Participants were instructed to sit and look at a white screen. Since the laboratory was an extremely quiet environment (purpose-built for sleep studies), a white noisesignal was created by turning on the TV receiver tuned to an unused channel in order to mask any residual sound from the handset.
A modified digitalmobile phone transmitting in 'test mode' was controlled by a laptopcomputer via a data cable, which was disconnected after the output was set. The mobile phone was attached to a plastic arm mounted on a modified non-metallic welding helmet, and it rested against the subject's right cheek. The phone's loudspeaker circuit was disabled, and wads of plastic foam were placed in the pouch to absorb and eliminate aural cues from the buzzing of circuitry.
Volunteers were actively or sham exposed in a double-blind cross-over design in random order on successive Sunday nights, immediately prior to retiring to bed, and also prior to the attachment of recording electrodes and other sensors.
The power output of the phone was checked by an independent person using a test antenna connected to a power meter before handing it over to the experimenter, who was thus blind to the status of the phone. Phone outputs were also checked by an independent laboratory three times during the project. In addition, Specific Absorption Rate (SAR) measurements were conducted inside a Specific Anthropomorphic Mannequin (SAM) phantom using a precision robot RFDosimetric Assessment System (DASY4).