No sound when plugging Apple TV into a TV/monitor using a DVI/HDMI converter cable.

I have a TV/monitor that I am trying to use my Apple TV with. I had to purchase a DVI-D to HDMI cable to hook to the TV because it did not have a HDMI port. Now that I did this, I do have a picture but no audio. Is there another cable I need to get audio? Or is there another DVI-HDMI cable I should be using? I have already been to Best Buy twice trying to get this to work so any help would be greatly appreciated!!

When I had cable, I could use the TV/monitor when plugged into my DVR so I know it has audio capabilities.