My Toshiba laptop is making a loud whirring noise. What causes this!

For everyone experiencing issues with Toshiba L500-20z making a horrible whistle when audio plays, try to delete and reinstall audio drivers. For some reason the updated drivers turn the speakers into a medieval torture.

I was having that problem also. I have a Toshiba Satelite that’s a few years old. After taking the back off (there are screws hidden beneath the pads closest to the hinge) I figured out that although the fan was clean it would sometimes hit against the fan housing when it spun at certain speeds. Instead of a gentle whir it was really loud. I fixed it by repositioning a silver pad that was stuck to the case a couple of inches from the fan so that was centered over the fan. The slight pressure between the fan and the case seems to keep the fan from hitting the housing.