Kanex Mini DisplayPort to HDMI Adapter doesn't play audio on Sony Bravia TV
Some thoughts, and things for you to check on:


What model of MacBook Pro do you have? Older ones (pre-Mid 2010) don't have audio out through the Mini DisplayPort.
Have you tried looking at System Preferences » Sound  » Output? What devices are displayed, and what have you chosen?
Can you explain what "I have an audio that connects the Mac to the PC in HDMI Audio jack" means?
Which Mini DisplayPort to HDMI adapter do you have? The early models were made to work with the then-current MacBooks (and Pros)—and as those models didn't have audio out over Mini DisplayPort, there wasn't any reason for the cable to, either.
Have you tried hooking up a cable from the Mac's audio out/speaker jack directly into the TV?
Some possibly-helpful info:


Can I output video to my TV using a MacBook Pro? (Apple.SE)
About Mini DisplayPort to HDMI adapters (Apple.com)
Apple Mini DisplayPort adapters: Frequently asked questions (Apple.com)