I Got This Fixed . Checkout How i did That .. Thanks IFIXIT
Source- [http://bit.ly/2niZM7J|Fix Acer Laptop Sound Problems]
* Restart Your Laptop And Unisnatll The Sound Driver .
* Go to the Acer Website and download to the latest sound driver .
* install the driver and restart the computer
* check the sound key and settings too
See If This Helps to fix the sound Problems
Good luck