Sparky,

I passed the Question along to a Product Safety Engineering Newsgroup I belong to.

I'll post any relavant responses.

So far:
Quote

>>sounds like a bad rental car experience<< [Linked Image]
(I just got that one!)

>>It's likely a term used to describe the mechanical vibrations that you hear in a magnetic circuit breaker as the current it is carrying increases past its trip current. I've heard this noise, but not the term "Hertz vibration". However the name makes sense - the vibration would be at line frequency.<<

>>Must be something like "line buzz".
Happened at a place where we used a lot
of transfomers. If the transformer wasn't enamalled correctly, there'd be a loose winding that would buzz with the line frequncy.<<

>>The problem with overheard remarks is that you don't know if what is reported is a complete phrase or not. In this case, for example, there would be no mystery if the word 'sixty' occurred before the reported phrase.<<

Bill