When you browse to Skype for Business meeting using Chrome, and it will prompt you the following screen to start Skype for Business App.
In some cases, your meeting start without audio after it has started.
This what you need to do.
Right click on the speaker at your taskbar. Choose Sounds.
Go to the Playback tab to configure your audio device. You must have the green tick at your audio device in order to have sound for your Skype for Business App.
You should have 2 Skype Meeting App in your Volume Mixer.