Buzzing on GSM audio

Joerg Reisenweber joerg at
Sat Jul 26 06:02:39 CEST 2008

Am Sa  26. Juli 2008 schrieb Dave Clark:
> Jim Morris wrote:
> > Dave Clark wrote:
> >
> >   
> >> Can you correlate the buzzing to your signal level?  IIRC, most phones 
> >> will increase transmit power as needed to overcome noise.  If the noise 
> >> is caused by RFI from the GSM radio, increased power would tend to 
> >> increase the interference.
> >>     
> >
> > I have a very low signal here one bar at most, I haven't tried it where 
there is good reception, as 
> > I can't really use it as a phone yet. However with that clue I'll try it 
ASAP in an area where I get 
> > better reception.
> >
> > FWIW my other Cell phones also get very low reception here, but don't have 
any noise.
> >
> > I hope if this is a H/W problem we can get it fixed even after the 
warranty expires as it definitely 
> > makes the phone a brick otherwise.
> >   
> I know GSM transmissions can present significant interference on audio 
> equipment - if my phone (any GSM phone) is on my desk, I can hear 
> periodic static in my computer speakers as the phone "checks in" with 
> the cell tower - it sounds like three quick, buzzes in about 1 second. 
> This happens a couple times an hour.
> When it receives a call, I get a steady buzz starting 1 to 3 seconds 
> before the phone rings, and continuing until I hang up.
> I would imagine that ALL cell phone hardware would have to deal with 
> this audio interference, and since I don't hear it in many other phones, 
> I'm pretty sure it can be filtered out with some sort of audio processing.

Nope, it has to be stopped on RF-side, before even entering audio-path. For 
this we have to spot the exact way RF is entering back to the device. That's 
what we're about to do.

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