I've got both. I just don't have a calibrated mic for my USB preamp. I can use the SPL meter to eyeball calibrate the computer I suppose. It won't be exact, but for our needs it should be fine. I'll look into this - sounds like a good winter project. I should be able to produce waterfall plots of volume at frequency. That would be a good descriptor of whether it's a thud or a smack sound.
Will doing it indoors cause any problems with sound reflections?