There are certain random issues with audio in Chrome/Flash since 10.8.4- one solution I've found is to use the older patched AppleHDAs from MultiBeast 5.4.3. The AppleHDA version is 2.3.7. Current AppleHDA is 2.6.0.

Here's a list of versions of AppleHDA since 10.7:



Hope this helps.

Older MultiBeast revisions can be found in the MultiBeast Archive:
http://www.tonymacx86.com/downloads.php?do=cat&id=6