XPS 13 (L322x) - constant speaker noise after upgrading to Windows 10

Hello,

today I upgraded my XPS 13 (L332x) to Windows 10, with no problem - almost. Ever since the upgrade, when I want to listen to any kind of sound using the built-in speakers, I get a very loud constant noise. It is VERY annoying and it lasts for a while before the noise suddenly dies. The noise immediately comes back as soon as there is another sound, e.g. a system sound. Also the noise louder than e.g. the music I want to listen to.

Interestingly when I use headphones, there is absolutely no problem - the sound is clear as always. 

I did not have the same problem when running Windows 7.

I have updated all drivers to Windows 10, in particular the Audio, Video, Chipset and Touchpad drivers. Also I am using the latest BIOS.

Any help, anyone?

Best, C.