Why your clock radio is all abuzz about your iPhone

By James Turner
October 27, 2008 | Comments: 27

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For O'Reily Media, I'm James Turner. Does this sound familiar to you?

[iPhone noise]

Perhaps you've been listening to some music?

[Music with iPhone noise]

Or maybe you've been participating in a conference call.

[Conference call with iPhone noise]

If you own an iPhone, it's more likely than not that you've run into this obnoxious sound, at one point or another. Put your iPhone next to a clock radio or too close to a phone, and you may find yourself serenaded by the iPhone staccato symphony. You don't even have to have the radio turned on, just having it close to the speaker is good enough.

I've been on more than one conference call where someone has had to be asked to have their iPhone moved away from the speakerphone, because the iPhone was stuttering over everyone's speech.

To be fair, the iPhone isn't the first phone that's been reported to have interference issues. Polycom, the speakerphone manufacturer, has been working for years to make their products cell-phone-proof, according to Jeff Rodman, the CTO and co-founder.

Rodman: We've seen it, well heard it really, quite a bit with GSM and TDMA phones. The source of this is the phone's transmitter, and what it's doing is sending its digital data broken up into very brief packets. Even when it's live, it's only transmitting about 10% of the time. But it's about 200 times a second. So what we're hearing is not so much the data itself, but the envelope, the shape of the packets as they turn on and off. And because we hear the higher frequencies much more clearly and they can interfere more easily than that basic frequency, while we wouldn't hear a 200 cycle tone, that's pretty low, when you interrupt something at that rate, it's kind of like putting a card into a bicycle wheel, you turn it from a gentle waving into a buzz, and it's the edges of that buzz we're so sensitive to.

Jonathan L. Kramer, a former Motorola RF engineer who later went on to become an attorney, and is now the principal attorney at Kramer Telecomm Law Firm, PC, is no stranger to this type of interference either.

Turner: Hopefully during this call, you'll get to hear my iPhone, which is five feet from everything else, and will be doing the Morse Code thing through the entire interview.

Kramer: Laughs

Turner: Now, it's actually more of a dat-dat-dat

Kramer: Ahhh-uhhhh-ahhhh-da-da-da

Turner: Yah, you've heard it.

Kramer: Of course.

Polycom's Rodman is no stranger either. He describes the experience of walking down a local K-Mart past a display of clock radios.

Rodman: I have a Nokia cell phone that's several years old, and if it's sending or receiving data, I can just hear that buzzing sound following me from one radio set to the next as I walk along.

Rodman believes that the iPhone may be getting singled out because it has such visibility in the marketplace right now.

Rodman: They have higher visibility just because it's the iPhone, they have more personality than just about any other wireless device right now. So if you have ten things that are interfering, and one of them's the iPhone, people are going to say "Wow, the iPhone's interfering!"

In addition, Jonathan Kramer says that the iPhone could not be sold if it didn't meet basic FCC regulations for the quality of its signal.

Kramer: All of the mobile phones, be they iPhones or Sanyos or any of the other vendors, Nokia, are required to meet the spectral purity tests of the FCC. And there are some basic regulations that the FCC says phones can't be, as we say in the transmission business, they can't be too dirty. And iPhones meet those standards, they've been certified by the FCC. But whether you're on the clean end of dirty or the dirty end of dirty, as long as you've met the FCC spec, that's what counts.

But Rodman also thinks that beyond just plain visibility, the iPhone also causes problems because there's so much high bandwidth data transfer occuring so regularly with an iPhone.

Rodman: It checks with some frequency with the wireless network to see what's coming in.

At the end of the day, however, Rodman believes that the problem may lie, not in your iPhone dear Brutus, but in your clock radio.

Rodman: There is confusion about what is responsible for this. Is it that there's one really bad model of cell phone out there that's causing the problems? Or is it that things are receiving it that shouldn't? I'm strongly of the believe that things are receiving it that shouldn't. Devices should be designed in a way that they're more resilient to stray transmitters that come along.

