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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?"
I can honestly say I've never heard of that happening before. I regularly carry a cellphone near numerous speakers and never had a problem.
I sure hope so...this drives me nuts on not only my pc speakers, but the sub for my home entertainment system too.
Move your phone to the floor or behind you, i find 2 feet away from the speakers works.
When I'm in the car, I dont put my phone in the phone holder anymore, I put it on the seat next to me.
Also dont put it next to your alarm clock, thats a bitch to be woken up to that BZZZT screech.
Turn off your cell phone. :-)
I've used a number of cell phones near many different sets of speakers over the years and have never encountered this problem.
What model phone/speakers do you use? I'll have to remember to avoid them.
Unless, of course, scissors can't cut rock...
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Never had it happen, nor have I even heard of it happening. Why would a cellphone interfere with multimedia speakers anyway?
This only happens to non-magnetically shielded el cheapo speakers.
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.
This happens to me all the time with my Cingular/ATT GSM Phone(s). RAZR V3 and MPX220 whenever it's within 2 feet of the Klipsch Pro Media Satellite speakers. Does not happen with my Sprint PPC6700 at all. Haven't had my phone(s) close enough to my home theater setup to notice if it affected that equipment.
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Faraday cage. Though this isn't practical it had to be said.
step 1. build a large box out of copper mesh screen (use wood for framing)
step 2. place speakers, computer, and user inside mesh box
step 3. leave cell phone outside of box
step 4. profit!
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.
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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.
I'd be guessing it's a notch filter at the beat frequency. GSM transmissions are notorious for this. That, and the shout-first, whisper-later protocol..
It's the GSM radio standard I think. I had this problem with my old ghetto T-Mobile Nokia phone, and I have this problem with my new Cingular Motorola phone. I don't recall what at&t operates with, but Sprint and Verizon are CDMA. Does at&t use SIM cards, or do you have to manually or OTA program them like the Sprint and Verizon hardware requires?
A B A C A B B
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!
since this seems to be more prevalent on cheap speakers, it might have something to do with either bad shields or ground loops or both. do your seakers have a wire going from computer>one speaker, and then another going from right speaker>left speaker? I believe this might be the source of the problem. replacing it with shielded wire and (or using some sort of other shield) grounding the shield might help/fix it. IANAEE, just a tinkerer. I might be talking out my ass here, so listen to the guy that corrects me instead.
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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
Yeah, this ALWAYS used to happen to me when I had a Nextel phone, circa 1999 or so -- it was particularly bad with some car stereos. I've heard it ocasionally with various GSM phones, but always with cheap cheap cheap electronic radios, and never as loud as the signal from the old nextel. Basically, I'd suggest trying a different phone (if you're using a GSM phone and can swap the SIM) or a better set of speakers, as it really does seem to be device dependent (unless we're talking the old nextel phones -- didn't they recently switch frequency ranges? if not, then maybe the current ones are an issue as well).
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.
I know exactly what your talking about, it happens all the time to my at school, the PCs we have have non-shielded speakers.
But...I just realized, it never happens at home. I have a set of 5 year old Klipsch 2.1 Speakers, that I would assume have better than normal shielding.
This problem only happens on GSM phones, not TDMA, not CDMA, not AMPS, only GSM. I beleive it has to do with the widder bandwidth used by these phones and the type of modulation they use.
In my country, we have three GSM operators, and the interference only happens with two operators. Strangely, one uses 900 MHz and one uses 1800 MHz. The one that interference doesn't happen uses 1800 MHz.
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.
Seriously, I came to this post thinking I could get some answers on this slightly annoying issue and all I get is one, big, fat, question?!? Tell something I don't already know!
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.
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I was going to post something similar about CDMA phones not doing this but you beat me to it and worded it better than I could of. I hope that this gets a + Informative mod soon.
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.
My solution wasn't to turn off the phone, but rather to turn off the speakers ... and in my last move, I placed my bed table on the opposite side of the room from my computer (and its speakers), so that I can have music when my phone is charging. ... Sadly, this means I can't roll over in bed and hack on the computer.
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Who cares? If it's that problematic turn your phone off. I'm recording music a lot of the time. At that point no phone call is important enough to leave its imprint on the audio stream. Otherwise it's a brief distraction secondary only to the phone starting ringing itself!.. Such a non story... TV capacitor whine bothers me more..
