I'm running a white macbook OS X 10.5. I just plugged my headphones in to sit back and listen to some music when the guy next to me asked if I'd turn down my speakers. I'm thinking how can he hear my headphones?! Turns out my audio is playing through both my built in speakers and my headphones at the same time... How is this even possible? I thought the sound cards on these laptops are one way? I've gone into my system settings > Sound > Output and can see that when I plug in my headphones the output changes from internal speakers to headphones. So how can I change this so just my headphones are the only output?