Probes

Probes are used to gain more control over the display of predicted sound levels and can be thought of as hydrophones. Sound levels are calculated throughout the project area, but to see the spectrum and level at a specific point, a probe can be placed there. A scenario can contain multiple probes, and at least one probe must always be present.

Probes can be moved by entering x and y values in the fields or by clicking and dragging in the main graphic window. The z coordinate is connected to the current vertical levels display method (Preferences → Graphics → Levels Display).

• When this is set to Max from all layers projected to surface, the level shown is the maximum from all vertical layers at that x and y location.
• When this is set to Single layer, the level shown corresponds to the specified z coordinate.

These controls can also be accessed directly from the Probes page by clicking the Show depth controls button.

Probes can be added and removed using the Add probe and Remove probe buttons. The current probe is selected using the dropdown box. To create multiple probes in a linear arrangement, use the array tool (Tools → Source/Probe Array Tool).

Spectrum Display

The chart displays the spectrum at the current probe location as a bar chart across frequency bands. If a weighting curve is selected, two sets of bars are shown — unweighted (dark blue) and weighted (light blue) — with the weighting curve overlaid as a line. The weighting selector on the Probes page is synchronised with the Marine Species Weightings frame.

The results table below the chart shows per-band levels, weighting values, and weighted levels, along with broadband totals.

Levels vs Depth

The Levels vs depth tab shows how sound level varies with depth at the probe location, from the surface down to the seabed. If a weighting is applied, both unweighted and weighted profiles are shown. Use the Levels to clipboard button to export the depth profile.

Levels vs Time

The Levels vs time tab is available for scenarios with moving sources where results have been saved for all source positions. It shows how sound levels at the probe location change over time as the source moves. Both unweighted and weighted broadband levels are plotted if a weighting is applied.

Use the Levels to clipboard button to export the time series, which includes the full spectrum at each time step.

Note

Time series are currently supported for single moving source scenarios.

Exporting Data

• Table to clipboard — copies the current probe’s results table (position, per-band levels, weighted levels) as tab-delimited text suitable for pasting into a spreadsheet.
• All probes to clipboard — exports data for all enabled probes as CSV, including probe name, coordinates, broadband level, per-band levels, and weighted levels.

Source Back-Calculation

The back-calculation tool calibrates a source spectrum based on measured data at a probe location. When field measurements at a monitoring point differ from model predictions, this tool determines what source level adjustment would reconcile the difference.

Workflow:

1. Place a probe at the measurement location and solve the model
2. Click Source back-calculation and select the source
3. Enter or paste measured levels from field data
4. Review the per-band comparison and updated source levels
5. Click Update source levels to apply the adjustment

The dialog shows a table with one row per frequency band and five columns:

Column	Description
Predicted level	Model’s predicted level at the probe (read-only)
Measured level	Your field measurements (editable)
Difference	Measured minus predicted (auto-calculated)
Current source level	The source’s existing spectrum (read-only)
Updated source level	Current source level plus the difference (auto-calculated)

Measured levels can be typed directly into the table or pasted from a spreadsheet using the Paste levels button. Pasted data should be tab-delimited with one value per frequency band. The difference and updated columns update in real time as you enter data.

After clicking Update source levels, the model recalculates and the table refreshes with new predicted levels, so you can immediately see any remaining discrepancy.

Caution

Back-calculation is designed for single-source scenarios. A warning is shown when multiple sources are present, as the method cannot attribute received levels to individual sources. It is not available for moving sources.

Level Limits and Exclusion Zones

The Level Limits dialog (accessible from the toolbar or results display) controls the colour scale range for level visualisation. It includes:

• Level range — set the minimum and maximum display levels and the colour band spacing (1, 3, 5, 10, or 20 dB)
• Histogram — shows the distribution of levels across the receiver area, helping you choose appropriate display limits
• Exclusion zone — enable a threshold level above which an exclusion zone is drawn on the map. Predefined regulatory thresholds (e.g. NOAA marine mammal criteria) can be selected from the database, or a custom level can be entered

Distance Display

The Distances to sources button shows the distance from the current probe to each source, including horizontal (xy) distance, full 3D (xyz) distance, and compass bearing.