If you make little tin foil hats for your speakers, it should reduce the interference from government spy sweeps. It might work for your cell phone too, I guess.
I am not an EE, but you can try putting a ferrite core on the speaker cable.
The speaker buzzing on my system is louder when the speakers are set to a higher volume. Therefore, I have my computer set to output at maximum volume (Wav/PCM and Master channels at 100%) and my speakers are set very low. The result is that there are still buzzes, but they aren't loud enough to give headaches to me or people in the next room (my Cingular-branded Motorola Razor is exceptionally good at interfering, perhaps because its output signal strength is stronger than the average cellphone).
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I work in a cell phone store, and we're used to this. A lot of the times it's just a cheap set of speakers or a cheap component in the setup that picks up all the interference. It's a really annoying sound too. Most people should be able to get this to happen by setting their phone right next to a powered speaker (the kind that must plug into the wall and the computer) and dialing a number. Don't have the speakers on too loud when you do this. If you hear nothing, you have really good speakers. If you hear noise, your have normal speakers. :-D
~~ Please keep your arms, legs, and outright stupidity inside the ride at all times. Thank You ~~
I have never had this happen with my phone (sorry, CDMA here) but I have had the morons running illegal CB amplifiers come through on my speakers. This happens even when the amp/speakers are turned off (!). I have had this happen in my house (usually when a dump truck is driving by) and where I used to work.
I don't have anything against CB users but people running illegal amplifiers piss me off. I am a licensed ham operator and these idiots are a huge problem screwing up the bands (especially 10M). And when they come through my speakers it really is like this article describes, it almost blasts me out of my chair if I'm already listening to music (not as loud if my speakers are turned off).
I hate those asswipes so much, I wish the FCC would nail them to the wall.
I have experienced the dreaded update sounds as you describe. If you're looking for a service that doesn't interfere, I recommend T-Mobile. I have that phone on regularly and I never get interference with it. When my friends come over and have Nokia phones (I'm not sure who the provider is, but I think it's AT&T) then it gets quite annoying. T-Mobile should solve your problems (full disclosure: I do not work for T-Mobile or Nokia)
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I do get the problem with my speakers at work; generally when someone walks past with a cell phone, sometimes from my own.
I also have problems with ticking sound on my headphones and speakers, which run through an amplifier (Surround sound headphones). This is directly linked to wireless being enabled on my wireless router. In this case, placing an empty foil snack bag (like a lays chips or quaker rice snacks bag) over the small headphone amplifier box fixed it for me. I guess that the box isn't well shielded, if at all.
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its possible that the RF is being picked up by the speaker cables and traversing backwards into the amp as well. Not a feedback loop, but just RF coming over the speaker cables and interfering with the amp.
last I read, EM wave != sound wave, am I missing something?
heh, I didn't read long enough to catch the 'kidding aside'.
sorry!
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
GSM phones make a very characteristic kind of interference. It's rhythmic, brief, and I find it interesting to listen to. The obvious solution is to move your phone away from the speakers; about 1 foot is enough for me.
I have been plagued by this "feature" ever since I bought my Cingular branded GSM Treo 650.
It happens at work with my older Atlec Lansing speakers very often. It also happens in my 2001 Honda Accord.
In my Accord, turning off the radio makes the interference sound stop.
With my Altec Lansing speakers, even turning off the speakers doesn't help.
Since I live in the United States, I thought one of the purposes of our Federal Communications Commission (FCC)
was to prevent radio interference. But I guess the FCC is too busy preventing adults from watching legal porn
depicting other adults who chose to appear in those movies to deal with things like radio interference.
thats how I know my phone is gonna ring ...... Music too loud to hear the ringer
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I have the same problem all the time, but in a situation no one else here seems to have encountered: it happens in my school's Black Box Theatre. The buzzing noise will happen now and then, sometimes a few times in an hour, and drives us crazy. The speakers are top-notch (the theatre was only built 3 years ago), and it's impossible to control all the cellphones that the audience might bring in (aside from the obvious "please silence" announcement before shows). So what I'm saying is that it's not a trivial issue, in some cases. Any practical advice would be much appreciated.
I have a Nokia 7650 (GSM) that interferes with the speakers whenever it's updating to the towers or a SMS or call is coming in.
I've noticed though that depending on whether or not it's just an update of location, incoming SMS, or actual call, the pattern of the inteference and the volume differs.
