Extreme Newbie questions, for capturing non-music sounds

[danclarkwcp]

I'm almost embarrassed to ask these questions, but I've read through the manual a couple times, and can't figure out what to do. Although I'm a professional photographer, audio is not my thing (obviously). Basically, I want to capture the sound of a ball hitting a surface, and measure both SPL and frequency of the impact. I have a UMM-6 microphone, which is connected to an iMac Pro via one of the USB ports, running Mac OS Sonoma 14.5. I've downloaded the calibration file from Dayton Audio for this exact microphone (using the mic's serial number), and I understand the cal file includes the sensitivity figure which REW needs to read the input volume setting to correctly show SPL. I've gone to my Mac's System Settings, first to Audio MIDI Setup, to make sure it's using the correct settings (Format 48,000 Hz, Primary Stream/Primary is set to Value 0.103, dB 0.0), and Privacy & Security>Microphone to ensure REW is toggled on.

Now I'm in the REW Preferences, on the Soundcard pane. Sample rate in 48kHz, Input device is UMM-6, but I can't figure out what to use for Output device. Or does this not matter? And then, what else do I need to set up on the Soundcard pane, or any other tabs, to begin recording? Do I need to calibrate the soundcard? Again, all I want to do is see the dB and peak frequency of the sound of different balls hitting a surface.

If there is somewhere in the manual that covers what I'm trying to do, you can just point me in that direction. I don't mind reading, and re-reading, until I understand what I need to do.

Thanks in advance,
Dan