Engineer turned attorney Kramer explains that we can thank a specific FCC regulation for our buzzing, whinny clock radios.

Kramer: Consumer electronics, like your clock radio, your headset, the recording device you're on, all those receivers are manufactured under what's called Part 15 of the FCC rules. And Part 15 basically says, look, as a national policy, we want to encourage low-cost, relatively high-quality consumer electronics. And as a trade-off, under Part 15, it means that you as a buyer of a Part 15 device, in other words, your clock radio, in fact if you flip it over I guarantee you if the tag hasn't fallen off, there's something there that says "this device manufactured under Part 15", essentially it says that you have to accept any interference that comes into it. That's your trade-off, you get cheap consumer electronics, but you have to live with the interference that might come it.

Polycom's Rodman explains that in terms of RF interference, we may be living in a unique time in the history of consumer electronics.

Rodman: We're really in an interesting time, radio speaking, in that there hasn't been a time before, certainly in the last five years, maybe the last ten, when there was such an inordinate number of relatively high-powered personal transmitters just wandering loose in the world.

In addition, because signal strength will increase four times for a device placed twice as close to another, these phones have an optimal chance of causing interference with devices that they're placed close to.

Rodman: A cell-phone's peak power will be on the order of two or three watts, that's the most it can put out, and this is compared to a radio or TV station that puts out tens of thousands of watts, or even half a million watts, but the fact that you have so many people carrying these things, and they're putting them down, not half-miles from your hi-fi, where the radio station is, but they're putting it down a foot from the hi-fi. And it turns out if you look at the math behind how radio works, you find that the signal that the hi-fi is seeing is as strong from the cell-phone sitting a foot away as it is from a 50 kilowatt transmitter sitting a couple of blocks away.

So what's the solution to this buzzing problem? Although it's possible, with equipment you can buy at your local Radio Shack, to shield an individual device, it's probably impractical to do it for everything in your house, or everything in your world. But Rodman believes the long-term solution will come from manufacturers becoming more sensitive to RF rejection issues in their devices.

Rodman: I think there's a slow trend toward making devices more resilient to this, so that if there's a cell-phone near by, they won't turn it into a buzz, but I think that takes a while to happen. I would think someone like Consumer Reports, would grab ahold of this, and recognize "we need to start testing devices for this, start rating devices for this." Once the need was there, manufacturers would very quickly find solutions for it, because the solutions have been there, like I said earlier, for fifty years.

Reports of problems with iPhones are anecdotal, but not hard to find. Robin Preston of Coral Gables, Florida, wrote to say: Not only do I have issues with speakers (namely when I'm talking on the land-line phone in my office and the iPhone is doing a push for info or someone is calling) but my bluetooth mouse goes absolutely bonkers if my phone is between the mouse and the receiver that is connected to the computer. It is quite funny to watch actually because the mouse icon jumps around all over the screen

The problem has led some users to go to extreme measures. Dave Greenbaum wrote to say: It absolutely positively drives me insane. I work frequently at my computer and talk on the phone but now use my landline more because of the buzz problems. More importantly, I work as an onsite computer repair technician. Once a day a customer will think there is something wrong with their computer because of the buzz. My solution, which really helps, is to use a metal anti-static bag by my desk to put the phone in. Calls and text still come in, but it removes the idle buzz. I still can't talk on the phone and work on the computer at the same time though.

The FCC would not comment on the record for this piece, and Apple Computer did not return numerous phone calls requesting an interview for comment. If you absolutely have to have an iPhone, or another noisy GSM cell phone, I'll leave you with this piece of advice from Jonathan Kramer.

Kramer: Buy extremely expensive, extremely well-made devices, that may be made under Part 15, but actually do reject outside world signals.

For O'Reilly Media, this has been James Turner.

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Amateur radio operators have been suffering from neighbors blaming us for their own problems for years.

Welcome to the world of cheap, poorly-made devices.

If it's any consolation, 3G doesn't seem to do this as much as GSM. I bought a few nice pairs of Altec Lansing speakers for both my wife and I, our computers, and before we had 3G, we had GSM phones which would make the rapid-fire "tick-tick-tick" sound.