I've actually learnt to ignore the location update interference - it's never very loud -, use the SMS interference to let me know without looking that I've got a message waiting, and when the speakers go,
Dit dah dah dit dah dit derrrrrr...
I pick up my phone and answer it even before it rings. :)
I suppose it could be annoying if you regularly get phone calls on your mobile, but my speakers - a cheap set of XMS 5.1 surround towers - seem to receive less interference from my phone when it's sitting about two feet to their left or right, rather than two-three feet in front.
What you should do is figure out the "sweet spot" for the level and volume of the interference. Then you can think about using the interference as another audible indicator, or just move it out of range of the speakers. :)
One thing to remember - I've noticed that it's not just the location of the phone which causes the volume of the inteference but also how loud your speakers are. This may seem logical to a number of people out there, but I never thought of it when I was first experimenting.
His name is Robert Paulsen...
GSM seems far worse in terms of causing interference to nearby amplified speakers than CDMA. I recently switched (2 years ago) from CDMA to GSM and suddenly everything I own is spewing buzzing sounds when my phone is nearby. This happens on amplified subwoofers, PC speakers, POTS telephones, and car stereos.
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.
Actually, the speakers don't matter much -- it's the cable the couples the signal back to the amp (acts like a big antenna), it feeds back to the amps inputs, and the packet rate is amplified. This is 217Hz for GSM, and about 50Hz for 802.11b. Granted, the voice coil of the speakers could also act like an antenna, but usually it's the exposed speaker wires.
1) Use better speakers with better shielding
2) Do not use mobile phone
Okay, I have put an iron-based planetoid on lay-a-way with the Ferengi, but the shipping charge is enormous! Isn't there a better way?
about putting my cell close to my head. Nope, no danger there!
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My TDMA phones would do the same thing.
I don't experience the same issues with my Verizon CDMA phone.
This will NOT work with your speakers (and amp) unplugged! There is no way that RF coupling is strong enough current to drive an 8 ohm load with audible frequency components! I'm guessing whatever speakers you're hearing this from are still on even when they are switched off -- much like your television. This is quite common for many consumer electronics with audio (clock radios, etc.)
And hey -- if I'm wrong and you've got a set of speakers that does (with no power) -- PLEASE message me the name and model so I can check it out. I work with these issues on a daily basis -- it'd be interesting to see something that refutes my experience. I've only EVER seen this as an amplifier issue -- where the high frequency coupling on the output lines feeds back to the input of the amp, thus being amplified (with enough current to drive a speaker load to an audible voltage). That's why we can generally kill these issues by putting ferrite beads and tiny caps to ground (pi-filter) right at the amplifier outputs.
Any RF engineers out there?
Calculations-wise, it doesn't seem like a huge amount of power would be necessary to do this: say a 5mV change in signal would be audible (at least very close) -- requiring only 0.625mA of current into an 8 ohm load (V=IR). That's 3uW of power induced on the line (P=VI). Pretty small, but I'm not sure how easy that is to do with an open circuit. I've never heard it -- only when the amp is on.
Systems with XLR or TLR connectors/output can remove all the inference. When cables have 3 wires inferences can be eliminated 2 wires are used for normal circuit (L/R) and one for zero level (X=0) signal.
If inputs are L and X=0, inference is I then at the end of the output we have X' = I, L' = L+I.
And it is possible to remove all inference with simple substraction
X = L' - X'
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.
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I have a phone from verizon, and never noticed this issue, however I have seen that just before a call comes in, my CRT moniter kind of buzzes out and everything looks like its being shaken back and fourth for a second.
But I never like getting calls anyways, so I chucked my phone out the window in favor of prolonging my moniters life.
Scott Swezey
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.
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Farraday cage is a much better idea than the one I had. Whatever you do, I suggest not trying to shield your subwoofer box with aluminum foil. That was a stroke of pure genius right there. No more buzzing sounds... As long as I didn't turn on the speaker...
I have a GSM-capable phone but it uses CDMA here in the US. Every so often it does check in with the local cell tower and I hear it on my speakers (even if the computer is shut off because I have externally powered speakers).
I have found that if I turn the phone so that the face plate is parallel to the speaker wires, thus turning the antenna perpendicular to the wires, the buzz minimizes dramatically. However I have an internal antenna (Nokia). I haven't played with an external antenna phone in order to see what might work in terms of reducing buzz from one of those.
