A common problem in the world's most widespread cellular telephone system, the GSM system, is the interfering signal generated in TDMA cellular telephony. The infamous "bumblebee" is generated by the switching nature of TDMA cellular telephony, the radio circuits are switched on and off at a rate of approximately 217 Hz (GSM). This paper describes a study of two solutions for eliminating the humming noise with IIR notch filters. The simpler one is suitable for any exterior equipment. This method still suffers from a small residual of the noise, resulting from the IDLE slots of the sending mobile. The more advanced IIR structure for use within the mobile also eliminates this residual.