Honey bees took my cell phone!

As I have tried to explain here on the CR4 threads it is the wave shape of the digital signal. Too many people have displayed their ignorance over this important factor. The signal has a rectangular shape (pulse wave) and has a very high power density. I know that the over all power may be low but the individual pulse as previously explained has a very fast rise time (that is it gets from zero to its full amplitude in pico seconds and the pulses are sent in packets the instantaneous result is you get a powerful magnetic field. It is very similar to a radar signal. The first time I saw this type of wave form it was from a transponder (secondary radar device used by aircraft to show who they are on the main radar display) Ok these shoot out the equivalent of a thousand watts instantaneously, but the mean power is only about 100 watts. We were warned about the physiological affects of standing anywhere close by. They were kind of nasty. When news crews do outside broadcasts and a phone starts up you can hear the buzz as the signal is transmitted. So it is of no surprise to read what you have found. In twenty or so years we will look back and say how stupid were we to have gone digital.

You know, the more you and Blink talk about this subject, the scarier it gets! James

I've seen this effect too, and no I can't explain it.

You could test your theory with an unconnected speaker, though.

It's hard to imagine that there's enough power there to wiggle a tweeter, but even harder to imagine that there's enough power there to power the electronics to wiggle the tweeter.

So, I don't know. And I don't like it.

Take a small speaker say a 2.5" and connect a small coil across the its terminals then apply your phone. Let us know what happens.

http://www.maxim-ic.com/appnotes.cfm/an_pk/3880

With Google, all things are possible.

...One particularly critical example of this problem is GSM (Global System for Mobile Communications) cellular phone systems. The GSM standard uses Time Division Multiple Access (TDMA) to allow multiple phones to communicate simultaneously with a base station. GSM phones transmit data in bursts at a frequency of 217Hz. The result is an electric field strongly modulated at 217Hz, well within the audible band. Although GSM phones operate at frequencies ranging between 800MHz to 1900MHz, the 217Hz envelope frequency is consistent.

Thanks! Good article.

I've tentatively concluded that this sound will occur without any electronics (other than the cell phone generating the effect) -- i.e, just a speaker. As I think about where I've heard it (near my computer speakers, near my clock radio, near my (musical) keyboard) the audio amplitude is always about the same, and affected by cell - speaker distance. Ooooh -- just occurred to me -- my keyboard is stereo. I could put the phone near one side (I'm sure there is just one stereo amp) and see if both speakers are affected.

Kinda gives me the willies to think that these signals are so strong.

Dear Bhankiii

Good god. You have read all that at Maxim web site of 217Hz. Sharp eye indeed and excellent for the CR4.

FUnny, just posted this, below, before reading a couple new posts (above), which make it all a lot clearer. I was going to say the sound was about 200 hz. Do I get some sort of music prize?

So, it appears that these turned-off devices are amplifying the cell phone signal, without being turned on.

Talking to myself:

On the other hand, amplifying is really the wrong term here. If the phone is putting out 5 watts, and the speaker is putting out a sound that is clearly audible, but not loud, then perhaps the input to the speaker is only 10 milliwatts? And I suppose the speaker mechanically filters out the carrier frequency, leaving the audible components to be heard. Further, what I am hearing is probably not "really" an audio signal, but more likely little bursts that happen to be spaced at audio frequencies. But all this is a guess.

You really worry when your cell phone is off and it rings when walking past a speaker that is disconnected and they have a conversation.

... and then Rod Serling walks in!

http://cr4.globalspec.com/thread/7285/Security-agencies-do-they-put-in-questions-to-see-what-we-will-disclose

One is never alone with a mobile phone: some people even take them into the toilet so as not to miss a call. How abstruse!

Phone companies world-wide have done considerable research into the physiological and psychological effects of these electromagnetic emissions and they have come to the conclusion that there are none. Now, how on Earth can that be?

Experiments here are based upon getting other peoples' phones to work underwater and to survive impacts with large, heavy objects, like a carpenter's mallet (consider this to be encouraging evolution by natural selection). All have failed so far, though as the sample tested here is statistically insignificant, considerably more effort is needed to produce a valid result over an experimental programme that extends way into the future. Naturally, the experiments are undertaked within the guidelines provided by the European Economic Community's WEEE Directive 2002/96/EC...

Now we know the cause of global warming it is all that under water microwave radiation. Only VLF works under water and then only to a few metres. Give carpenters soft rubber mallets.

ELF is what you want for underwater. That, or whale song.

Extra Low Frequency. (Not ELO Electric Light Orchesrta.) The military use very low frequency tranmitters to comunicate with their subs. 45KHz to 65KHz. It is thought the magnetic portion of the wave penertrates the water. If you tell any one I will have to shoot you.

I actually designed the control panel for the navy's ELF system back in the late 70's - so it is I that shall have to shoot you. (BTW, the freq range is Hz, not KHz).

The ELF system was just recently retired, after 20 something years of happily talking to submarines.

Naw definately not that low I wrote the manuals.

http://en.wikipedia.org/wiki/Extremely_low_frequency

I tried it with my cell phone and my headphones, but couldn't hear anything. If the RF is getting rectified somehow, you could be detecting the envelope of the RF signal.

