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How to Avoid Mobile Phone Interference w/ Speakers
EnzoTen asks: "Everyone has been sitting at their desk rockin, jamming, or groovin to their favorite tunes. You are in a trance, getting work done... then... BZZZPT... BZZTP..BTT.. BZZZZZZZZPTT... the blood curdling noise of your cell phone interferes with your desktop speakers playing 4 times the volume of your music and it takes everything in you not to flip your desk upside down, or throw your mobile phone across the room. Is there anyway to avoid mobile phones interfering with speakers? Are there speakers available that are shielded from this type of interference?"
Turn off your cell phone. :-)
happens all the time for me.. the only good thing is, is that if you are paranoid, you'll know when your cellphone talks to the tower.. you won't know what of your private information it is giving away.. but you'll at least know when it gives it away ;)
--hmhansolo --lnxmstr --gentooman
it happens to me with my ATT/Cingular GSM phones and affects both of my car stereo systems and my desktop speakers, but not my hifi/amp setup. It's not as annoying as the submitter describes, but it's a very audible, very noticeable series of clicks and burps. Lasts about three seconds, every ten, fifteen minutes. I assume it's interference from some kind of GSM syncrohnisation signal, but I'm not an EE. :)
-EvilMagnus
Comment removed based on user account deletion
Sounds like you're getting Electromagnetic Interference (EMI) or Radio Frequency Interference (RFI).
Both are the result of either bad or cheap shielding. Most consumer electronic devices should have at least some shielding.
Look for frayed speaker wires. Look for cracks in your cell phone case (the one it's made out of, not the cool "leather" one you got when you bought it).
Either get new speakers, or replace your cell phone. Or both.
Reeses
This problem affects GSM phones much more than CDMA phones. GSM uses a time-division scheme, where the phones transmit in 570ns bursts, at a rate of around 217 bursts/sec.
I have the same experience. It really is very, very annoying.
One of the RF techs at my company apparently modified his computer speakers to filter out the noise. I'd like to find out exactly what it was that he did.
The solution is to properly shield the speakers and speaker wire. The speaker wire behaves like an antenna, coupling the signal into the audio amplifier, where it is detected and amplified. It's behaving like a crystal radio, a primitive type of AM radio receiver.
Mea navis aericumbens anguillis abundat
i'm frankly a bit surprised that so many people don't know what you're talking about - i know it very well, and it even affects my monitors.i actually like it -you get to see how long the cell-tower to phone negotiating takes, since it starts happening a couple of seconds before the phone actually rings or receives a SMS.
the solution, i guess, is simply to use more expensive shielded speakers, since that's what faraday cages do.
Cell phones probably aren't powerful enough to cause cancer, but they sure as hell aren't powerful enough to drive a speaker cone from across the room.
But hey, why listen to me? This article by an electronics engineer was just a quick google search away!
I moved my phone about 17 inches to the right. Worked fine.
Seriously, just move the speakers and phone placement until they don't interfere with each other. A couple decades ago every bit of electronics you bought came with a piece of paper that told you to do this if you got radio or television interference. I always thought it was silly, but maybe that slip of paper needs to go back into boxes.
--
Evan
"$30 for the One True Ring. $10 each additional ring!" -- JRR "Bob" Tolkien
In my experience this is the telltale sign of an incoming GSM call. There's been a couple of occasions when colleagues' cellphones have gone off and caused this interference on a speakerphone. This is is a faux pas since our parent company's cell network is _not_ GSM. Of course, this is not something I take seriously, rather I find it amusing.
This definitely does not occur with the CDMA phones that we use (and our company prefers, for other reasons.)
There are two places you can solve this problem:
#1, get a better cell phone. With TDMA phones (GSM, D-AMPS, iDEN) you get a lot of noise as the transceiver switches on and off several times a second, transmitting at full power. iDEN phones (NexTel) have always been *by far* the worst about this, in my experience. If you get a CDMA phone (eg, Verizon), the phones on a cell share a common, continuous, low-level signal, which does not cause this kind of interference.
