Skype Audio Settings
Check what the Skype audio settings are set to ensure that your speakers and microphone are working properly
Open Skype for Business
Click on the Settings button
Go to the Audio tab on the left
If you have a headset, Skype will choose that, otherwise, choose Custom Device from the dropdown
If you’ve chosen Custom Device:
Ensure that your speaker is not a monitor. You can change the speaker by clicking on it and selecting from the dropdown list
Ensure that it sees a microphone and that when you talk it can hear you. The blue bar by the microphone will move if it can hear you.
Click OK to save your changes.