Yesterday when I used Chrome to watch videos on YouTube, there was no sound in my laptop. After looking into this issue, there is no issue with my sound card because I can still use IE9 to watch videos with the clear sound. What happened to Chrome? Finally, I find the main issue is from Shockware Flash.
How to fix the sound issue in Chrome?
Go to Chrome Plugins
Disable Shockware Flash (11.7.700.179)
Go to YouTube again
Click the video and it can lead you to install the version (11.7.700.169)
After that, sound is working in Chrome.