Dog barking/whining?

My dog is an 8 month old german shepherd cross, she constantly barks and whines and howls when we are not home, I have tried an anti-bark collar, no dont worry it is the humaine one that just sprays citranella at her when she barks, I have tried placing a radio near her, a ticking clock ( she is in a crate ) I have tried puting a blanket over her crate... nothing works.. I always have a my landlord tell me she barked liked crazy... any ideas?