Is this in any way related to the signals that make those blinky cell-phone attatchments that light up when someone calls work? Maybe a stronger signal, since those seem to work with just about every phone and this only happens to a few.
(as for some slightly useful information:)
This doesnt happen to me (Samsung SCH-A650 - 2 or 3 year old filp phone - on Verizon) but happens all the time to my friends who use Cingular (and the phones it has happened to: Another Samsung flip, LG flip, Treo III, low-end Nokia) both on their home systems and in the car, although in the car it can serve as a big bonus where you might not hear the ring/feel the vibration because of music/motion from driving. Probably varies by a mix of phone, provider, and speakers.
1. Get a BT headset.
2. Move freakin' phone out of beepedi beep distance.
3. Profit.
Fortunately, there's and even better solution today, which is to keep the signal path digital until the very last moment (inside the speaker), especially optical digital. That'll effectively remove any interference, but I'd guess it would be even more expensive.
Cheap solution: use thick cables, with kick-ass shielding, and put a fine, separately grounded metal net over them.
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The solution isn't shielding, which is impractical to do effectively after the speaker system is manufactured, but capacitive bypassing. Put a 100 to 1000 pF capacitor (of appropriate voltage rating for the audio and DC voltage present) across the speaker leads as close to the speaker as possible. The capacitor bypasses the RF current of the cell phone away from the speaker, keeping the RF voltage (and its TDMA power variations occuring at an audio rate that are causing the interference) low.
The value range is such that a capacitor in that range provides a low impedance at the RF (800-2000 MHz) while producing a negligable reactance at audio frequencies (below 20 kHz). (Capacitive reactance (in ohms) is equal to 1/(2*pi*f*C), where f is frequency in Hz and C is capacitance in Farads.)
If the speakers causing this problem are powered, you should first remove the signal cable to your computer and check if the problem persists. If it doesn't, the cause of your problem is likely to be the cable (replace with a properly shielded one or just twist with more than 1 full turn every inch it to test) or the sound card. If the problem does not go away when unplugging, the interference may still be caused by the powersupply, in case of wall-warts the cable connecting the power-suppply to the speakers, the wires connecting the speakers to each other, and of course the amplifier inside the speakers. For any of the wires, try shortening them, twisting them or replacing them with shielded ones (making sure that the shield is only connected to the ground connector on the source side). With a wall-wart stype powersupply, you can try some ferrite rings you most certainly have somewhere in a drawer, salvaged from old electronics, and twist the speaker side end of the cable around it a few times.
RF Chokes guys. That's what you want.
..a ring of iron or ferrite material around the power cable, and coated in plastic.
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..i'm too hungover! So just give it a try and it should be some help anyway.
As a few people have realised, it is high radio frequency (or RF) energy that is causing the disturbances. These cause tones at the packet rate in audio equipment, or can cause a "shimmering" effect on monitors. Now the thing about RF is that it is located far far above the audio band. So the RF energy can be removed from the leads to your audio amplifier using filtering, and it will have no (or negligble) impact on the audio frequencies.
The simplest form of filter to remove high frequencies is a series inductor. This has a low resistance to low frequencies, and a high resistance to high frequencies. So clearly, this is what you want, but what does this mean in practice? Well a form of inductor that is used specifically for removing RF can be called an RF choke.
You can find RF chokes on the power supply cables of most laptops. Just before the connector that plugs into the laptop you might find a little cylinder around the wire. This is in fact an RF choke.
Wurth Elektronik are the best ferrite component supplier I know of. They know what they are talking about. The link below shows one of their RF chokes.
http://www.we-online.com/we_web/emc/eisos/alg/kat
If you felt like spending some money, you could get a few of these chokes (also called EMI suppressors) and clip them around the ends of all your audio leads, and hey presto, the problem would be solved. These are already built in to lots of equipment which is why some speakers and amplifiers dont pick up any mobile phone noises.
But instead of opening your pocked to buy these, you can make an RF choke very easily. If you can find an iron ring, then just loop your audio cable around the ring a few times and that will suppress the RF energy too.
Ideally you would use one of these: http://www.we-online.com/we_web/emc/eisos/alg/kat
But any piece of iron will do, ideally in a ring. Even if it is not in a ring, like just a heavy bolt will do. Wrap your audio cables a few times around the iron, so it becomes a coil with the iron through the centre. This is a simple inductor and will give you some attenuation in the RF power getting in to your audio system.