A few months ago, we had a bad thunderstorm, I noticed the 3G signal on my phone was gone, and it was doing it again. I emailed AT&T letting them know, and gave them my zipcode, and sure enough, there were a few cell towers with 3G service out that day. They fixed the issue by noon.

An important note, I _do_not_ own an iphone. This happens with any phone.

I would like someone to address what I see as a far greater issue.

clock radios can be annoying due to the interference caused be cellphones, but there are some cases where the interference can be downright deserters!

I am referring to professional audio systems. We have three theaters that I work in, 2 blackboxes and one mainstage. The mainstage 32-channel board is unaffected by cellphones, however the two smaller boards are.

Is there any sort of add on that can be used to shield audio cables from cellphones? We run a line level out of the mixer to two powered speakers in one blackbox, and the interference is particularly bad, seeing as the audience is literally right above the line level wire.

Any ideas?

On two occasions I've switched to a GSM provider only to get so frustrated with the interference that I switch back to a CDMA provider (Verizon/Sprint).

I don't see the blame falling squarely on cheap devices which are Part 15. Obviously the FCC (and AT&T) made a conscious decision to open up the GSM band in the U.S. at a frequency known to cause the most issues with consumer electronics.

I, for one, just vote with my feet and go with a CDMA provider here in the U.S.. Problem solved.

This has been happening with GSM phones for years. It is not just an iPhone thing at all. In any case, it is all about where you put your phone to avoid this. I have an iPhone and have had several other GSM phones at work as well. If I put the phone on the right side of my desk where my speakers are, I get the interference all the time, if I put it on the left side, no interference. It also seems worse if you are behind your speakers vs. in front of them.


It's unfair to single out the iPhone so much. This really does happen with any GSM phone. My old Treo 650 did it just as much as my iPhone does. Not more, not less.

It may just be that the iPhone is the first Smartphone to really start to catch on with Everyday Users who previously had 'regular' mobile phones -- which will do the same thing, but perhaps less because they're not sharing *data* like smartphones do.

I agree with Steve L. I've had a CDMA-based cellphone for years; I was surprised one day to hear the buzzing chirp one day and eventually realized that it was my employer's newly-issued AT&T phone. It interferes with several devices around my house, none of which are significantly affected by just about anything else, except when a neighbor comes over with her iPhone.

I too put the blame not just in Section 15, which I interpret "device accepts interference" to mean "device is not adversely affected by interference". I realize, having an EE background, that this is not technically current but as a lay consumer that is how I would expect the man on the street to interpret that.

I also believe there's another part of FCC regulation that state that transmitting devices won't inordinately interfere with consumer electronics; clearly it might be in the FCC's interest when one of their largest regulatees is involved to bend the rules a little bit, at the expense of consumers everywhere.

Interestingly, I had an electric shaver that I would keep on my desk. One day I set my Samsung Blackjack next to it. When it did it's 'push' for data my electric shaver would turn on by itself. Pretty cool! I could even make it do it on demand by placing the two next to each other and check my messages...sure enough the shave turns on.

Now, we've got a transmitter capable of turning on, remotely, electro-mechanical devices!


Our organization has thousands of Blackberries on AT&Ts network... most conference calls get tagged with the Blackberry Buzz.

Our more-expensive Acura is far more sensitive to iPhone interference than our much less expensive Civic (both are the same year). I also noticed that my wife's iPhone causes more interference than mine (both first generation iPhones). Hers was manufactured about 6 months after mine.

Years ago, my old Mac tower at work used to power on/off when the guy in the next room would key up his little 5w commercial radio transmitter. Phones may not put out as much power, but as stated, they are usually a lot closer to devices...

Welcome to the world of Blackberries. We've been hearing that for years. The joke is that we're ensuring we can't breed.

In other news - your mic has some really high-pitched noise coming through that I can hear when you're talking, but not during the phone conversation.

