Problem with voice auto play and other sound effects
Excuse me, the voice auto play and other sound effects of duolingo are not working. My PC speakers are working very well. I couldn't figure out the what's the fault. Please fix it as soon as possible.
Try the following:
reload the page (Press F5)
try another browser (e.g. if you use Firefox try Chrome and vice versa)
check if sound works on other websites, e.g. Youtube
reboot your PC (maybe some plugin just crashed in the background without you noticing)
I had the problem a few times, reloading the page was almost always the solution.