The successful candidates were beside themselves with joy.
TTS sounds unnatural for two reasons.
喜びのあまり is in one phrase, and a pause is needed between あまり and 我. But TTS pronounces あまり我 as one phrase.
TTS puts the accent on ま, the second syllable of あまり. But it means “not so much”. You need to put the accent of あ instead so that あまり in this context means “due to so much of excitement”. あまる in this sentence is derived from 余る, which means “to exceed a certain threshold”.