Hi David,
Thank you for posting your problem and sharing your effort in performing updating the drivers. May i know what is the Model of your Surface Laptop.
Lets try this possible this might help us to fix your sound problem on your Surface Laptop.
Please try this method.
On your Surface Laptop screen go to system tray near the date and time. Right click the speaker icon then choose Troubleshoot sound problem. This will open another window and start the get help app that will scan and fix the issue.
Let me know how this goes. If you need more help please feel free to let me know.
Best regards,
Jansher