Cell Phone and Speaker Noise

[arrosen]

Why do my speakers (car, computer, etc.) make "staticky" (but rhythmic) moises every so often when my cell phone is near them?

[Missy2U]

Nextel phone? Simple answer (VERY simple - I got this from someone who does know what they're talking about, but they had to dumb the answer down for me so I could post it ) is that the frequency your phone is transmitting at is causing the interference with the other electronics.

[arrosen]

Originally Posted by Missy2U

Nextel phone? Simple answer (VERY simple - I got this from someone who does know what they're talking about, but they had to dumb the answer down for me so I could post it ) is that the frequency your phone is transmitting at is causing the interference with the other electronics.

Cingular...Tyanks for the answer. I wonder if there is a way to change it...it is quite annoying!

[TellMeI'mNotCrazy]

It generally happens when your phone is actively communicating with the tower. I used to "amaze" my mother by telling her I had a phone call before the phone even rang, because of the static on my computer speakers. Then she figured it out of course, and will yell for me as soon as the speakers start buzzing. Also, the tower sends out intermittent "Where are you" signals (actually, I am not very strong on this, I tend to think they're more "Who's here in my area" from the cell tower rather than a specific "Where is mobile phone XYZ?").

Can also make your monitor or TV flicker, among other things. The only way I know of for stopping it is either keeping your phone turned off, or keeping away from speakers and such. I know, not so easy to do in a car.

[GargoyleWB]

I also have an old Sony Discman that is sensitive to cellphones (it is very annoying if my phone is anywhere nearby), also my old-school desktop telephone will chatter if my cell phone is nearby.

[James Westphal]

Originally Posted by Missy2U

Simple answer the frequency your phone is transmitting at is causing the interference with the other electronics.

This is fairly obvious - the question is why.

[Philster]

I find that Nextel phones cause interference before ringing and when they drop/pickup weak signals. In strong areas, intereference isn't an issue. In/Out signals are the worst interference sources.

[CJJ*]

Originally Posted by James Westphal

This is fairly obvious - the question is why.

Nextel iDEN phones and GSM-based phones such as those provided by Cingular/ATT follow a TDMA modulation scheme, i.e. timeslots are assigned to each transmitter on a particular frequency to broadcast digital data, allowing for multiple users on the same frequency. Because of this, the transmitter turns on and off repeatedly (~67 times a second?) during a call to broadcast during the assigned timeslot. This is what you are hearing. There is speculation that GSM phones produce less interference because they operate at higher frequencies, but I believe any difference is minimal.

CDMA phones broadcast continuously, relying on division over RF carriers rather than timeslot, so they do not produce the interference.

[engineer_comp_geek]

Originally Posted by James Westphal

This is fairly obvious - the question is why.

Here's a previous thread with a bit of info in it:
http://boards.straightdope.com/sdmb/...d.php?t=302957