hi adegee,
UPDATE ADOBE FLASH PLUGIN
based on the websites that you mentioned, im guessing that a common possible problem in them would be the flash plugin. If the flash plugin of your browser is damaged/corrupted, then its possible that its not playing the expected sound effects and music from flash videos/sound effects
i suggest you visit
http://www.adobe.com/support/flashplayer/downloads.html
then click on:
that should update your browser's flash plugin to the latest version
OR DOWNLOAD AND TRY GOOGLE CHROME
Google Chrome has its own integrated flash plugin. its worth a try if updating your browser's flash plugin does not work
simply browse to
http://www.google.com/chrome
====================
ALSO CHECK YOUR VOLUME CONTROL SETTINGS
For Windows 7 and Vista:
Click on the Speaker icon in the taskbar, click
Mixer
Turn up the volume for everything!
In this screenshot, the part of Firefox that handles volume control is called "
Plugin Container for Firefox". Raise up the volume bars, and be sure check that your youtube video inside the browser is not set to mute.
i hope this helps