Frequency Response graph

The Frequency Response graph is context sensitive to input data from the active echogram. The graph displays the NASC of a selection/region for a set of Sv variables that have been recorded in parallel on differing frequencies.

NASC is normalized against a reference value (the reference value is the NASC at one of the displayed frequencies).

To display the Frequency Response graph from an Sv echogram:

  1. On the View menu, point to Graph, then click Frequency Response.
  2. The Frequency Response graph properties dialog box will allow you to configure the graph, and select displayed variables and the reference variable.
  3. Make a selection, or click on a region (on an echogram you selected in step 2).
  4. Use Graph menu > Linking to select the linking to the graph.


  • It is only possible to view one of this type of Frequency Response graph per EV file.
  • Listed Sv variables have a frequency that is either read from file or in the ECS file. Sv variables with a default frequency won't appear in the Sv variables list. Such Sv variables arise from file formats that do not contain frequency information.


Korneliussen, R. and Ona, E (2003). Synthetic echograms generated from relative frequency response. ICES Journal of Marine Science, 60:636-640.

See also

About graphs
About Linking Graphs
Frequency Response graph properties dialog box
Relative Mean dB graph