Psophometric voltage

Psophometric voltage is a circuit noise voltage measured with a psophometer that includes a CCIF-1951 weighting network. 
"Psophometric voltage" should not be confused with ""psophometric emf," i.e.", the emf in a generator or line with 600 Ω internal resistance. For practical purposes, the psophometric emf is twice the corresponding psophometric voltage. 
Psophometric voltage readings, "V", in millivolts, are commonly converted to dBm(psoph) by dBm(psoph) = 20 log10"V" – 57.78.