answer:Assuming it was the bat making these sounds, you might have been hearing social calls. Apparently these occur with every 10 or 20 chirps in some species. I’m having trouble finding examples online that can be listened to (aside from the one in the Wikipedia article). I found one journal article which has some good animations showing bat interactions with the soundtrack of social calls. I might be able to get that to you via email, if you PM me – though they don’t sound exactly like what you described. As to which species… there are 28 species of bat in Arizona, so I’m not sure that can be pinned down easily without seeing it. But if you’re keen, see if there are any nearby university profs who study bats, and send a query by email. They would probably know.