Now that i think of it, maybe if you have a few heavy iron washers lying around, they might work well as a primitive RF choke.
I havent bothered to do any of the maths on this,
-Vince
*yeah, I am an RF engineer.
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.
Just move the phone away from the speakers. The transmission's power drops with the square of the distance.
If the phone is a couple feet away on your belt and you still hear interference on the speakers, consider getting a different phone/carrier. Its also pumping that energy into your hip and other nearby sensitive areas.
Moderating "-1, Disagree" is simple censorship. Have the guts to post your opinion.
I work with TDMA and low to SHF+ bands of frequencies on a daily basis, with multiple media of communication. It never occurred to me when my cell phone buzzed the hell out of my subwoofer (it never bothered the satellite speakers) on my home PC that TDMA was the reason. I've always disliked the cheap-o method of Multiple Access, but now I really hate it!
Well, I'm due for a new phone in a few months anyway...I'll just have to do my homework beforehand. At worst I'll just build a simple shielding around my sub and get new speaker cables with a better di-electric.
Man I feel dumb for not thinking of this earlier.
What else can happen when an unstoppable force collides with an immovable object?
Nextel is not GSM-based, they use Motorola iDEN, which is its own standard.
I believe that in terms of modulation schemes, iDEN is a close relative of GSM, and GSM phones are notorious for these problems.
retrorocket.o not found, launch anyway?
It's a protocol and modulation suite that happens to include a defined codec, often referred to simply as the "GSM codec", since it is the codec used by the GSM suite.
retrorocket.o not found, launch anyway?
Hmm -- could be there was still some power left in that wall-wart. They can sometimes take very LONG times to discharge if the circuit is open (days even). I have a hard time believing the RF coupling could drive speakers without some sort of amplification -- just because my experience says otherwise (and I've looked at quite a few setups at my job -- it's one of our biggest problems with audio systems). The real test is if the speakers would do this as just a wire connected to a speaker driver. It sounds like you had a set of powered speakers -- so this isn't exactly possible. Interesting though. Anyone else definitely seen (err.. heard) this with unpowered speakers?
Actually balanced amps won't work either. I've seen this happen with fully differential amplifiers as well as pure single-ended versions. The problem is that the signal doesn't couple uniformly, and with a differential amplifier -- the difference between the two signal lines gets amplified. It's also imperative that PC board layouts be done correctly to minimize RF coupling, since long, exposed, traces on the board can also couple RF. Smart manufactureres sandwich signal lines on the inner layers of boards (between power and ground planes) for extra shielding.
Mostly, however, Pi-filters on the inputs/outputs to an amplifier board (with all signal lines from then on run inside the board), and shielding where the problems are really nasty is the only way to truly kill RF. The cheap cables with metal net should work great for that.
Digital is great because of it's relative noise immunity, but you've got to turn it back to analog at some point -- and that typically means the speaker cables are going to pick it up (always analog -- even with class D amps). If your amp is in a metal box it should be safe from the outside regardless of design choices -- it'll only be the external wires that let signals in.
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
Hmm, you beat me to my comment.
Seriously, I would rather saw off my foot with a rusty spoon than go back to Verizon.
There are very strict regulations for emissions from computer equipment, so how it it legal for mobile phones to emit such ludicrous amounts of interference? I remember reading that several computer companies in the 80's had problems getting their computers (in plastic cases) past the regulations.
When I worked with VT terminals I remember the screen used to completely freak out when a mobile phone rang, and the speakers on my PC would start buzzing. I was amazed that this was allowed, and still am.
Can anyone explain?
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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
Turn the damned thing off. You dont need it anyway.
---- Booth was a patriot ----
$110 for a 2.1 speaker system is not expensive. That's not even midrange. I'm not trying to be obnoxious here, but a good set of headphones will set you back more than that.
That said, the cellphone-interference problem doesn't seem to be related to the type of speakers in use; there are other people in the thread using what I would consider to be high-end equipment and they're still experiencing problems.
FYIW, I don't get this problem in my home system, I only get it in my car. I'll try leaving my GSM phone on top of one of my speakers though and see if it happens, just to check -- normally my phone is on top of the source equipment and it doesn't do a thing, and some of them are feeding unbalanced lines so I'd expect that's where the problem would occur.
