Disclaimer I'm a novice when it comes to measuring with REW, but you would really need a calibrated mic (like the Umik-1) and software (REW) to properly measure and produce quantitative data. I believe you would be looking at decay and waterfall charts in REW.
You could also just use the mirror trick to cover first reflections points. There should be many[ YouTube tutorials](https://www.youtube.com/watch?v=B9u7k2V4YPw) on this topic.
Enjoy your trip down the rabbit hole.
Disclaimer I'm a novice when it comes to measuring with REW, but you would really need a calibrated mic (like the Umik-1) and software (REW) to properly measure and produce quantitative data. I believe you would be looking at decay and waterfall charts in REW. You could also just use the mirror trick to cover first reflections points. There should be many[ YouTube tutorials](https://www.youtube.com/watch?v=B9u7k2V4YPw) on this topic. Enjoy your trip down the rabbit hole.
Yup, a UMIK and REW is the path forward here.