The squeakier call could also be a release call. Or just your confirmed adult not putting his heart into the calling process and delivering a weak effort.

My male Hyla versicolor can trill with the best of them, but he also puts out some odd noises that have had me running to check on who it's coming from so I've come to expect more than just the 'stock' calls to come from an adult male of other species. I think it's probably best to catch them in the act.