Your professional console has xlr outputs not 1/4"? Usually the interference i get is if the system is 1/4" unbalanced and not xlr balanced systems. Also, the smaller desks are plastic cased? That will also increase the interference, next time get a metal cased desk like the older Mackies.

Thanks for the comment, Michael. Yeah, next time I'll remember to run it through a low-pass first. That's what I get for trusting Audacity's "Remove Noise" functions...


We've had this for years -- the Blackberry Buzz. It seems to mostly affect computer speakers and Polycomm conference phones, but it's there. Why wasn't this article written years ago? This can't be the first time you're hearing it.

I think your article is sensationalism. As a commenter above pointed out, this has been going on for years with BB and other AT&T/GSM cell phones.

To put iPhone in the title and to suggest that people on con calls are asked "to move their iPhone" is just misleading. Anyone that knows the sound from a con call, would say Blackberry before even imagining iPhone, but most likely would just say "can someone move their cell phone away from the phone".

You even quote Polycom as saying they have been working on this for years... so why is iPhone in the title? I will guess you are a new or unknown writer that is trying for his 5 minutes of fame. You got on Slashdot, but now I have little respect for you due to your bogus "journalism".

In reply to Austin's post:
To help with pro audio equipment you can fix a lot of the issue with Neutrik's EMC series connectors which include ferrite chokes to reduce some of the RF junk that can get on the lines (since the rest of the cable is shielded it doesn't need special cable). After that you just have to be good about keeping cell radios away from the board and outboard gear if it's still susceptible.


The issue is not a function of the iPhone being the iPhone. Rather, it is a function of the underlying GSM technology for communication. GSM uses TDMA to move data (and also AT&T's old "TDMA" which is a really just another version of GSM) and it turns out that the packet structure causes a lot of transmitter harmonics that are easily demodulated by sound-producing electronics (speakers, conference phones, radios, etc.) into an audible buzz. This has to do with the timing of the packets in the time division method. CDMA multiplexes data in a different way that spreads the spectrum out more evenly resulting in harmonics that, when demodulated by these devices, are or almost are inaudible. Somewhere I think there is a communications theorem that relates the amount of lost in this way to the efficacy of data transmission through the system, but that's getting out of my realm. 3G is less prone to the issue because it is a variant of CMDA and uses the channel bandwidth more efficiently. True CDMA phones (like Verizon/Sprint) tend to be almost immune to this issue because they never go through the GSM base channel handshake on the way to 3G. The reason it's more noticeable on the iPhone is because it communicates more. I think the iPhone also spend less time on 3G that other 3G phones (Apple denies this, but I think they have optimized the radio to minimize battery drain). GSM Blackberries also have this issue.

@Andrew, I was on the phone call with James where we did ask people to move their iPhones. Call it sensationalism all you want, but it's happened multiple times.

Polycom makes speakerphones that help avoid the buzz.

The "hack" suggested by Flaherty (ferrite beads) may help a little, but chances are it won't help much.

To fix severe PC Speaker RFI in my 1.5 kW ham shack, I purchased a pair of West Mountain Radio "RF resistant" PC speakers. Designed to tolerate RF from 1 to 1000 MHz, they also seem immune to cell phone RFI (at around 1900 MHz). I can hold my AT&T (HTC) 8525 cell phone right next to these speakers and make calls or data connections all day long, and never hear a buzz. These may not be audiophile speakers, but they sure are more RF resistant than any other PC speakers I know about.


RE: Audio interference on long cable runs (any kind of RF, not just iPhone/Blackberry/GSM); Austin's post:

You need to convert from unbalanced (RCA, typically) to balanced (XLR, or "Canon" connectors typically) lines. Some boards have balanced outs; check and see if yours does that you can use.

On the other end, preamps and amps are readily available with balanced as well as unbalanced inputs, in contrast to the more common unbalanced only units you see everywhere (cheaper that way). Somewhat rarer but none the less they exist and they exist essentially for the exact reason of solving your problem.