"Ladies and gentlemen, my killbot features Lotus Notes and a machine gun. It is the finest available."
You can hear that kind of noise here, just recorded for your listening pleasure.
I called my own cell phone from another cell phone. My cell was right next to the speakers and the other one was about 1.5 meters away. The "bzzpt" starts before the call arrives and it is only displayed in the phone when it starts ringing.
Ok, seriously...add a little series inductance to the power and audio cables, and some parallel capacitance. You want to allow audio frequencies to pass...but nothing at much higher frequencies. The parallel caps allow high frequency A/C to short across while the inductors look like open circuits to the A/C.
You can try just adding some inductance by wrapping the cords around a metal core. This can work quite well by itself even.
Nextel uses a highly bastardized hodgepodge of technologies to work. Part of the system IS GSM because you can take the SIM card from any Nextel and put it into a unlocked GSM phone, and use it for international roaming (you get charged out the ass, but it works)
Not that it really matters anyways.... iDen will be gone in about two years. Good riddance...
(I sell T-Mobile, Sprint and Nextel... and I hate Nextel.)
Viva La Revolucion! Buy a Mac!
Try and have a listen to the record 'Mario Piu - Communication', it that actually samples the phone interference!
3 L/qid=1144591269/sr=8-2/ref=sr_8_xs_ap_i2_xgl/203- 1975359-1528719
http://www.amazon.co.uk/exec/obidos/ASIN/B00004T4
I can't remember what it was called but there was another tune around the same time (98-99?) that sampled the 14.4k modem handshake.
- doctea
Uh... what you call 'interference' they call 'signal'. How else would a cell phone work if it didn't emit an RF signal?
Unless this state is something that happens to you unexpectedly, it should be a simple thing to turn your mobile phone off. That's what I do. If people calling really want to talk to me, they will leave a message such that I can call them back.
My opinion? See above.
Last year I was at a local rock concert for the band Lamb. If you know this band, there are lots of quiet bits in their music. Anyway, in the middle of a really long track the music went into a quiet part, and everyone was in the mood, right into the music... then all of a sudden there was the all-too familiar BA-DUDU-BA-DUDU-BA-DUDU-BA through the speakers, twice as loud as the band itself.
The crowd broke out of their musically-induced trance and burst into laughter, and it totally fucked up the rest of the concert.
It turns out the sound engineer left his phone on the mixing console. Duh!
It's not interference or noise - it's the signal that they are meant to transmit, and are licenced to do so by the FCC (or appropriate authorities elsewhere).
The problem is with poor quality, unshielded amplification circuits and computer monitors working poorly when being near any RF source.
I've never had this problem, my phone doesnt interfear with any of my audio equipment, however one of my friends used to have a TV that when his phone rang would lose its horizontal hold and go a bit crazy.
To err is human. To forgive is not company policy.
I worked with a gal a few years ago who had a similar thing happen with her pacemaker. We all kept our phones off, but occasionally someone would forget, or a service man would be unaware and have his phone on. She would look up a second or so before the persons phone rang and immediatly walk away from the area. I never really talked to her about it, but I'd guess its the same type of interference.
I have two aspects of this to comment on, and it is actual information from experience. I have had this happen a lot with my cell phone interfering with the speakers of the guy I shared a cubicle with. Several people have proposed that the problem happens just because the phone is sitting right next to the speaker, and if you move it a little farther away, it fixes the problem. That is not correct. The signal does not drop off that quickly. I mean, it's communicating with a cell tower hundreds/thousands of feet away, so it's probably not going to disappear from moving it a foot away. In my case, my phone was on my desk, and my cubemate's speakers were about 5 feet away. The method of moving the phone does work to some extent, but it's effective based on positioning, rather than distance. While my phone was buzzing my cubemate's speakers, I could turn the phone different ways, and the buzzing would come and go.
The other quick fact is about the types of phones. I've heard a couple of people say only GSM phones do this. Mine is a Nokia 8260 on the older AT&T TDMA network, so it also does it. From the other reports, it sounds like Verizon's network (CDMA) may be one of the few that doesn't, although I don't think we've heard from Sprint people yet, and I don't know what kind of network they use.
We may experience some slight turbulence and then...explode. -Capt. Mal Reynolds
Nextel phones seem to be notorious for this - also, its not just pc speakers, tv's, radios, standard wired phones - if there is a nextel phone around when using one of these, you will usually hear interference.