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 while in bird’s eye view mode (press the Reset View button to return to this 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 metres, 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.

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 (s) column contains the time in seconds taken for the source to travel from the preceding waypoint (on the row above) to the current waypoint, and the Sections column contains the number of sections between the waypoints, each ending in a point where sound levels are calculated. The position of the point at position_index (starting from 1) between the waypoints is given by

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

Each calculation point contributes for the time the source spends there (the segment time divided by its number of sections, with points on a waypoint averaged between the adjoining segments), so the energy along the track does not depend on how finely it is divided. The total scenario period is taken as the greatest total time for any of the moving sources in the current scenario, and each point’s contribution to time-averaged levels is scaled by its dwell time relative to that period. 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 (s) column can be switched to speed with the Set speed options (m/s or ft/s, km/h or mph, and knots, depending on the unit preference). Speeds are converted to segment times using the segment length. 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.

Re-solve after changing the level type to or from Max sound pressure level, or between any of the time-series level types. Switching between Sound pressure level and Sound exposure level is a display conversion and needs no re-solve, also for moving sources.

Moving source memory options

When Moving sources retain all calculated levels (memory intensive) 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.

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 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.