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

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

The source directivity is set per frequency on the Directivity form as an attenuation in dB relative to the source level: positive values reduce the level in that direction, and 0 dB leaves it unchanged. The pattern depends on the vertical (declination) angle only and is the same in every horizontal direction. 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

+90° - Vertically down (toward the seafloor)
0° - Horizontal from the source
-90° - Vertically up (toward the surface)

The angles form a uniform grid from −90° to +90° (set by Number of angles), and directivity values are linearly interpolated in dB between them.

Display Notes

A warning is shown when angles lie outside the initial angle range configured for the ray tracer; those angles do not contribute to a ray solve.

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 behaviour
If you have measured or manufacturer-supplied directivity data, import it at the corresponding frequencies
Directivity is applied only at the frequencies for which a pattern is entered. The ray tracer requires an exact frequency match; the PE solver also accepts the nearest pattern within 10% of the solve frequency. Bands without a pattern are treated as omnidirectional, so enter a pattern for every band that matters