Sources

Add, remove, edit noise sources

Multiple sound sources may be placed in the environment. A scenario may be solved in the frequency domain or the time domain, and all sources in the scenario must be solved in the same domain. A problem can contain scenarios with a combination of frequency and time domain solves.

Positioning sources

Sources may be moved by entering coordinates in the source page fields, or by clicking and dragging the source in the x and y directions with the mouse when in bird’s eye view mode press the button Reset View . The current source is selected from the dropdown menu. Sources may be added and removed with the buttons Add, Remove and Make copy.

Editing source properties

The source sound power level or time series are not set directly on this page. To edit the spectrum for a source, click on the Set spectrum button. This shows the Source Spectrum form. To edit the time series for a source, click the button Set time series, which shows the Source Time Series form. As a scenario can only contain either frequency-based or time series-based sources, changing between these types will change all sources in the current scenario.

Directivity data for the source is entered on the Directivity Form, accessed by clicking Set directivity.

Position and Source placement

Position data is stored with a precision of 0.1 m. This is true for all positional info, i.e. sources and probes. The solvers will ignore sources placed on land or in the seabed.

To temporarily disable a source without removing it, uncheck the box Source enabled.

Importing multiple sources

The button Import CSV will import a list of sources from a CSV file. There are several important restrictions on the format of the input CSV file:

The data (and every row of the data) must have 4 columns. The columns are Name, x, y, z. A header row (i.e. “Name, x , y , z”) is optional. Each subsequent row represents a single source. The Name field is a free text field, and the x, y and z fields must contain numbers, and will be interpreted as feet or meters, depending on the current imperial/metric units setting. It is not necessary to enclose the name field in quotation marks.

The following image shows an example that will import 3 sources, as shown in a spreadsheet.

Image 1: Example of source import CSV file shown as a spreadsheet.

Saving as a CSV file produces the following as a text file.

Image 2: Example of source import CSV file saved as a text file.

Moving/line sources

A source may be stationary or moving/line. The available solvers do not calculate true line sources, instead a moving or line source is approximated by calculating the levels for a series of point sources along the desired source route. Increasing the number of intermediate points along the route increases the accuracy of the approximation, at the expense of calculation time and memory requirements.

Intended use case

Moving sources use incoherent addition of the contributions from each point along the track. This is appropriate for sources that move slowly relative to the speed of sound, such as vessels or towed arrays. It is not suitable for modelling processes that require coherent addition, such as the contributions from successive compression/dilation zones along a pile during impact piling. For peak level predictions from piling, a single stationary source with an appropriate source level is the recommended approach.

Clicking the checkbox Moving source enables the Set motion button, which shows the Set source motion form. On this form, add and remove waypoints by clicking in the Add or Remove column. Add as many waypoints as needed to define the source path.

The x, y and z columns give the location of each waypoint. The Time column contains the time taken for the source to travel from the preceding waypoint (on the row above) to the current waypoint, and the Points column contains the number of points between the waypoints where sound levels should be calculated. The position of the point at position_index (starting from 1) between the waypoints is given by

position = waypoint1 + (position_index)/(points_between_waypoints)*(waypoint2 - waypoint1)

The values in the column Time column are in arbitrary units. The total scenario period is taken as the greatest total time for any of the moving sources in the current scenario. Other moving sources in the scenario are inactive after their motion is finished. All stationary sources are taken to be active for the entire period (and then modified by the Duty % parameter).

For time domain solves, it is assumed that a single instance of the time series is short in comparison to the overall source motion, so that the source does not move while the time series is emitted.

The Time column can be switched between different units: time (seconds), speed (m/s, km/h, knots, or ft/s). Choose whichever is most convenient for your data.

For long tracks it can be useful to import waypoints from either a CSV or GPX file.

CSV-files can be delimited by either ‘TAB’, ’;’ or ’,’ and can be pasted from most spreadsheets using the common ‘Ctrl+V’ command. Headers are ignored. Also note that ‘Time’ and ‘Sections’ for the first point are ignored.

GPX-files are commonly available from tracking devices and can be imported into dBSea. dBSea currently supports tracks and routes in the GPX format. A valid UTM zone must be set in the project for GPX import, as the GPS coordinates are converted to easting/northing.

If your scenario involves a moving source always solve after changing level type!

Moving source memory options

When Retain all calculated levels is checked, dBSea stores the full sound field for every position along the track. This allows detailed time-series analysis at probes and animated export, but uses significantly more memory. When unchecked, dBSea uses a gridded transmission loss approach that is much more memory-efficient but does not support time-series analysis or animation.

Tip

Version 3.0.15 and later include improvements to memory handling that significantly reduce the impact of retaining all calculated levels. If memory is a concern, consider updating to the latest version.

View cross section

A simplified cross section for the current source can be viewed by clicking View cross section. If there are calculated sound levels, the levels along the current slice are shown. The current slice may be changed with the up/down buttons or by clicking on a direction in the compass rose. Clicking the button Show cross section button shows the chosen cross section in the main graphics area.

Source and probe array tool

The array tool (Tools → Source/Probe Array Tool) creates multiple copies of an existing source or probe in a linear arrangement. This is useful for modelling arrays of identical sources such as turbine foundations or a line of piling locations, or for placing a line of receiver probes.

Settings:

• Sources / Probes — choose whether to create sources or probes
• Copied from — select which existing source or probe to clone
• Spacing (m) — distance in metres between each element
• Direction (°) — compass bearing of the array line (0° = North, 90° = East). Click the compass widget to set the direction visually, or type a value directly. Angles snap to 15° increments when using the widget.
• Number of objects to create — how many copies to place along the line

Each new element is a full clone of the original — all properties including spectrum, directivity, and time series are inherited. The array is placed horizontally; all elements share the same depth as the original. After creation, each element is an independent object that can be edited or removed individually.

Display thresholds

In the area Display of optional thresholds for this source, it is possible to show a given threshold around the current source. Entering a threshold level in the text box or choosing one of the available thresholds from the dropdown list, and pressing the button Show threshold, enables display of the threshold. In the main graphics area, a circle around the source shows the average distance to the threshold, and a line emanating from the source shows the maximum distance and angle to the threshold.