To mute or unmute the system volume, you can simulate the Mute key press using the WshShell.SendKeys method:

var oShell = new ActiveXObject(WScript.Shell);

oShell.SendKeys(Chr(&HAD));

As for changing the volume level from a script, there's a solution that involves some Windows automation, such as launching the System Volume applet and simulating the appropriate keyboard shortcuts in it, but I don't think it's reliable. Therefore I recommend that you use some external utility capable of changing the volume level, and call it from your script. For example, you could use the free NirCmd tool:

var oShell = new ActiveXObject(WScript.Shell);



// Increase the system volume by 20000 units (out of 65535)

oShell.Run(nircmd.exe changesysvolume 20000);



// Decrease the system volume by 5000 units

oShell.Run(nircmd.exe changesysvolume -5000);

NirCmd can also mute or unmute the system volume:

var oShell = new ActiveXObject(WScript.Shell);

oShell.Run(nircmd.exe mutesysvolume 0);  // unmute

oShell.Run(nircmd.exe mutesysvolume 1);  // mute

oShell.Run(nircmd.exe mutesysvolume 2);  // switch between mute and unmute