vostro bad sound quality

Nice machine. It has been plagued by speaker distortion almost since new. As a result, Dell technicians have replaced both speakers. This repairs the issue temporarily until sound on a YouTube vid for example is terrible to listen to. I have read   Audio Distortion or Speaker Static Noise on Latitude, XPS, Inspiron, Precision, and Vostro Laptops | Dell Australia 
as a possible issue. This has worked to some degree, but gradually reverts back to distortion with people speaking. The issue is now affecting music.
Is anyone aware of this issue, possibly with the software, and not the speakers?