Sound clicking with Dell Latitude E7450 and doking station (advanced)

Hello,

I encounter a strange behaviour with my new Dell E7450 and my docking station (advanced).

I have my laptop plugged on my docking station and my speakers connected on it too. When I play music or system sound I hear a low "click" just before the sound comes (like the first sound you hear when you plug your jack in an equipment).

When I plug my speakers directly to my laptop, everything works fine and no "click" occurs. I try to update my drivers but nothing change !

Any suggestion or idea ? I try my laptop on antother new docking but same behaviour.

Thanks for your help