This study was carried out as part of the European "Guard" project that addressed the potential effects of cell phones on the hearing system. A sample of 169 young adults with no hearing problems took part. Auditory function was assessed immediately before and after exposure to EMFs, and only the exposed ear was tested. The procedure was conducted twice in a double-blinded design, once with a genuine EMF exposure and once with a sham. These were done at least 24 hours apart. Half of the participants received GSM at 900 MHz (full power 2W, SAR approximately 0.41 W/kg), and half at 1800 MHz (full power 1W, SAR approximately 0.19 W/kg). The exposure consisted of speech at a typical conversational level via an earphone, and was at full power for 10 minutes. Tests for assessment of auditory function were hearing threshold level (HTL), transient otoacoustic emissions (TEOAE), distortion product otoacoustic emissions (DPOAE), and auditory brain stem response (ABR).

Analysis of the data showed there were no effects of the exposure to GSM signals on the main measures of the status of the auditory system.