Excess Noise Ratio
Excess Noise Ratio (ENR) is a way of describing the Power Spectral Density (PSD) of noise with respect to the thermal noise floor.
The noise floor power density is defined as -174 [dBm/Hz].
ENR [dB] = PSD [dBm/Hz] - -174 [dBm/Hz]
For example: when my noise source has an ENR of 44 [dB] around a certain frequency, the PSD of the noise is 44 - 174 = -130 [dBm/Hz], or -70 [dBm/MHz].