This is a rather well-known phenomena, to the extent that I was once advised, when going back-stage in a theatre, not to bring my mobile phone lest it set the t

This is a rather well-known phenomena, to the extent that I was once advised, when going back-stage in a theatre, not to bring my mobile phone lest it set the theatre's sound system buzzing. It's caused by the periodic nature of the data frames in the original GSM protocol[1]. Judging by the existence of academic research from 2005 into mitigations[2], I'd venture a guess that it has been fixed in the more recent protocol revisions and so is no longer as common (which matches my own experience in any case). [1]: https://electronics.stackexchange.com/questions/39127/why-do-my-speakers-make-a-noise-when-my-cell-phone-gets-a-call https://electronics.stackexchange.com/questions/39127/why-do... [2]: https://www.diva-portal.org/smash/get/diva2:836430/FULLTEXT01.pdf https://www.diva-portal.org/smash/get/diva2:836430/FULLTEXT0...