A pre-processing system of a signal of interest in an automatic speech recognition system in a vehicle, includes an acoustic sensor to sense the signal of interest, a non acoustic sensor to sense a non acoustic noise signal, a pre-processing unit of the signal of interest, comprising a processing section of coherent frequency bands signals for suppressing the noise from the received signal, a processing section of non coherent frequency bands signals, comprising transfer function estimation device of a signal through the vehicle cabin, and a methods selection section for determining the coherence properties of the received signal, and for selecting the processing section of coherent frequency bands signals or the processing section of non coherent frequency bands signals depending on the result of the properties of the received signal.