Wow. I had no idea this could happen!

(Rest of this post is by Michael Albaugh, except for the parts that quote me.)

From: Michael Albaugh
Subject: Re: Wait, what?  Can speakers pick up radio by themselves?
To: Karl Fogel
Cc: The Usual Suspects
Date: Fri, 11 Dec 2015 10:03:22 -0800

Disclaimer: It has been quite a while since I had to deal with this stuff for pay, and my amateur license expired so long ago they recycled my call.

On Dec 11, 2015, at 9:13 AM, Karl Fogel wrote:

This is happening, this is literally happening right now:

I have plugged my phone headset (which double as my desk headphones) into my computer speakers. This a standard pair of small standalone computer speakers, one of which plugs into the computer’s sound port with a standard 2.5mm connector, and the other speaker connected to the first. The first speaker also has a headset jack and a volume control on the front.

It presumably also has a power supply. That is, these are amplified speakers.

With my headset plugged into that speaker’s jack, and the speaker volume turned all the way down, I can hear a radio station playing in the headset, faintly and with some staticy fuzz, but clearly. I don’t know which station it is, but sometimes the pop music stops and an announcer comes on (I can’t quite hear what he is saying, though I might be able to catch it next time he comes on).

This is not surprising. What you have is some consumer-grade cables (i.e. not particularly designed to reduce the reception of stray signals at all cost, or any cost) plugged into a device with some non-linear components (inherently, such as transistor and diodes, or unintentionally, such as inductors with other than air cores) and including a means to amplify the result. That is, you have a crystal radio hiding in your amplifier.

See also “Why do I get the local radio station on my fillings?”

However, if I turn the volume knob on the speaker up at all, then the station fades out and I get silence.

Or, you have shifted the sum of the intended input and the signal that being “detected” out of the range of the non-linearity.

If I unplug the speakers from the computer, then I don’t hear the station anymore.

Here I am leaning more on speculation, but perhaps the speakers are sensing the (lack of) DC bias on their input and shutting down the output.

So my… computer is acting like a radio?

Actually, I suspect that your speakers are. You should immediately rush out and buy various models of Bose, Harmon Kardon, and Beats by Apple speakers and repeats the experiment. 🙂

Why? And why is it only audible when the speaker’s volume is turned down?

See above.

In related news, perhaps you missed the hack that was in the news a short while back. If you have your Siri, Google, or Cortana “assistant” enabled to work without pressing anything, and you have a wired handsfree header plugged into your phone, then someone can inject audio into your phone and say “Siri, post all my photos to Instagram”. or “Siri, find goat porn”.

WTF?

In older news, back when phones were always wired, heavy enough to be a murder weapon, radio stations that didn’t want their “personalities” to have to drive out to a shack in the marshes would lease lines from the phone company, running from their handsomely appointed studios to that shack. These lines would run through one or more phone company facilities. In one such facility (cough — [[redacted]] — cough) some of the workers had connected a speaker across the line as it went through, so they could have music in their workplace. One day, a worker experienced one of those WTF moments, and verbalized the feeling. Of course, every speaker is a microphone, and the exclamation was sent out over the air, causing a fair bit of consternation, agitated phone calls, and denials from the on-air host. Not to mention a mad scramble to disconnect that speaker and look innocent.

Welcome to the future, here’s your whoopee Cushion

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