If the problem dissapears with headsets then it sounds like it is feedback. Maybe someone has the mic gain turned up too high or a speaker is too close to the mike. You'll need to experment but it could be any one of you who has the problem.
This thread is now locked and can not be replied to.
Best phone camera 2016/2017: Galaxy S7 vs iPhone 7 vs Google Pixel vs HTC 10 Evo vs OnePlus 3T vs…
1995-2015: How technology has changed the world in 20 years
These are the Best Christmas Ads and Studio Projects of 2016
Super Mario Run preview | Hands-on first impressions of Super Mario Run: Mario's iPhone & iPad…