I just thought I should post this paper that have existed for quite a while.
It has been written by a reputed Norwegian entrepeneur on the subject matter.
Could be read in context with Pauls sequencial troubleshooting on hum and buzz.
https://translate.google.no/translate?hl=&sl=no&tl=en&u=http%3A%2F%2Fsenorc.no%2F%3Fp%3D226