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Speakers beeping due to mobile phone

by MichaelW24
Tags: beeping, mobile, phone, speakers
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MichaelW24
#1
Nov21-05, 11:38 AM
P: 21
Can anyone explain why I get a beeping noise on my speakers when I am about to get a phone call on my mobile phone? Just something that I've become used to, but I realised I don't actually have a clue how it works, and am quite interested.

Thanks for any help!

Michael
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xPAGANx
#2
Nov21-05, 03:54 PM
P: 50
It is very common to get interference from cell phones on your speakers. Move your phone away or just accept it.
MichaelW24
#3
Nov21-05, 05:07 PM
P: 21
Thanks for your help, but I have already gotten used to it.

I was just asking how it works, not checking that it does.

-Job-
#4
Nov21-05, 06:00 PM
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Speakers beeping due to mobile phone

The same thing happens to me. My speakers have some other abilities as well, like playing the actual conversations of people on cell phones. One time in the middle of the night they played a bit of a conversation in spanish which i assumed they must've picked up from a cell phone. They also make constant white noise while plugged in. I bought them at Staples. Let me just go on a tangent here, Staples sucks. I bought two items from them that happened to be damaged. I'm pretty sure that if someone returns something there because it desn't work properly they just put it right back on the shelf.
Psi 5
#5
Nov21-05, 06:22 PM
P: 113
Just guessing here but I would say that somewhere in the amplifier or before, something is acting like an antenna and picking up the radio waves and amplifying them so you hear a sound at the speaker. If it was after the amp stage it wouldn't be too loud and computer speaker wires are usually coax which would probably reject the radio signals. I could be wrong. I know that when I turn on my cell phone I can hear a series of beeps in my computer speakers even if the computer is off because the amp stays on when the computer is off.
vanesch
#6
Nov22-05, 01:11 AM
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It is an effect of the non-linearity of the first stages of the amplifier. What actually happens is that when high-frequency signals are seen by the entrance of the audio amplifier, the amplifier cannot follow the very high oscillations. Normally, you'd say, don't worry, that means it gets filtered out. That is correct if the entire system is linear. But the signals from a cellular phone are MODULATED high-frequency, and due to small non-linearities in the amplifier, you change slightly the operating point because of the incoming signal. Now, that, in itself would not be a problem, but the movement of the operating point follows the modulation (it moves, say, slightly up when the signal is present, and moves down again when the signal is not present). And as such, the modulation signal becomes amplified.

It is exactly the same principle as an old AM radio, where you use a (non-linear) diode to "detect" the modulation. Given the rather high power a cellular phone uses for his broadcasts, this is seen by the audio amplifier. Any AM radiostation nearby would do the same. FM wouldn't because the envelope is at almost constant level.
essaywriting
#7
Feb17-10, 04:18 AM
P: 5
its Waves or frequency that reflect against speakers

it wont beeps unless you get call or searching for network
rcgldr
#8
Feb17-10, 06:09 AM
HW Helper
P: 7,033
Something to do with the amplifier stage. It happens in my wife's car even with the stereo off, so I'm not sure how that happens, since I assume there are capacitors involved in the final amplication stage. It doesn't happen in my car though. At home, my monitor gets messed up if a nearby cell phone goes active. I have CRT monitor, but I'm not sure if it's affecting something inside the monitor or affecting something inside the video card or the vga cable (I have the sides of my case removed, which reduces the shielding).
Jobrag
#9
Feb17-10, 11:53 AM
P: 475
I'm sure that all these answers are correct but I'm not sure that they amswer the question. When your mobile phone is called the network sends out a "where are you?" signal, your phone answers as loudly as it can "I'm here" it is that signal that you here on your speakers. Part of the rationale of banning mobile phones om aircraft is that this srong signal might interfere with flight systems. I used to own a waterproof electric razor that if placed by my mobile would turn itself on if someone called the phone.
MATLABdude
#10
Feb23-10, 04:35 AM
Sci Advisor
P: 1,724
This seems to only happen with GSM phones. A friend of mine speculated that it was due to the low frequency signal piggybacking on the high frequency carrier, which then got low passed and converted to the familiar sound that starts with the long and then changes to short pulses. It's fun because it precedes the actual cell phone ringing by a few seconds.
Ouabache
#11
Mar1-10, 11:29 PM
Sci Advisor
HW Helper
P: 1,326
Quote Quote by -Job- View Post
The same thing happens to me. My speakers have some other abilities as well, like playing the actual conversations of people on cell phones. One time in the middle of the night they played a bit of a conversation in spanish which i assumed they must've picked up from a cell phone.
This is related but you cannot make the assumption, it is originating from a cell phone. It also sounds like your cell phone is not necessarily near the speakers of even powered up. The audio signals could be coming from a standard cordless phone that also transmits RF.
The more recent models use bandwidth at 1.9, 2.4 and 5.8GHz. The wires to your speakers can behave as an antenna, pick up these RF (modulated voice) and play them out your speakers, as described above for cell phone transmissions.


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