DVI does not support audio, regardless of what computer you're using. If you are using DVI, you need to run the audio separately, either directly to your TV or through one of the adapters that combines a DVI and audio signal into a single HDMI output.
If your MacBook has a mini-DisplayPort output, then depending on the model of MacBook you have, that may support both audio and video with the appropriate mini-DisplayPort to HDMI adapter.
I was just wondering about this very thing; I have a MacBook7,1 (purchased Dec 2010) and want to hook it up to my flat screen HDTV and was wondering if I needed to buy a separate audio cable.
I read that now MBP have the audio through the MDP; however, if I understand correctly this does not extend to plain vanilla MB7,1.
Would someone be kind enough to confirm this statement. Thank you 🙂