Cellphone-type interference on speakers not caused by cellphone

[pex]

I have a speaker that performed the kind of beeping interference one gets when they have a cellphone near a speaker, that is receiving significant data.  The problem is that there was no speaker in the type of vicinity (that I am aware of) to cause the interference.

I'm not familiar with the reasons behind why the speaker generates the noise it does because of cellphone use.  Does anyone know what other interference might create this effect, or are the possibilities too numerous?  I normally do not have such random interference (otherwise this question would have been asked before.)

[majestouch]

Electromagnetic fields created by something like your mobile phone are very weak and won't effect the coil and magnet inside of a speaker in any audible way. If you hear some kind of interference from your speaker then what you're hearing is amplified interference. Interference from mobile phones just happens to be at frequencies that are easily picked up by the small circuits inside consumer electronics (due to the circuit trace lengths); the result is this interference is absorbed through these circuits and is then passed through the audio amplifier. So your cellphone needn't be next to the speaker, it just needs to be near the amplifier; or if it is next to your PC, the pre-amp in your soundcard.

With mobile phones, I have only experienced this with GSM handsets. CDMA handsets do not seem to cause much problem, which is probably due to the lower power spectral density of CDMA signaling (another topic).

[wheel83]

good answer lol

[pex]

(I certainly like it.)

The speaker at hand was a clock/radio/phone, which is in the same immediate area as my computer speakers and the tower.  I guess the computer speakers didn't create the sound even though they are on (but no sound is being sent to them.)  The radio was playing, however.

Normally I can judge the vicinity by which my cellphone affects the amp/speaker with this type of interference.  I don't recall the interference on my radio, but I don't recall that well.  The cellphone, while on, was at least three lengths outside the normal vicinity that affects the PC speakers.

I would figure the clock/radio/phone would be least shielded.  It's confusing but since I turned off the phone I believe I have had no further interference (it actually occurred once or twice more since I posted prior to that change.)

Thanks for the explanation.