#2, shield your amplifier. (In cheap computer speakers, it's built into one of the speakers, or the subwoofer.) Surround it in tin foil, and ground the foil. Other possibilities are poor grounding on the signal wire - replace it with a shielded wire, and ground the shield to your computer's case and where it reaches the amp.
The interference is a clicking, somewhat like a rotary phone (I now feel old). It happens when the phone is talking to the tower. I kind of like it as it occurs a second or so before an incoming call starts ringing. It also occurs at random (or maybe regular?) intervals.
It bugged me with one set of speakers that were arranged such that it was fairly loud. I moved the phone, and it fixed the problem. My new speakers click more subtly, and I don't really mind it. I think it may have more to do with the volume settings on my computer and on the speakers than the brand of the speakers.
--
Evan
"$30 for the One True Ring. $10 each additional ring!" -- JRR "Bob" Tolkien
90% of the time it happens just before I get a call/text, so I quite like the early warning.
Come as you are, do what you must, be who you will.
I hear this during press conferences all the time on live tv. It really isn't a bzzz, but more of a repeating, rapid blip-budup-budup-budup... Listen for it, it happens a lot. In san francisco, it used to happen near the cellphone antenna's on my old walkman.
Laboratree - Scientific collaboration based on OpenSocial.
Just wrap your cellphone in several layers of tinfoil. Problem solved.
Kidding aside, the worry over cellphones is the damage that might result from the RF energy being emitted. However RF energy is non-ionizing radiation, so the frequency is way too low to do any sort of damage to your DNA. I believe it's media fueled hype, but I'm not an expert on the subject.
Either way, the real danger that cell phones present are when someone happens to be using one and driving a car.
There a few different paths you might take. You don't say anything about the model or brand of speakers, that seems to make a difference. The cheaper ones might have insubstantial cable shielding at best.
My home computer is connected to a reciever that powers separate speakers, I don't really get any problems.
If you were really obsessed, you might get a higher end sound card with balanced audio out, with powered speakers with balanced inputs. If you have cheaper speakers with cheap built-in amps, then the long, unbalanced cable can act as an antenna. I've found that switching to balanced audio connections is the best way to minimize picking up stray noise on the analog, much better than getting "high end" RCA cables. Switching to XLR (balanced) cables drops the amount of noise significantly in just about any analog audio path.
Or you could switch to speakers that have a digital inputs. That's probably a lot cheaper to get into.
This happens with amplifiers, speakers, and CRT monitors if the phone is near them when the phone is actively sending data/voice.
If my phone has an active call and I move it near my keyboard, my keyboard stops functioning. Discovered this by chance one day while on hold.
What the hell is my phone transmitting when i'm not receiving a call?
It's periodically sending your GPS location to the government who's building a huge database of people's movements, to correlate against all sorts of crimes ranging from terrorist attacks and murders to petty theft and jaywalking.
The RIAA has shown interest in this as well. They want access to the data so they can draw up a list of people who walked by a record store without stepping inside and buying a CD. They claim it's not only in their own interest, but for national security as well, since anyone found guilty of such a crime is a threat to the national economy, and therefore a terrorist. But don't worry, the government is protecting you and is fiercely negotiating with the RIAA on your behalf. They finally realised what a bunch of nutcases these RIAA folk really are, they're sick of being pushed around by some corporate lobbyists, and are now actively pushing for a rewrite of that RIAA bill that would change the wording from "terrorism" to a mere "theft". And it looks like they might even have a chance of winning this one...
