An N-element noise model of a receiver is created, with the number of noise elements (N) determined by the equation N=(number of variable gain components+1). The components in the model are grouped into domains with each noise element associated with a domain. The domains are defined so that the noise contributions of the components within each domain are independent of the receiver gain state. A noise value is computed for each noise element. Each noise value is determined with reference to a particular point in the model, and is computed in a reference state. Input-referred noise values are calculated using each noise value and the current gain state data for the receiver. A composite input-referred noise value is computed using the input-referred noise values and subtracted from a measurement signal to reduce noise in the signal. The composite noise value can automatically be re-calculated for any receiver gain state.