If one or neither has balanced outs, you can convert unbalanced to balanced with transformers. They're reasonably compact and are available with the right connectors, or you can build the boxes yourself (or have them made; this is fairly common stuff familiar to any sound reinforcement or theatre-specializing repair or audio sales shop.

unbalanced from your board [RCA] --> [RCA] [short cable] [RCA]--> [RCA] balancing transformer [XLR] --> [XLR] long balanced cable with zero interference pickup [XLR] --> [XLR] balancing transformer [RCA] --> [RCA] unbalanced to your remote audio line input [short cable] [RCA].

If your board and/or line in is already balanced, it is simplified thus:
balanced from your board [XLR] --> [XLR] long balanced cable with zero interference pickup [XLR] --> [XLR] line in

If you don't have balanced ins and outs as necessary, audio-grade balancing transformers (2 per channel) will typically run perhaps a few hundred $ for all 4; alternately it's not too difficult to source a ready made "black box" made for this purpose from the usual myriad of pro audio suppliers. Then you need cable @ $.50 to $1 per foot and connectors at about $5 each; 4 in total.

You can go with any number of suppliers, some good, some not so much. Your local people may have favourites. I recommend Radial boxes and Mogami cables. An example of a single channel passive box (transformer only) is the Radial JDI Passive Direct Box. For extremely long lines or difficult RF environments (i.e. you're next to the airport), use a powered box instead/as well.

The IEEE balanced specification is specifically engineered to eliminate RF interference over long cable runs. 100~250 feet is quite typical; you can go longer if necessary. Use it; all the other theatres, sound stages, and rock-n-roll acts in the world do.

Sorry, forgot to address this one in the first post ...
RE: Ferrite beads:
People do it, I know, but Ferrite in audio lines degrades the sound quality, smears transients, etc. They work, but they are a band-aid fix and are best suited for cables that do not carry time code- or analog audio band- signals, because they screw up the signal integrity of those very two.

I guess it all depends on how deaf everyone is, and most people don't really care. But to be honest, someone will probably notice, and not say anything, but know that they know how your firm approaches things.

I recommend using it as a last resort only, and don't expect miracles. Cable runs of more than 10 feet are broadly speaking asking for trouble from RF, and ferrite ain't the answer.

As a hardware engineer years I have developed solutions for RF immunity for communication devices for many years. I have learned the audible cell phone buzz is due to these factors:
1) Non-linear devices (commonly semiconductor diodes and audio amplifier stages).
2) Transmitters operating at GHz frequencies
3) Pulse modulation digital transmission schemes
4) High RF field strength

Non-linear devices demodulate the GHz RF transmitted energy shifting the modulation envelope to the baseband frequency range. Since the latest cell phones use modulation schemes with a pulse rate of a 100Hz or so and duration of microsecond the demodulated signal is noise spectral components every hundred Hz across the audio frequency band and beyond. The amount of noticeable RF demodulation is directly related to the amount of device non-linearity and gain in the signal path. So unshielded electret microphones (with internal FET buffer) and speaker power amp inputs are the most sensitive nodes. Typically when the RF field strength is over a few volts per meter the demodulation will be noticeable.

Since practically we can't eliminate non-linear devices or keep the RF transmitter far enough away (reducing the field strength), we have to reduce the amount of RF energy at the sensitive devices. Two components are available to help: microwave capacitors (low inductance type) with self resonance above a few GHz and microwave ferrites with impedance over a few KOhms. Because of parasitic elements GHz RF energy is hard to stop from getting into electronic systems even with metal enclosures. Thus the microwave filter components should be as close as possible to the non-linear devices: i.e. across the microphone terminals, microphone preamp and the power amp inputs.


Does anyone know if buying "magnetically shielded" computer speakers makes any difference with iPhone / GSM interference? If so, any experiences or recommendations for popular / inexpensive ones (besides the COMspkr)?

I assume any "made for iPhone" certified dock / speaker systems would reject interference, but there isn't a similar designation for stand alone speakers.


Go to http://www.stopthebuzzin.com for solution.

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