This is a good subject (assuming you're talking about electronic signal interference issues). It has come up in the past.
Let me share a personal anecdotal story on this : One time I had corded earbuds under my full cup md'ing headphones. The little earpods are left to be loose inside the larger cups, so that I can hear my phone ring. And there's enough volume that the little buds do not need to be inside the ear canal. So I can stop, at any time, and take a phone call. And not have to even raise the phone to my head. I just click the "answer" button, and I'm already wired.
So One time I was detecting a park for deep-silver-cherry picking, and my wife called me. I answered her call, and she began yapping about something on and on and on. So I figured that since I had both the cell phone AND the detector on independent audio, that I could continue to detect WHILE talking to her. And after a minute or so, I got a very iffy signal. Difficult to isolate, judge, etc... But just enough audio clue that I made a mental note that, after this call is over, I'm going to check this one out more.
A minute or so later, the call ended, and I began to criss-cross swing over the flagged spot . And I noticed something interesting : The signal CLEANED UP BETTER. I was able to get a better TID, more consistent, etc....
Which led me to wonder if : While I am an active phone call, is there some sort of cross-talk that was actively subtly affecting the detector ?? I ran this past a tech friend of mine (who works with 'puters as related to cell-phones). And he told me that, actually, our phones are PERPETUALLY "talking" with the cell towers around us. Sending and receiving signals. So that the phone is "seeking out" to find the nearest towers, AT ALL TIMES. So his notion was that if I thought there was interference in an actual active call, that so too will some level of interference be there with the phone simply carried on your person.
However, I carry my phone, in the powered on position, all the time. I have never experimented with turning it on and off, over a flagged iffy/deepy, to see if there's a difference. Any tech people here to chime in on this subject ?