}

The function used as a custom signal has access to three special variables, prefixed by the dollar symbol:

  • $t: The time value, in seconds, the function is sampled at.
  • $freq: The selected frequency, in Hz.
  • $sound_speed: The selected speed of sound, in m/s.

Additionally, the "Time (ms)" panel allows the user to specify the time interval they want to see the results for. The "Initial" and "Final" fields represent the bounds of the time interval, while the "Samples" field is the number of evenly-spaced points that will be calculated within the time interval and therefore the number of points of the generated plot.

The "Keep previous plots" option allows the user to choose whether they want to preserve the previously plotted graphs (which could be useful if the user wants to compare several plots) or they want to clear all previous plots. This option only has an effect for signals different than "Dirac Delta" (which are always shown in a different panel each time).

When the user has finished setting the parameters, they need to click on the "OK" button to plot the Delay Process results.

Only when the CDMA signal has been selected, the window represented below asks the selection of the Correlation Signal to be plotted with the following options.

  • Input (x[n]): the original CDMA signal is represented.
  • Output (y[n]): the received CDMA signal is represented
  • Correlation (c[n]): the correlation on the received signal is represented.

chose a signal window

Selection of signal to be plotted with CDMA

Plot of the delay process for a Gaussian signal

Plot of the delay process with a Gaussian signal

In the plot viewer, the user can delete or change the color of the displayed series, as well as import or export series from/to text files.

 

11.4.7. Power Process

This option allows the user to visualize the power of the emitted sound waves as received at each observation point. When the user selects this option, the following panel is shown:

Power process options panel

Power process options panel

In this panel, the user needs to select the step, frequency and speed of sound the results are visualized for. The user can select a specific source or compute the sum of the results of each one by checking the "All" option.

The "Keep previous plots" option allows the user to choose whether they want to preserve the previously plotted graphs (which could be useful if the user wants to compare several plots) or they want to clear all previous plots.

When the user presses the "OK" button, a graph like the following will appear, showing the power of the sound waves for each observation point:

Plot of the power process

Plot of the power process

 

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