Sound distortion has developed while listening to a DVD or using Skype
Because I do not know your particular computer in detail, I will answer generically.
Because of the complexity of design where the interaction between software drivers and the hardware are very inter-dependent, it is difficult to determine the fault directly. I would suggest to uninstall the sound card drivers using the device properties manager, re-start the computer, and let it re-install them. If they do not auto install, then do it manually using the respective installation source location.
You can also try downloading the sound drivers directly from the Acer site and re-installing them, or from the respective sound card (chipset) manufacture to see if this fixes the fault.
I am assuming you tried listing to the sound using several headsets or external speakers to test it. I know of cases where a person was complaining about distorted sound from their computer. It turned out to be the speakers were defective and not the computer.