Mute Alerts when on a Skype call

Hello,

 

Is there any possibility of muting alerts (ie email alert sounds or IM sounds) or setting calls to come through as silent when already on a call? I understand setting your Skype to busy will help with Skype - Skype calls but if someone is calling from a regular phone or mobile the call will ring through without them realising you are on another call. 

I have attempted to do this within the Windows Communications tab however it does not affect anything when on a Skype call.

 

Thank you.