I use Macbook Air (early 2014) running on OSX Yosemite 10.10.5 and this is the only thing that worked for me among all the solutions posted. I'm so delighted!
Triple-click anywhere in the line below on this page to select it:
/Library/Preferences/Audio
Right-click or control-click the highlighted line and select
Services ▹ Reveal in Finder (or just Reveal)
from the contextual menu.* A folder should open with an item selected. Move the selected item to the Trash. You may be prompted for your administrator login password. Restart the computer and empty the Trash. Recreate your settings in the Sound preference pane.
Original post link here: https://discussions.apple.com/thread/7101870?answerId=28470363022#28470363022