somebody's voice breaks
somebody's voice cracks
somebody's voice shakes
somebody's voice trembles

The big man started to speak, but his voice cracked.

He heard his own voice, on the words, crack a little.

His voice tried to be hard and cracked on the word.

His voice cracked a little on the last two words.

His voice cracked a little bit on that last word.

Which would have been fine if my voice had not cracked as I said it.

There could be only one answer, but his voice still cracked.

Then he forced himself to go on, his voice cracking.

His voice cracked and he couldn't hold a key, but that didn't seem to matter.

I'm all alone here with my little girl,' Had her voice cracked?