Case update, Dell SupportAssist was used to update the system to the latest drivers. After the updates were completed this resolved the issue.   Dell SupportAssist can be downloaded from here    
Two days ago, after working fine since purchase a couple of years ago, the internal microphone just stopped working, and has disappeared from the list of input devices. There is nothing to troubleshoot as it literally has disappeared. This is *incredibly* disruptive if you rely on your laptop for calls and online meetings, which I do - I've had to cancel/leave a couple of pretty important calls which is really embarrassing. I understand that there is some sort of roll-back fix to a previous driver that may work for this - can I get a step-by-step for how to do this please, I don't want to cause more issues just having a go myself, and I urgently need to be back on line for this. Thanks  
Inspiron 7591 2n1 Microphone disappeared