The minimum/maximum frequency range should almost always be set to the range of your input PSD curve. If it is not, the RMS of the input to the structure will not be the same as that specified by the input curve. This will also effect the RMS results calculated.
In most cases the frequency steps should be defined using the ‘automatic’ method. You may want to manually set the frequency steps if the input PSD curve is not smooth but has a lot of significant jagged step changes in amplitude. For these cases put a master interval at each frequency where you have a step change in the input. You may also need to manually set the frequency steps if you need uniform equal frequency step results to use as input into some other program.
