Audio on tv will not work when I have vga cable connected

Hello, I ordered a vga cable with the audio attatchment with it. I have it plugged in and I am getting picture on my tv, but no sound from the movies trying to play except on my computer speakers. I hear a quiet buzzing sound in my tv speakers when connected, but everything I try and play has no sound. And when I connect and disconnect the audio cable it makes a noise on the tv speakers. I have no clue what I am doing wrong. Someone please help, I am about ready to throw my computer across the room!