In impulsive noise, the inputs of the belief propagation decoder can be complex to compute or even impossible when the noise distribution is not known. We propose a simple approximation of the log-likelihood ratio that maps the channel output to the input of the error correcting decoder, for instance, LDPC decoders. This approximation is designed for additive impulsive noise channels, nevertheless, it is not computationally demanding and easy to be implemented. It requires the estimation of three parameters and we propose an efficient way to do it. Moreover, in terms of performance, our solution is barely discernible from the optimal receiver which is computationally prohibitive.