HI,
Just to make sure, open System Preferences/Sound and make sure your sound isn't muted.
Also, try deleting this file.
com.apple.soundpref.plist
/Users/YourName/Library/Preferences.
Drag that file from the Preferences folder to the Trash, empty the Trash and restart your Mac.
Also, try repairing disk permissions.
Quit any open applications/programs. Launch Disk Utility. (Applications/Utilities) Select MacintoshHD in the panel on the left, select the FirstAid tab. Click: Repair Disk Permissions. When it's finished from the Menu Bar, Quit Disk Utility and restart your Mac. If you see a long list of "messages" in the permissions window, it's ok. That can be ignored. As long as you see, "Permissions Repair Complete" when it's finished... you're done. Quit Disk Utility and restart your Mac.
Carolyn 🙂