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

A woman asked what he wanted in a voice trembling with fear.

Just listen to you, your voice is even trembling with fear.

His voice was trembling at the far edge of control.

When he finally called after a week, his voice trembled.

But now he was pretty sure his voice wouldn't tremble.

"I don't know why you want to go out with me," she said, her voice small and trembling.

"I just want to know one thing," she said, her voice trembling only a little.

Then she continued in a lower tone, her voice trembling at times.

His voice trembled, and he did not want West to see him like this.

But if this were so her voice trembled not at all.