I live in the attic of a building on 14th Avenue East and Denny Way, which means I am at the peak of Capitol Hill. Often, my stereo receiver will pick up radio signals. The noise overwhelms my regular music, and I can't use my personal recording equipment without it being tainted by radio waves, which totally sucks because I am anxious to record my music. I have a hunch the noise comes from the huge towers on 17th Avenue and Pine Street. Why is this happening, and more importantly, how can I make the noise stop?
Beamed Into My Head
The towers at 17th and Pine are a good hunch. Hug the next electrophysiologist, neurologist, or physicist you meet; the solution they use should also work for you.
Let's talk about radio for a moment. Any changing electrical field creates a magnetic field. This magnetic field can then spread out, as a wave. When this electromagnetic wave hits any conductor—an antenna, a metal fence, or your microphone wire—the magnetic field gets converted back into a current. If it happens in rabbit ears attached to a television, something good and wondrous has happened and you can watch TV. If it happens in the wires in your attic, you start hearing voices. Bummer.
Imagine you're living at the end of the 19th century, when all of this was worked out in Scotland, Italy, and New York. "With electricity we can make these waves, invisible waves, that pass through everything, including you. Then way over here, we can turn these waves, that travel somehow right through walls, back into electricity." You'd probably ask for a drink, or a pitchfork. People still don't feel quite right about all this, as evidenced by the whining by some living under high-voltage power lines. If radio were invented today, San Francisco would probably ban it.
Today, we live in a world bathed in radio waves—waves we didn't ask for, that are constantly passing through everything. Your attic, at the top of a hill and right next to transmission towers, is particularly susceptible. What can we do?
Shielding! When the electromagnetic wave hits something metal, the creation of the current uses up the wave. So, if we put what you want kept free of radio waves inside a metal box, disco! (Yes, aluminum-foil hats do work. Well, sort of. The neck gets in the way.) In fact, it doesn't even need to be a solid metal barrier. A wire mesh will absorb all waves of a wavelength longer than the openings in the mesh. As a bonus, such a mesh cage—deemed a Faraday cage, after British chemist Michael Faraday—will also allow you to breathe. A Faraday cage keeps your microwave from killing you and it can keep your recordings free from interference.
Send your science questions to firstname.lastname@example.org.