Today a microphone has some noise.
    

So please switch off your microphones and switch them on only when you talk.
You can click on & off the Mic Icon to speak (All computer types) 

active mic   

Or

(Windows)hold down your computer's [Ctrl] key when speaking (release it to stop).

(Mac)hold down your computer's [F2] key when speaking (release it to stop).

control button