On the Effectiveness of Aluminium Foil Helmets: An Empirical Study Ali Rahimi1, Ben Recht 2, Jason Taylor 2, Noah Vawter 2

17 Feb 2005

1: Electrical Engineering and Computer Science department, MIT.

2: Media Laboratory, MIT.

Abstract

Introduction

We describe our experimental setup, report our results, and conclude with a few design guidelines for constructing more effective helmets.

Experimental Setup

The three helmet types tested The Classical The Fez The Centurion

We evaluated the performance of three different helmet designs, commonly referred to as the Classical, the Fez, and the Centurion. These designs are portrayed in Figure 1. The helmets were made of Reynolds aluminium foil. As per best practices, all three designs were constructed with the double layering technique described elsewhere [2].

A radio-frequency test signal sweeping the ranges from 10 Khz to 3 Ghz was generated using an omnidirectional antenna attached to the Agilent 8714ET's signal generator.

The experimental apparatus, including a data recording laptop, a $250,000 network analyser, and antennae.

A network analyser (Agilent 8714ET) and a directional antenna measured and plotted the signals. See Figure 2.

Because of the cost of the equipment (about $250,000), and the limited time for which we had access to these devices, the subjects and experimenters performed a few dry runs before the actual experiment (see Figure 3).

Test subjects during a dry run.

The receiver antenna was placed at various places on the cranium of 4 different subjects: the frontal, occipital and parietal lobes. Once with the helmet off and once with the helmet on. The network analyzer plotted the attenuation betwen the signals in these two settings at different frequencies, from 10Khz to 3 Ghz. Figure 4 shows a typical plot of the attenuation at different frequencies.

A typical attenuation trace form the network analyser

Results

Conclusion

It requires no stretch of the imagination to conclude that the current helmet craze is likely to have been propagated by the Government, possibly with the involvement of the FCC. We hope this report will encourage the paranoid community to develop improved helmet designs to avoid falling prey to these shortcomings.

Acknowledgments

There's also an informative video (youtube version) courtesy of Discovery Channel's Daily Planet.