FM improvement threshold

In telecommunication, FM improvement threshold is the point in an FM (frequency modulation) receiver at which the peaks in the RF signal equal the peaks of the thermal noise generated in the receiver. A baseband signal-to-noise ratio of about 30dB is typical at the improvement threshold, and this ratio improves 1dB for each decibel of increase in the signal above the threshold.

Source: from Federal Standard 1037C and from MIL-STD-188