Incompatible rear derailleur?

[growingvegetables]

... it occurs twice per revolution ...

... per revolution of which, pedal or wheel?

Things that have clicked annoyingly for me, and been hardest to "place" - pedal bearing about to give up the ghost; the magnet for my computer out of line (infuriating when I finally found it - it sounded like it was coming from somewhere completely different when I was riding).

 

[franz10mp]

When I pedal it seems revolution of pedal, but when I stop pedalling the noise is still there. So it might be revolution of wheel because the rear wheel is the only thing in movement.

And maybe yes, it does not come from the crank area, but it seems so.