I’ve managed to fix it, and it actually seems to be a microphone issue. Go to System Preferences -> Sound, select the Input tab and set Internal Microphone as the input (mine was set with my headphones’).
Crappy sound goes way after that =)
EDIT (May 30 2018):
I’ve found out an easier way to do the same as above. Instead of opening the System Preferences, you can just go to the Mac OSX toolbar, press Option (alt) + click on the sound icon and then select “Internal Microphone” from the “Input Device” list. Print screen as follows.
