Gremlins in my speakers
April 6, 2010 10:36 AM   Subscribe

Why do my powered computer speakers pick up interference from my cellphone, and can I make them stop?

These generic off-brand speakers and I have been through a lot together over the years. It's a 2.1 setup with a ginormous power brick. The on-switch is located on one of the the satellite speakers along with a volume knob and a bass knob.

Some history: At some point, and I don't know what triggered this, all the sound got really bassy. I responded by turning the bass knob all the way down and it sounds acceptable now, if still a bit rumbly. Also at one point I was turning the speakers on and got a painful static discharge when I touched the button. That actually happens all the time here in dry New Mexico, but on this occasion it hurt more than usual and blew out the little blue light bulb power indicator. The speakers still function like before. One last data point that's probably irrelevant: The speakers' elevation has increased by about 7,200 feet since I bought them in Florida (which is also a big decrease in humidity).

Anyway, this new issue has never occurred until I moved into my new house a couple months ago. As soon as I set the speakers up there, it began. A sporadic buzzing sound, almost like the sound of a hard drive whirring. It's quiet but loud enough to annoy (it's in my bedroom and woke me in the middle of the night once). It happens whether or not the line-in is connected to my laptop. It took me forever to realize it was related to my cellphone, but it goes nuts right before I receive a call or a text. When the phone is asleep or in the other room, there's no interference. It will occasionally start making noise on its own, which I can only assume is some background process contacting the mothership. It's an iPhone, so maybe it's the push notification service, or checking the AT&T network clock, or something. Or maybe it's the neighbor's phone on the other side of the wall (I live in a fourplex).

Since this never happened at my last home, I can't figure out what could be different here. I'm assuming that the speakers, since they're intended for use around computers, have decent magnetic shielding. Though I don't really know how that works and maybe it's degraded or something? Any suggestions to stop the sound would be great. If this is somehow a health risk, a warning about that would be great too. I'm not an electrical engineer. :-)

On preview: This old question seems to be what I'm describing. But these aren't new speakers, and they haven't had this problem before. I haven't changed the proximity of my phone to them either.
posted by The Winsome Parker Lewis to Technology (12 answers total) 2 users marked this as a favorite
posted by royalsong at 10:51 AM on April 6, 2010

Response by poster: Thanks for the link, I didn't see that one. The OP commented that a different cellphone, which broadcast in a different band, didn't cause interference. Could the problem be that my iPhone used 3G in my old city, but AT&T doesn't have 3G service at the new place, so I'm hearing interference when the phone falls back to EDGE?
posted by The Winsome Parker Lewis at 10:57 AM on April 6, 2010

Best answer: Yes, dropping down to EDGE from 3G can and often does cause this issue. If you google edge 3g interference, you'll see many with this issue.
posted by Brian Puccio at 11:18 AM on April 6, 2010

Best answer: iPhones are notoriously noisy in a studio environment. The "fix" is to put it in airplane mode when you are listening to things that require no interference.

You can't really shield monitors against GSM interference without building some pretty serious Faraday Cages around everything and using expensive shielded cable.
posted by Aquaman at 11:20 AM on April 6, 2010

Best answer: If this is somehow a health risk, a warning about that would be great too.

This is in no way a health risk -- unless you are one of the (crackpotty) people who think all the cell phone signal whizzing through the air is a health risk; it's there in the same amounts regardless of whether your speakers freak out about it or not, so don't worry about it.
posted by brainmouse at 11:23 AM on April 6, 2010

Best answer: The ferrite chokes mentioned in both previous threads do really work in my experience. They may not completely reduce sounds, but I've not noticed them since I get a speakerset with chokes on the wires.
posted by bonehead at 11:47 AM on April 6, 2010

Response by poster: Thanks, everybody, I appreciate the insight. :-)
posted by The Winsome Parker Lewis at 12:24 PM on April 6, 2010

Lifehacker recommends resting your phone on an anti-static bag to eliminate the noise. (Hopefully this doesn't impact the strength of the phone's signal or its ability to send/receive data.)
posted by steeb2er at 1:06 PM on April 6, 2010

Response by poster: Okay, a little more searching and I found the answer to this specific problem. Thanks to bonehead for tipping me off on ferrite beads/chokes, I wasn't familiar with them before.
posted by The Winsome Parker Lewis at 1:40 PM on April 6, 2010

For future reference, and perhaps to help with search terms, this kind of interference is often called "pick-up".
posted by bonehead at 2:14 PM on April 6, 2010

Response by poster: And in this very specific instance, "GSM buzz". Happens with all GSM phones near unshielded speakers, apparently.
posted by The Winsome Parker Lewis at 2:24 PM on April 6, 2010

Response by poster: Well, I bought some ferrite chokes at Radio Shack last night. I placed one on each speaker cable, as close to the speakers themselves as I could. They had no noticeable effect. I experimented by moving the chokes to different locations but nothing I tried seemed to do anything. I guess I could keep going and try more, bigger chokes, but it hardly seems worth it. Maybe it's time to get some better speakers, or just learn to live with the buzz.
posted by The Winsome Parker Lewis at 10:06 AM on April 7, 2010

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