OK, and now for the serious answer: a cellphone tower can only support a limited number of simultaneously connected cellphones. It therefore needs to know exactly when a cellphone leaves its range, or disconnects from the network altogether, so it can free up its connection slot for use by another cellphone. Normally a phone communicates a disconnect to the tower whenever possible (for example if it's getting out of reach and connects to another tower, it then disconnects from the first and the connection gets transferred gracefully from the old tower to the new one, even in the middle of a conversation). However, if you just yank out the batteries, the phone gets utterly destroyed, you suddenly enter a cage of faraday or even an underground tunnel, ... the phone will have no time to notify the tower, so the tower needs to check up on supposedly connected phones from time to time to check that none of them are MIA. It's basically similar to an ICMP ping on the Internet. And that's what you hear over your speakers. Similar thing happens right before a call or SMS comes in, or when you dial out: there's two-way communication, and the RF interference the cellphone puts out is picked up by your audio equipment.
Install windows on my workstation? You crazy? Got any idea how much I paid for the damn thing?
GSM is a TDMA (Time Division Multiple Access) system. This means a single physical channel is divided up in time for multiple people to share. A single physical channel is just a frequency range, such as 890-890.2 MHz. Each physical channel is divided up in time into what are called timeslots. Timeslots are grouped by 8's into what are called frames. Each timeslot lasts 0.577ms, and a frame is 4.615ms. When your phone is communicating with the base it is assigned a single timeslot in each frame. This means it is transmitting ON off off off off off off off ON off off... and the ON's are spaced 4.615ms apart (the frame duration). 1/4.615ms gives you 216.7Hz, which means that if (when?) it is picked up by other electronics, it is most definitely in the audio band and you will hear it. The RF transmissions die off very rapidly with distance from the antenna, which is why moving the phone a small distance away is sufficient. What else... when you hear the interference before receiving a call/SMS, this is what is happening 1) one or more base stations broadcast "hey you" to the geographic region where your phone is (your phone is always listening for this) 2) your phone contacts a specific base station requesting a channel (AUDIBLE) 3) the base station responds, assigning a channel 4) your phone goes to that channel, authenticates, etc. (AUDIBLE) 5) phone finally rings / SMS is sent
Slashdot comments at its best. Useless.
If you do not recognize the problem, it just might be that you
a) do not experience it -> cannot help.
b) do not hear it -> cannot help.
c) notice it, but do not want to help!
In every case, it might have been a good idea to wait and see if more
intelligent and/or helpful people chime in, and might provide an answer to
the riddle. And until that time, just shut up. You probably will just look
foolish if you try otherwise .
I actually *understand* the physics behind that phenomenon, and alas, there
is no better solution than what was provided in another response: put your
cell phone at least one foot away from the speakers. The problem is Maxwell:
in order to send a signal successfully to the next station (remember: this
is most likely indoors, as speakers are less usefull outside, and thus, there
is probably a wall, which has to be penetrated by electromagnetic waves) the
cell phone has to "pump up the volume".
The energy is degrading with the second power of the distance to the cell
phone, so: putting it at double distance to the speaker (or the next
station, for that matter) will lower the received energy by 75%. Same is true
for the station, but that is farther away to begin with.
educating people every day,
Dscho
As an audio applications engineer for a large semiconductor company -- this is the single biggest compaint we have from customers using CMOS IC amplifiers. You will get it from almost any audio system that's near a cell phone (or 802.11b RF transmitter -- they have 50Hz packet rates that are audible from the 2.4GHz baseband signal).
What ususlaly catches it is the speaker wires -- they act like giant antennas. 900MHz and up takes only a few centimeters to make a decent antenna, so long speaker cables are a prime target. The high frequncy (which you can't hear) couples on the output lines (typically) and goes back through the gain setting resistors on the amp to rech the amplifier input, where the packet rate (not the 2.4GHz to 900MHz baseband) is rectified and amplified. What you hear is the resulting buzz.
Your cell phone itself doesn't shield this -- then it wouldn't work! The best thing to do is to shield your speakers, wire, and audio system it may be near. A faraday cage (as described by others here) will work great. Plastic-metallic shielding (like that used in anti-static IC or computer part bags) also works wonders.
