[yomly]

Plenty of devices have loud fans irrespective of their current CPU load. Being facetious, there also exist fanless PCs submerged in oil which do not make sounds based on CPU load.

Checking your CPU usage via `top` is a relatively "power-user" esque function so your experience is unlikely to be reflective of the general population.

[greglindahl]

Firefox has a popup when it notices any tab using a lot of cpu -- no need to run 'top'.