[Tobiah]

Make a "dummy mic" by connecting a 150 ohm resistor between pins 2 and 3
of an XLR plug. Plug it into the interface, turn the gain up full, and
record the noise. You don't actually need to record, just read the
record level on the meter of your DAW program.

I'm going to go get the resistor today. Cursory search
says that metal film are the best for low noise applications.
Anyone agree?