Hi gweadock,
Might be a late response, but I was looking for this exact answer and found your reply.
But there is another simple option which I stumbled on.
If you right click on the microphone level slider in windows sound control panel for your USB microphone, you will get two options:
percentage or decibels
Select decibels and it'll be exactly what you want.
My zoom H1 USB microphone was +0.1dB at 54 percent level.
I found different devices can have a different 0dB point so check yours.
Good luck.
Might be a late response, but I was looking for this exact answer and found your reply.
But there is another simple option which I stumbled on.
If you right click on the microphone level slider in windows sound control panel for your USB microphone, you will get two options:
percentage or decibels
Select decibels and it'll be exactly what you want.
My zoom H1 USB microphone was +0.1dB at 54 percent level.
I found different devices can have a different 0dB point so check yours.
Good luck.