Circuit noise voltage measured with a psophometer that includes a CCIF-1951 weighting network. Note 1: "Psophometric voltage" should not be confused with "psophometric emf," i.e., the emf in a generator or line with 600 internal resistance. For practical purposes, the psophometric emf is twice the corresponding psophometric voltage. Note 2: Psophometric voltage readings, V, in millivolts, are commonly converted to dBm (psoph) by dBm (psoph) = 20 log10V - 57. 78.