The calculation
of the D11C1 allows
the assessment of
the anthropogenic
impulsive sound
in water.

The Commission Decision (EU) 2017/848 define the criterion D11C1-Anthropogenic impulsive sound in water as:

The spatial distribution, temporal extent, and levels of anthropogenic impulsive sound sources do not exceed levels that adversely affect populations of marine animals.

And set the following units of measurement for the criteria:

Number of days per quarter (or per month if appropriate) with impulsive sound sources; proportion (percentage) of unit areas or extent in square kilometres (km2) of assessment area with impulsive sound sources per year.
This portal provides a tool for the calculation of the spatial distribution and the temporal extent of D11C1. Visit the section “Map” and play!