Tinnitus is a medical term used to describe a ringing or buzzing noise that people can hear permanently in one ear, both ears or in the head.

BBC: Fears that music volume limits 'could be ignored'

Ask attendees who are not dialing in on a cell phone to place their cell phones on mute and keep them away from the telephone, as this can cause a loud buzzing noise.

FORBES: Career Boot Camp: 5 Tips To Lead Effective Conference Calls