Background

A conventional hands free kit (HFK) is effectively an earpiece and microphone electrically connected by means of wires to a mobile phone thus allowing the mobile phone to be operated at arms length from the head and thereby reducing the Radio Frequency Radiation (RFR) exposure to the head and brain. Studies have shown that the HFK wires can act as an aerial, picking up RFR from the phone itself and channelling RFR directly to the ear and brain. While the main body of expert opinion believes that HFKs significantly reduce the RFR at the head, some studies have shown a three-fold increase. This report details the protocol used to measure and compare the Specific Absorption Rate (SAR) at the head and ear resulting from RFR from mobile phone under normal use at the head, a conventional HFK with wires and a new type of HFK employing a non-metallic acoustic coupling. The SAR measurements were performed by NATA, an independent specialist laboratory accredited for RFR and SAR measurements on mobile phones. The tests were performed with "State-of-the-Art" Dosimetric Assessment System (DASY3) developed by the Swiss Federal Institute of Technology (ETH). The DASY3 is also known as the Kuster System. The work was commissioned by Safe-T-Fone Pty Ltd.

Methodology

Specific Absorption Rate is defined as the rate of absorption of Electromagnetic Energy per unit mass of biological tissue. Electromagnetic energy is absorbed by the body as a consequence of exposure to RFR. The measured SAR quantifies the energy that will be absorbed by the part of the body exposed to the RFR. A Generic Twin Phantom filled with tissue simulating liquid was used to simulate the human torso. The methodology used in this testing was generally in accordance with prEN50361, the European standard that defines the protocol for SAR measurements on mobile phones. The methodology was also equivalent to the mandatory exposure standards specified by the Australian Communications Authority for mobile and cordless phones as well as the mandatory requirements of the USA and Canada. SAR measurements were performed at the head and ear.

The mobile phone was placed in the normal user position at the head, and baseline SAR measurements were first performed at the left and right ear positions. A popular mobile phone controlled by a base station simulator was set transmit at full at 900 MHz and 1800 MHz. The second part of the testing evaluated the SAR of the conventional HFK (with wires) while the third part of the test evaluated the SAR of the Safe-T-Fone HFK (acoustic coupling without wires). The HFK was attached to the mobile phone with the HFK connecting cable taped along the length of the phone and it's antenna, represent worst case coupling of RFR to the HFK cable. The phone was placed 80cm away from the body (to simulate hand held use) and SAR measurements were then performed inside the phantom at the ear position for both types of HFK.

Results

The SAR measured at the head, due to the normal use of the popular mobile phone was in the range 1.03 to 1.13 W/kg. The worst case SAR for the conventional HFK (wires) was 0.156 W/kg while the worst-case SAR for the Safe-T-Fone HFK (acoustic coupling) was 0.0011 W/kg. The results show that the SAR at the head (and ear) was reduced by a worst-case amount of 99.9% when using the Safe-T-Fone (acoustic) HFK whereas the conventional (wires) HFK gave a worst-case reduction of 84.9%.

The SAR at the head with the HFK (wires) was 144 times greater than when Safe-T-Fone HFK (acoustic) was used. This result is to be expected since the Safe-T-Fone uses an insulating non-conductive tube, virtually eliminating the aerial effect caused by the wires of the conventional HFK.

Conclusions

Using the HFK (wires) reduced SAR at the head to 13.8% of the mobile phone SAR. (86.1% reduction)
Using the Safe-T-Fone HFK (acoustic) reduced SAR at the head of 0.097% of mobile phones SAR (99.90% reduction)
This compares with the normal background radiation levels nearby phone users
The SAR at the head with HFK (wires) was 144 times greater than when Safe-T-Fone HFK (acoustic ) was used.
Unlike HFK (wires), Safe-T-Fone HFK (acoustic) does not need to transmit or conduct electrical current or radiation from mobile phone user. It acts like an insulator between the user and the mobile phone.
The SAR at the head for Safe-T-Fone HFK (acoustic) is the same as that which would be received by a person from a mobile phone used by another person 80 cm away