The Late 2008 model 5,1 Aluminum Unibody and the Late 2009 model 6,1 and Mid 2010 model 7,1 White Unibody have a Mini DisplayPort. The Early 2006 model 1,1 through Early 2008 model 4,1s plus the Early and Mid 2009 model 5,2s have Mini-DVI ports.
The Mini-DVI to HDMI doesn't carry audio. If you connect the MacBook using a Mini-DVI to HDMI adapter you will probably need to use external speakers or a 3.5mm stereo headphone jack to RCA sound plugs connected to a stereo system for audio if your TV doesn't have separate RCA input plugs or a 3.5mm stereo input plug for audio with the HDMI plug.
The Mini DisplayPort to HDMI doesn't carry audio unless you have the Mid 2010 model 7,1 and there're no audio plugs on most TVs to work with HDMI since it's expecting audio with the HDMI. Check your TV manual to see if it has audio plugs that work with one of the HDMI ports.
If you have the Late 2008 model 5,1 Aluminum Unibody or Late 2009 model 6,1 White Unibody with the Mini DisplayPort rather than the Mini-DVI there is an adapter that uses the Mini DisplayPort and a USB port to combine video and audio to HDMI. It's only 2 channel stereo not 5.1 Dolby Surround.