When streaming and recording, having selected the wrong file format as output and having multiple tracks can make sound "disappear". If you select box "2" for "Mic" then what you hear from the desktop or game will be recorded on the first track and what you say through the microphone will be recorded on a second track. So if you select for both "Mic" and "Desktop Audio" box "1" then both of the audio will be merged into one track. The "Track" boxes determine on which audio track the sound, coming from the selected device, is to be recorded on. Lastly, uncheck every "Track" box of both "Mic" and "Desktop Audio" except "Track" box "1" (see advancedAudio.png below) So you basically tell OBS what the stream/video should record and what should be heard only by you or the stream/video. "Output" means the sound that will be heard in the stream or video. "Monitor" means the sound that you hear through your headphone or speaker. In this drop down menu you have "Monitor off", "Monitor only (mute output)" and "Monitor and Output". Then for you "Mic" and "Desktop Audio" select "Monitor off" under the "Monitoring" tab. Here you can find a little bit more advanced audio settings and tools that you can play with to optimize your recorded audio from the selected devices and/or added mediasources, which can be music files or videos. Right click on the settings icon of any audio track in the "Mixer" box and click on "Advanced Audio Properties" (see RMB.png below). If your sound goes through your headphones but you have selected speakers in the OBS settings then it will record nothing, as there is no sound being transmitted to the speakers. You basically tell OBS which devices are to be recorded. This is a common mistake that users make when regularly switching between headphones and speakers. Make sure you have selected the correct output and input devices in OBS "Settings" => "Audio" (see audio.png below).