When I add a YouTube layer, ManyCam starts the audio. It is normal. But when I mute layer pushing the speaker icon on the upper right corner of that layer or by selecting “mute layer” in the popup menu, nothing happens. the sound is going on.
I reinstalled manycam, tried several (different) YouTube streams, used a different webcam for my own camera layer with no success. The noise is still going on.
Are you on Mac or PC What version of ManyCam is installed? Please also post a screenshot of what you did to mute the layer. Does muting global sound work for you?
Mac OS 11.1 (Big Sur); All sound is switched off (see attached screenshot). Neither global sound switch nor the layer sound switch has any effect. The youtube layer keeps playing sound.
I have removed and installed the software again from the link given by the ManyCam support, but no change.
I have tried all features aiming to mute a layer or the whole audio output of manycam, with no success. This was the first. 
Nothing has changed.
I could manage the whole problem by using my mic (instead of manycam sound output), BUT in this case I hear the sound and people on the other end of the line also hear that when I am not muted, because my microphone reads it from the speaker (from the atmosphere of the room). If I use headset the only problem is that I hear the sound… and it is pretty a problem when you present to an audience. They will hear only you but you hear a loud music if the youtube channel is “featured” with some music (eg. https://youtu.be/K_Vg94nBiaY). If I want my background the Rialto Bridge, I can do it only with the background music.
You should develop a switch to cut the connection between the audio system of OS X and the ManyCam application.