This never happened to me back in the US but here in Iraq it happens all the time. I thought it was just the frequencies they use here. As far as I see it there are five solutions to this problem:
1) Keep your phone away from your speakers
2) Buy better shielded speakers
3) Enclose your speakers in a faraday cage and ground the cage
4) Enclose your phone in a faraday cage (note this may make it difficult to dial, oh yeah and it will negatively affect your signal quality too)
5) Get a new phone
Personnally, as stated above, I find it rather conveniant to get an early warning when I'm going to get a call. Besides, if you think of it as sounding like music they'd play at a rave it's not so bad. Bip bada-bip bada-bip bada-bip. Sounds kinda like techno.
War(n) - Gods way of teaching Americans geography.
I had this problem at work, where I had some cheap $20 speakers I bought at Office Depot or OfficeMax. The buzzing annoyed me so I took the speakers back and bought some $30 ones. Not too much more expensive, but a huge difference in quality. I still put my cell phone in the usual place, right next to the left speaker, but I've never had the buzzing problem since.
At home I tend to put my cell on my desk next to one of the speakers. The speakers are just a $50 2.1 set I bought a few years ago. They've never done the buzzing thing.
So overall, I have only encountered the problem with cheap speakers. Just a slight upgrade made a huge difference, not just with this problem but in sound quality and general sturdiness. Obviously there are a thousand phone models, and mine is just one of them. I thought I'd put my experience out there at least.
Stop the Slashdot Effect! Don't read the articles!
Use pro-level gear that has balanced connections on XLR or TRS jacks. Balanced cables have three conductors carrying ground, the signal, and a copy of the signal 180 degrees out of phase. Any interference affects both signal lines identically, so when they are put back in phase at the other end, any interference will be phase cancelled as it will now be 180 degrees out of phase.
The source of this noise is the actual digital communication between your phone and the cell tower. There's nothing wrong with the phone, it's probably your speaker wiring that's picking up this signal as interference, as cheap wires have absolutely no shielding. If you don't know what kind of wiring you have, then you have cheap wiring :)
:D
The cellular signal is rather strong and because of the way it is modulated, it has tons of noise outside its nominal band, almost all the way down to DC. In plain english (well sort of) this means it's feeding square waves into your speakers. Square waves are the "loudest" waves due to their harmonic constituents, which is why the noise can scare you shitless compared to your regular music content. Square waves are that loud annoying "bzzt" family of sounds in techno music, like Benny Benassi
Using better wiring will decrease the amount of noise picked up, but I find that even with extremely good wiring you can still hear a tiny bit of phone interference. I kind of like it because I have a rather potent car stereo and I couldn't hear the phone ringing if it weren't for the interference, but it is sufficiently dampened that non-audiophiles won't notice.
-Billco, Fnarg.com
The Original Poster didn't say if his office speakers were wired or wireless.
I've never experienced radiowave interference on my wired speakers, but know my house (neighborhood?) is nasty on radiowave interference. I tried purchasing some FM-speakers, but they couldn't receive a clean signal
across my living room.
How is your network connection? Wired or wireless? Could it be the network signal being messed with before it hits your computer and you computer just amplifies and echo's out the interference?
I strongly doubt it's in the speaker wires. While I remember a friend of mine in college would play tricks on guys living in the next dorm room, he had a ham radio license and foot long antenna. Still he had to be less than a foot to cause the interference you are talking about -- holding the antenna parallel to the speaker wire that ran along the edge of next door room. Any farther, or disorient the antenna (not parallel to speaker
wire) and there was no interference. He only did a few times when they were cranking music too loud -- they thought it was a problem in their setup, so they stopped cranking it so loud...:-)
However, a cellphone, given it's small antenna and the lower power (his ham setup ~10-30W; modern cellphone: max 3W), it would be hard pressed to generate the same interference.
I'd look to other causes than a cellphone for interference in wired speakers.
However, for 1/8th inch connector thin-wire computer audio, most of the wire I see is shielded. RadioShack sells shielded and unshielded audio cable in lengths up to 20-30 feet. It's not that expensive: less than 20 bucks for a 20 foot extension cord last time I bought some.
Good luck.
-l