Hi, I have a theory. It could be the frequency of your Wifi signal, when you increase the volume of your speakers it becomes susceptible to higher frequencies. I believe you are using 5Ghz ? Its recommended to use 2.4Ghz Apart from this there is no connection between your speakers and Wifi.
Hi! I have a annoying problem with my Dell L702x i5-2430M @ 2.4 and  Intel Centrino Advanced-N 6230. When I reach high downloading speeds (4-9mb/s) and have music on ( laptop speakers, using media player classic build version 1.5.2.3456) I hear some intense crackling sound from the speakers, but only when the music is on, whenever I pause the music the crackling stops. If I stop my downloads then the crackling sound dissapears. Any idea what the cause of this is? Thanks! 
Crackling sound when Downloading at high speeds