Is their an average frequency range of a feedback loop.
One created by a speaker and a mic to be slightly more specific.
Do you mean in livesound situations? If so, it depends on soo many factors that it is impossible to give a average frequency range. But something i noticed when working with a band that only use in-ears is that feedback through FoH started (if at all) around the lower midrange. I think this is common due to the way lower frequencies radiate. With the band i toured with, a common frequencyarea that feedbacked was around 160-200, probably due to the many acoustic guitars used that resonate around these frequencies.
Remember that what i say only applies to the situation i am in with this band and certain circumstances. If you use wedges and those types of monitors other areas might feedback more often due to the length between the wedges and the mics etc etc. Like i said in the beginning, it depends on so many factors... Still, hope this helps :).
If you want to find the frequency as it happens, try this nice little freebie - Sonoma Feedback Detector
No affiliation, I've just found it useful myself.
Very rough guesses…