Source Directivity
Source directivity allows you to model sources that radiate sound non-uniformly, with different levels in different directions. This is common for many real-world sources such as ships, pile drivers, and acoustic devices.
Solver Support
Section titled “Solver Support”Directivity is supported by all PE and Ray solvers (both 3D and 2D). The simple geometric spreading solvers (10 log, 20 log) do not support directivity.
Setting Directivity
Section titled “Setting Directivity”The source directivity is set per frequency on the Directivity form. You can:
- Enter values directly in the table
- Import from a text file containing one value per line
To import a text file for a specific frequency, click on the File cell at the top of that frequency’s column.
Angle Convention
Section titled “Angle Convention”- +90° - Vertically down (toward the seafloor)
- 0° - Horizontal from the source
- -90° - Vertically up (toward the surface)
Directivity values are linearly interpolated between the angles you specify.
Display Notes
Section titled “Display Notes”Greyed-out rows indicate angles outside the current range of takeoff angles configured for the ray solver. These angles will not contribute to the calculation.
Practical Considerations
Section titled “Practical Considerations”- For omnidirectional sources, leave the directivity at 0 dB for all angles (the default)
- Directivity patterns are typically frequency-dependent—higher frequencies often show more directional behavior
- If you have measured or manufacturer-supplied directivity data, import it at the corresponding frequencies
- For frequencies without directivity data, dBSea interpolates between the nearest frequencies with data