macOS Maintaining Volume Level on Auto Restart

Hi. I have four mac minis in kiosks around Miami. They're set to restart automatically after a power failure. I've noticed, however, that when they restart in such a situation, the volume in the System Preferences is lower than what I'd set it at previously.

I guess there's some sort of volume level it defaults to. Does anyone have any ideas on how to change that?

Thanks!

Yep, I think that's what I'm looking for.

Is that an applescript, or does it go into the terminal?

I'm a complete novice with this stuff, though I've had some recent success w/ automator and applescript.

Thanks.