My African Bullfrog only makes his cow noise every once in a while and I can hear it if my apartment is completely quiet (no TV, AC, cooking, etc.) and I'm in the area his house is in. I've seen those videos of African Bullfrogs (and other types) screaming but I've never seen one do that in real life and I don't imagine it would happen unless the frog was terrified and/or becoming very defensive due to provocation. Your neighbors definitely won't hear it.