How to calculate Loudness/Sone (ISO 532B / DIN 45631)?

In Plot->PlotType/Routing/Test..., select Frequency Response/Spectrum as plot type as shown in the figure below.

Click the  button to exit the dialog box.

Now go to Plot->Plot Type Settings->Active Plot... to display the dialog shown below.

First select the horizontal axis as shown below

Then make sure that you select specific loudness as shown above. You have two choices of loudness. If you are measuring under free field conditions, select Spec. Loudness (free).

For example according to EPLF NORM 021029-1 the measurements should be done under free field conditions. A free field condition is defined as:

•      A laboratory room which provides a free field over a reflecting plane as in a semi-anechoic room.

•      A room in which the contribution of the reverberant field to the sound pressures in the measurement positions are small compared with those of the direct field of the source.

In a diffuse field, the reverberant field contributes to the direct field of the source, which it will do in an ordinary room. If this is the case, select Spec. Loudness (diffuse).