I've been using two Sena 20S devices since July of 2015 with great sucess.  In Feb of 2016 I upgraded the firmware to v1.6 (from v1.41) and continued to have a wonderful experience with the 20S devices.  Was living in Des Moines Iowa then, and had no noise issues during HD intercom operations [to my other 20S only; no group experiences at all].  Moved to Springfield MO over the winter and this spring I've had ever increasing trouble with static and popping noises during intercom use [on the initiating device only; hardly any on the paired device].  My last ride it got so  bad I had to terminate intercom mode.  I just upgraded the firmware to v1.7.2 and I hope that solves the problem.  I'll re-post soon & let you know.