For a long time I’ve noticed that my car’s stereo would sometimes “act up”. It makes this staccato sound, almost like an old telegraph. When the blips get dense enough, it actually sounds a sort of tone – a bit reedy, and I’m guessing in the 400-500 Hz range. I figure it’s trying to produce that tone, but usually it doesn’t sound long enough at once to register as anything more than a series of blips.
Anyhow, I’d chalked it up to my car being about ten years old. Then I was hanging out at a friend’s house a few months ago and her (external) computer speakers started doing the same thing. We fixed it by unplugging them from their power source. It’s happened pretty much every time I’ve been over there, and she swears up and down that it never happens when I’m not around.
Then this weekend at a conference, the wall-mounted speakers did the same thing, and in the middle of somebody’s talk no less. None of the organizers (in whose home department this conference was being held) had ever known it to happen before.
So, am I emitting some sort of radiation that insufficiently shielded speakers pick up?
Are you sure you don’t have a defect in your cell phone? A friend had one once that caused computer monitors to behave in a similar way: constant high frequency ‘flickering’. Took him weeks to work out what was happening. Replaced the phone, problem vanished.
I’m going to second the cell-phone thing. With most computer speakers, you can tell that a nearby phone is going to ring a second or two before it actually does, as the phone does some communicating to the tower.
Non-defective GSM phones of certain band frequencies will make speakers go haywire in this rythmic morse-code like pattern when a) about to ring/receiving a text message b) communicating with the tower to check if there’s voice mail c) using online services. I can actually know when my phone is ringing by flicker in the CRT monitor I have at work a few seconds before it actually rings.
Ditto on the cell phone thing. I have had several and had this problem in spades with a Nextel phone. I think their protocol is proprietary rather than the CMDA used by most other US digital carriers.
Is there any way to test this? It almost never rings/receives a message right after the sound, and I never use online services. I’ve never noticed a CRT issue. The voice-mail check could be it, but why would it only happen sometimes? Does the phone really check for voice mail that sporadically?
I always get the sound when getting a call/message. What I can voice mail check might not be, in fact, since voice mail might be “pushed” like text messages. However my phone does, roughly every 10 minutes or so, contact the tower because I can hear it through the speakers. Try putting your phone on the speaker and calling it.