The output voltage of a microphone when it is not connected to a load, or, when the load is about twenty times the impedance of the microphone itself.
"I am very pleased with the overall results of all three transfers. The "Hall of Presidents" and "Country Bear Jamboree" transfers were outstanding, with almost no hiss or pop. The "Tiki Room/Jungle Cruise" soundtrack had some minor hissing in the first couple of tracks, but side 2 was superlative. Given that that album was over thirty years ..."