In this thread
Icedragon posted another workaround. Maybe this can help you.
If i turn any of the sliders down, i get echo when people are talking, my wourkaround now is to set all the sliders to max and then use the windows soundmixer to lower it.
Edit: Tested it and went for caves, then I teleported myself back to the first town. Icedragon's workaround works very well (better than my one). I highly recommend testing it yourself. It perfectly solves the problem without much effort.
Edit 2: After around 3 hours of playing, the echo effect bug starts getting hearable again. Not much of a problem though.