This paper deals with the analysis of auditory evoked potentials recorded in presence of radiofrequency fields emitted by a mobile phone. During measurements, spurious frequencies appear on the one hand at 50, 100, 150 Hz but and on the other hand around 83.3, 133.4 and 216.7 Hz. The first ones are due to the mains and that at 216.7 Hz comes from the GSM modulation. We show that the two others (83.3 and 133.4 Hz) are related to the 216.7 Hz component and to the sampling frequency. In order to get rid of these parasitic components, a low-pass filtering is applied before further analysis. A study of the acquisition system behavior in the band [0; 40 Hz] is carried out to conclude on the validity of this analysis.