In a thread on the Reaper's forum some one posted this link which looks very interesting
Room EQ Wizard is a Java application for measuring room responses and correcting modal resonances. It includes tools for generating test signals; measuring SPL; measuring frequency and impulse responses; generating spectral decay plots, waterfalls and energy-time curves; generating real time analyzer (RTA) plots; calculating reverberation times; displaying equaliser responses and automatically adjusting the settings of parametric equalisers to counter the effects of room modes.
Cheers
Raul