Currently Being ModeratedNov 9, 2012 2:23 AM (in response to musicalbox23)
When you say the volume jumps to +6 dB, do you mean the signal, or does the fader actually move?
Also, what happens if you do not have an audio channel selected?
What happens if you set the selected audio channel to "no input"?
Fact is cell phones give relatively powerful electromagnetical pulses (they're transmitters after all) that will interfere with (or better: be received by) the electronics in your audio chain. Apart from rigorously electromagnetically sealing off all your equipment (faraday cages), I think the best action is as you've done: ban cellphones.
You could set up a second (-hand?) Mac (mini?) for communications: email, web, skype, facetime and anything else not directly related to music.