In order to enable better estimation of dynamic interference noise, a device and a method for estimating interference noise provide a value for the power density of a total signal, containing a wanted signal and the interference noise to be estimated, in a current time window. The value of the total signal is compared with an estimated value, multiplied with an amplification factor, of interference noise from a time window prior to the current time window and the smaller of the two values from the comparison is used as a preliminary estimated value for the interference noise in the current time window. A codebook estimated value for the interference noise in the current time window is also provided. Finally, the larger of the preliminary estimated value and the codebook estimated value is used as the estimated value for the interference noise in the current time window.