We make it impossible to use, when in fact that voice might greatly strengthen our writing.

He stared again; then his voice strengthened, light seeming to spread from him.

He forced the words out, his voice strengthening the further he went.

"We cannot linger here," he said, his voice strengthening a bit.

Then she seemed to recover, and her voice strengthened again.

Over time, its voice strengthened to the point that it was loud and understandable.

Then, as she came to the end, her voice strengthened.

Panicked, she called out to her friend, and the voice in the darkness strengthened.

Once more he raised himself a little on one elbow, and his voice strengthened.

His voice strengthened with every word, and he gave no indication of having spent the night drinking.