Are they shielded?

you could be detecting the envelope of the RF signal

Yes, I think that is exactly right. Part of he problem with experimenting with this is the sound only occurs occasionally -- when experimenting with my keyboard last night, the sound was definitely produced when the keyboard was switched on... but when I got over to it to switch it off, the pattern of tones had stopped. Then, when I switched it back on, the tones reappeared within a second or two... But maybe that means I just happened to be out of synch (or in synch, depending on perspective)?

I distinctly remember the sound emanating from a switched-off radio (which I remember because it seemed so odd). But the radio's amplifier may be active all the time, because it is also used for the alarm, I suppose.

This would be much easier to test if I could make the phone do it's thing on command. (Maybe cycling the phone's power?)

Whoopee! it worked. Cycling the power does cause the tone sequence, and yes, it does appear to require amplification (at least with my shielded computer speakers). So, my brain cells are being killed off at a lower rate than I would otherwise have thought... I guess. Now that I can make it do its thing on command, I'll try it again with speakers alone -- both open circuited and closed.

BTW... the phone is now about 8" from one of my speakers, and about the same distance from my monitor. When it does its thing, the monitor flickers, too.

I too have noticed the buzz sound on speakers before, although I tried doing it with my phone just now, next to my speakers and nothing happened. I concluded that only speakers that are not designed very well, have some flaw in the shielding (the speakers I tested on were shielded computer speakers), or the signal is somehow propagated to the speaker wires, and amplified by the speaker amplifier. I tried it with headphones, and nothing happened either. I will have to try the coil idea, and hook that up to a speaker, to see if I can get any sound out of it. I know that in computers, high frequency devices like network adapters can make background buzzing in speakers that are hooked up to that computer. I can actually hear a high pitched sound when the network activity light flashes if I have the volume up.

I have noticed other weird things with speakers before, once I made a source input cable for some speakers (and the hacked up cable failed somehow, it shorted one of the channels to ground I think). With the speakers on, and not plugged into any source it seemed to be picking up a radio station! For a minute or two, it freaked me out hearing voices in the speakers! Some other speakers did the same thing too. My thought was with that channel shorted, the cable with it's capacitance value, oscillated in a way to be tuned to that radio station.

Now how does a phone, as small as it is transmit 200 some hz waves so effectively? I thought you had to have a massive antenna to accommodate for the length of the wave.

And I always thought that the frequencies used in phones were low enough energy waves, that it wouldn't be enough to cause damage... ie not high enough energy to displace DNA molecules and damage them, so it would just takes many watts of those frequencies to cause damage. Of course, that could just be a complete misconception of mine.

Nick

Lets staighten this out a mobile phone when on has to talk to the base station every so often the digital signal is made up of bunches of pulses that are refered to as a data package. These data bursts are then repeated at 217Hz intervals. It is these packets that cause the buzzing chirping noises. I was listening to a phone in radio show this very morning when the guest speaker said he would make a phone call to a friend to clarify a point of interest. The radio host pointed out this would cause the studio to buzz and chirp because of his phone. So they aranged for his call to be made during a break. As to your speakers if they have a cross over network built in (stero two way) this will when the amp is off, short out the voice coil at these RF frequencies. Head phones do not have enough of a coil to resolve the phones signal. Try putting the amp on and without any source connected (set to aux) turn the volume up to a normal setting and bring your phone up to the amp. You should hear the data packets. Buzz.......Buzz.......Buzz.

Ok, that makes more sense. Thanks for clarifying that!

Nick

I am using a 3 watt 2 way radio. when i transmit within 500 mm of the pc monitor a buzz sound can be heard. it even does it when the computer is turned ofd.

i will check it tonight to make sure the sound is not from the speakers. They are permanently turned of.

What type of monitor?

It is a normal computer screen.

But i had a closer look at it last night, my speakers wasn't switched off after all and they were responsible for the noise even when turned down to zero. The stereo effect and old age deafness made me hear it in the screen.

The 3 watt is of the European class. But a 1/2 watt family radio transmitter manages a sound as well but not a tone.

Yes my cell phone does interfere on the speaker as well. Sometimes it seems to do that just before ringing.

It does not matter now you have found that it was the speakers after all. But I was not sure whether it was a flat screen or the old CRT type. Lets wrap this up for once and for all time. Cell phones (Digital) pulse the RF energy it is a switched Carrier wave form Packets of pulses are formed up so as to be able to be multiplexed in to a data stream, this means several phones can use the same frequency all at once. These data packets are then inter leaved the repetition rate is the 217Hz. The buzzing chirping is when these pulses produce a localised electro magnetic field this has a high field strength that is chopped on and off so producing an over all reduction in the mean level. The electronic circuits affected are reacting to an over load and the noise you hear is them complaining about this. It is like the impulse noise from an electronic ignition that is not suppressed. Car drives by you hear a ticking noise from your TV, radio, or the Hi Fi. Same as when a taxi or police car radio breaks through. The signal is often fed in via the speaker leads and then rectified and amplified. That's all folks.