Just gonna blast you with potential fixes, hope one of these works.
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Fix:
Right Click on "Speakers and Headphones" > Playback Devices
Playback Tab
Make "Speakers and Dual Headphones" the default.
Disable "Independent Dual Headphones"
Disable "SPDIF (Digital out via HP Dock)"
Recording Tab
Make "External Mic" default
Disable "Integrated Microphone Array"
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try the following fix: Right-click the speaker icon in the system tray (alternatively, open the Sound settings from your Control Panel) and go to Playback Devices. Set your Default Playback Device to the desired output (headphones), and disable any assigned Default Communications Device.
For other potential fixes, hit up this resource:
http://sea.battle.net/sc2/en/forum/topic/126112640If you have continued problems let me know and I can do some further searching.