1. A method of estimating noise level in data including voice information and noise, the method comprising: receiving the data as a sequence of input values, the data provided in a frequency domain signal comprising frequency bands; adding a bias value to at least two of the input values of the sequence, the bias values based, at least in part, on a corresponding frequency band; transforming the data provided in the frequency domain signal comprising frequency bands by applying a first non linear mapping to the input values and the corresponding bias values, a derivative function of the first non linear mapping decreasing in magnitude as the input values increase in magnitude; smoothing the transformed data, the smoothing being performed by a filter block comprising two inputs, one of the two inputs receiving the transformed data and another of the two inputs receiving speech indicator data from a speech detector; transforming the smoothed transformed data by applying a second non linear mapping to the smoothed transformed data and the corresponding bias values, the second non linear mapping being opposite to the first non linear mapping; determining an estimate of the noise level in the data based, at least in part, on the transforming the smoothed transformed data; and using the determined estimate of the noise level in the data to produce a noise corrected signal.