However, many people are experiencing microphone issues in Gmail. The telephone rings and you can hear the other person. However, the receiver is unable to hear your voice. Many Gmail users are experiencing the same problem. This occurs because Gmail is unable to detect the correct microphone of your computer. This can be fixed by changing Chat setting in Gmail:
1) Log on to Gmail and click on Settings at the top right.
2) Under Settings click on Chat.
3) In voice and Video chat you can find Microphone. If the microphone has been set to Default device, change it with your microphone name.
4) Save the settings and you the microphone problem will be solve.
Try to call phone from Gmail and the other person will be able to hear you.