A conversation with a friend made me suddenly recall that when I was a kid in the early 80’s, we could occasionally hear a faint rendition of the major local AM station coming from the faucet of the kitchen sink. We lived just a mile or two from the broadcast antenna.
It was very faint and had a spooky sizzling quality, but it was unmistakable. Our wall-mounted telephone also picked it up, but more distinctly. I can understand the telephone noise reason, as there’s an amplifier and speaker. But a faucet? How?
In: Physics
Your faucet is attached to a pipe, likely made of copper. That long copper pipe is basically an antenna capable of picking up strong radio waves. A strong enough signal can induce small vibrations in the pipe, which are then amplified by the bowl shape of the sink.
The broadcast tower is pumping out a huge amount of energy, likely 50kW in your case. Because it’s AM you don’t need complicated circuitry to demodulate it, just something that vibrates based on how much electricity is flowing through it.
A 50kW speaker would be quite loud at the same distance, it’s only faint because the sink and pipes it’s connected to make a poor radio receiver.
If you’ve heard of crystal radios, those are powered by the radio waves, and work at much longer distance.
Metal in the pipes was acting as an antenna. It’s important to remember that radio signals and such are just waves producing the programming you hear. Very few of them are directed (especially in broadcasting, you want it to reach your whole market area) so they radiate outwards from the broadcast antenna and get picked up by anything that can receive it. So interestingly enough, the pipes did it.
If you put another broadcast antenna equidistant in the opposite direction and had it broadcast something, you’d probably hear both in the sink and it would seem garbled.
That’s the gist, I don’t mess around a lot with AM radio but from what I remember it’s the most “primitive” of broadcast technology and is on it’s way out besides localized broadcasts for stuff like weather. Somebody who deals more with radio’s will answer shortly I’m sure.
This used to happen to me and my wife in our first house. It was very close to a massive AM radio tower in SW Ohio and we could faintly hear voices all around the house, especially in the kitchen at night. It scared the shit out of her and took us years to figure out.
Sometimes in the old days you’d hear about people detecting radio from the fillings in their teeth.
AM is produced by mixing a carrier signal (frequency of the radio station) and a modulating signal (audio) through a non-linear conductive element i.e. element in which the relation between voltage and current are not linear. A diode is the more commonly known non-linear element, which is often the element used to illustrate an AM modulator or demodulator in electronic drawings.
To demodulate, you do the reverse operation, so you feed your AM signal through a non-linear element which output your carrier and audio signal (and other components).
Your sink is a non-linear element.
It demodulates the AM signal which produces the audio signal, which is probably translated to sound through vibration since it’s wall is quite thin.
Ok, the “copper pipes” as antenna makes sense to me, but what’s converting EM waves to physical vibrations? Slight magnetism in something? Mineral-rich water droplets?
In the 70s and 80s my family used to live in a house that was three blocks from a 50,000 watt AM radio tower. Used to pick up the broadcast on our phones and if anyone still has a landline there now they still can. Don’t remember hearing it from the plumbing.
Run your fingers down the teeth of a comb. Or at least imagine it for now, you know that sound it makes? Now run your fingers down it faster. It seems ike the pitch changes doesn’t it? Like it’s higher pitched? It’s an illusion.
The carrier wave of an AM signal stays at the same pitch much like the teeth of the comb. If you could directly hook an AM signal to a speaker you would hear a similar illusion.
Since you can hear that illusion, you could hear the actual transmission if only you had something to turn the electromagnetic waves in to oscillating air pressure (that’s what sound is).
Your sink was behaving as the speaker.
I believe there are 3 things you were missing when you asked this question:
1: Yes, if you could hear an AM signal it could resemble something like the source without being decoded. There is still one step between the source sound and carrier wave though, so it doesn’t sound great without being “decoded.”
2: All you need to do to turn an electromagnetic wave into physical sound is make a thing that vibrates in response to to the electromagnetic waves. Usually a magnet with the signal pushes and pulls a diaphragm that moves air – thats the big round thing on a speaker. It doesn’t *need* to be purpose built for sound though. Ever hear the hum of an electeical transformer? You can hear the AC power bevause the casing of the transformer is behaving just like your sink. Its a big metal thing that is “playing the sound of the electrical grid” (and our power grid is just a super low frequency electromagnetic wave).
3: AM stands for “amplitude modulation” – this could be restated as “we change (modulate) how loud (amplitude) the signal is really fast.” As a consequence of this, to be able to actually use AM we need the signal to be stronger, or “louder” if you will. Long story short, this is why you don’t *need* an amplifier to get somethig audible to the human ear. The signal is enough to power a small speaker.
Remember how I said our power grid is just low frequency electromagnetic waves? Well radio is then just high frequency wireless power.
There are other nuances to all of this – electromagnetism isn’t something you can really intuitively grasp in one sitting without visual aids.
I swear this story ends up being related to the question…
John R. Brinkley was a quack doctor (or at least a quack who falsely claimed to be a doctor) who made a lot of money in the early 20th century by surgically installing goat testicles in humans. He believed that the always-virile goat would imbue human men with its energy and cure all their medical woes.
It should go without saying that this didn’t work. Optimistically, if this kind of thing is done with best practice and sterile instruments, your body will recognise foreign tissue and break it down. Perhaps unsurprisingly, Brinkley was not using sterile instruments and best practice. People got infected and died, and Brinkley was ultimately forced to flee to Mexico.
Unrepentant, he set up a radio station just inside the Mexican border, where he would broadcast country music and ads for his various medical supplements and goat ball treatments. He was actually a major reason for country music becoming popular in the American Southwest. Determined to reach as many people as he could with his broadcasts, and unconstrained due to Mexico’s lack of broadcasting laws, Brinkley built a transmitter that was basically a doomsday weapon.
The transmitter that Brinkley created was so powerful that you could pick up his radio show as far away as Canada. More locally, birds that flew in front of the transmitter would explode in flight. The signal was so strong that any metal object would pick up Brinkley’s station. Field workers could hold up a shovel and hear it. Barbed wire fences would pick it up. Anyone living locally who was unfortunate enough to have metal fillings would be able to hear Brinkley’s broadcasts INSIDE THEIR OWN HEADS, also giving rise to the “crazy people can hear broadcasts on their fillings” joke. Turns out this is actually true under some circumstances.
Eventually the authorities stepped in and made Brinkley dismantle his giant radio tower. Anyway, the lesson is that any metal object can pick up a radio signal, and if you’re a crazy fake doctor with a million watt transmitter, ALL metal obejects will pick it up.
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