This was first reported a while back by early adopters using beta releases, but it still seems to randomly happen even with installing the latest releases of OS X Yosemite on a wide variety of Macs.
Occasionally, the same situation occurs randomly after installing an update to OS X 10.10.x as well.
A few Mac users that update to Mac OS X discover their sound and audio output has ceased to work, leading to a completely mute Mac that does not respond to the volume keys.
Interestingly enough, the reverse situation also can occur, where a Mac is connected to a TV and there is seemingly no audio output, at least until HDMI has been selected as the proper sound output channel.
Just remember if you experience this, it’s no cause for panic, it’s a simple fix.
Double-click on the "Splashtop_Streamer_Mac_vx.x.x.x.dmg" file. (The file name will vary depending on the version downloaded.)3. If a warning message appears, click "Open" in the message box.5.
An updated audio driver might resolve the problem if the computer is experiencing sound problems after upgrading the operating system to Windows 8, or the computer is experiencing sound problems in a particular software program.
Input the user password to continue the Running if system requests it.6. Confirm that the Streamer is removed completely (the Splashtop Streamer icon no longer exists in the Launch Pad).
Microsoft has confirmed that after installing certain updates, some Windows 8.1 users had problems with sound on their computers.