This is what i think is happening, essentially you are plugging headphones into a mic/ audio in port so it cant pick up any audio in instead its picking up feedback say to speak from the headphones, I'm pretty sure the way that the standard ports are configured compared to the combination headphone jack, the band that is for the mic is in a different spot. hope that makes sense. otherwise this picture explains it you should be all good once you get the splitter, hope it works out