Safe and Sound - Cell Phone Shield Test - blog 19

The deadline for this challenge has been extended again, so I can squeeze in a few more blogs. Perhaps some real applications of all this instrumentation I have put together.

This blog shows some quick tests I did to see if shielding makes a difference to cell phone radiation. These tests are a follow up to an earlier blog on microwave radiation.

To set up for the test, I made a shield from two 3D printed shells sandwiching a layer of aluminum foil between them.

The shell and foil covered 5 of the 6 sides of the phone - about 1mm from the back of the phone and about 2mm from the sides.

I ran some tests with and without the shield to see if it made a difference - and it definitely did. I was a bit surprised by the results.

The main scenario that I am interested in is the case where the phone is in a pants pocket as studies show this results in lower testosterone and lower sperm count. So I placed the phone and meter in appropriate locations on a Hybrid III crash test dummy and took some readings. These particular dummies have seen some major trauma (explosions) and you can see they look a bit charred, but the geometry is still good - this is a 50th percentile male.

These readings are the maximums I saw in this geometry. The shielded maximum was a rare spike, it spent most of its communication time at about 1 mW/m².

The unshielded maximum is closer to its normal value ~ 150 mW/m².

In this experiment the shielded case yielded 10 to 100 times less radiation density at the location of interest.

This is not a particularly scientific experiment, but the results do suggest it might be worth investigating shielding in a more scientific way.

I did not check to see how cell phone performance was impacted by the shield - I imagine the shield didn't help communications ...

To get a bit more of a feel for what the readings look like in real time, I made a video of typical readings. Viewers can decide if the readings are meaningful for themselves.

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The other geometry of interest is holding the phone at your ear.

Here are some images showing a reading with the meter where an ear might be and what happens if a metal plate is inserted between the phone and the meter.

Note the units change in these images - one is mW the other is uW, so the last image is 4.6 mW/m²

One observation is that the field strength seems to be lower at the face of the phone compared to the sides - by about 50%.

The other observation is that the metal plate cuts the field strength by more than a factor of 100. Again, I did not determine how this plate impacts cell phone communications performance.

These experiments are not trying to determine what level of radiation is safe, just trying to get a feel for whether partial shielding can reduce radiation exposure.

All links to blogs related to this project can be found in the first blog here:

Safe and Sound - Invisible Hazardous Environmental Factors Monitoring System - blog 1