On a recent measurement session taht involved salt water, it was decided to use a Rational Acoustic RTA-420 mic instead of the more expensive DPA4007. Rational Acoustics sells a verion of the RTA-420 mic that comes with a calibration file to load into Smaart. Once done, an RTA-420 provides results as if the mic were perfectly flat.

The RTA-420 mic we had didn’t include a calibration file. How would we calibrate the mic against the DPA4007?

This Rational Acoustics forum thread explains how:

Rational Acoustics forum – Make your own microphone calibration curves in Smaart 7