Cell phone interference

[yin7yang64]

Hello, 2011! Here's a tech problem that could only occur in the age of the iPhone. I've been running a Digi002 based home studio in my condo building for years. About a month or two ago I started hearing the stuttering digital audio signature that I've come to associate with an iPhone in operation coming through my active monitors. I thought it was simply a nuisance 'til I discovered it was sometimes showing up in my recorded audio, too. The system is grounded via a three prong AC plug. But are there other solutions to prevent this noise from being an ongoing occurrence? I think it must be a neighbor with a new iPhone because the same sound has cropped up at music rehearsals when a keyboard started picking up the same digital chattering and it seemed to be related to the keyboard player's iPhone. (I suppose 4G iPads may cause the same interference, too.)

Any suggestions?

[Craig F]

best I can tell is the switch mode power supplies used in everything these days are very susceptible to the GMS carrier frequencies

heavy RF shielding of you room is probably your only option

[nedorama]

For shows, we make all bandmembers switch their smartphones to Airplane mode to avoid this sound.

Older guitar amps are especially susceptible to this noise, as are unbalanced lines.

How much of your studio is on unbalanced cables? I have my music studio in the same room as 2 iphones, and with everything balanced, no noise.

[zoff]

The cell phone noise is generated by the power supply in the phone. You can use anti static bags, such as the ones that memory sticks come packaged in, to block the noise. Just sit the phone over the bag. AFAIK the noise is only generated when the phone looses 3g and switches to EDGE (the older slower but more ubiquitous data transmission). This is not an iPhone only issue, any GSM phone that switches to EDGE will do it.

[yin7yang64]

Originally Posted by nedorama

For shows, we make all bandmembers switch their smartphones to Airplane mode to avoid this sound.

Older guitar amps are especially susceptible to this noise, as are unbalanced lines.

How much of your studio is on unbalanced cables? I have my music studio in the same room as 2 iphones, and with everything balanced, no noise.

My studio is a project studio for radio and audio production. The mic cable is balanced but the output from my dbx 286A preamp is only a 1/4". The outputs to the active monitors are unbalanced. I could certainly replace them with balanced cable that's grounded at one end.

[zoff]

Originally Posted by yin7yang64

My studio is a project studio for radio and audio production. The mic cable is balanced but the output from my dbx 286A preamp is only a 1/4". The outputs to the active monitors are unbalanced. I could certainly replace them with balanced cable that's grounded at one end.

Balanced cables will not help, you have to shield the phones as I stated above. AFAIK The above poster doesn't have problems with his cell phones because he probably has a strong 3G signal and the phone doesn't have to switch to EDGE.

nedorama turn off the 3G in your iPhones if you don't believe me. Settings>General>Network>Enable 3G: OFF

[MRausch]

Also, if you find yourself screwed over by previously recorded noise, check out the Izotope RX plugs.. they do a good job of getting it out.

[BRH]

Kill neighbor with iphone.

[zoff]

Originally Posted by BRH

Kill neighbor with iphone.

...or to be kinder and gentler, you could try anti static film on the wall next to your gear. I know the film works when put up against the back of a phone, but don't know if it will work on the wall. I've never heard the noise radiate more than 8 feet, this is NOT RF noise, it is noise generated by the phone's (NOT only iPhones) power supply when using EDGE.

[Noiselab]

I have heard this same phenomenon with any AT&T phone held within about 2 meters of our Polycom conferencing phone - not just iPhones. It happens whenever an AT&T network phone is receiving either an SMS, an e-mail or an in-bound call via either 3G or EDGE/GSM - but I've never seen it be an issue when farther than 2 meters or as bad with phones on other carrier networks. Balanced lines are not impervious if the cell phone is within about a foot or two.

It happens in my project studio as well and is the source of my "cell phones off" rule. I did have a 3G iPad which also created the same issue, so I traded it to the wife for her wifi-only version.

If the "2 meter" observation is correct, I'd be curious if you share an exterior wall with a neighbor. If so, rotating your setup to a non-shared wall might help.

NL