Doc's voice came back to me, sounding serene.

If that sounds serene, excuse me.

Her tone sounded weirdly serene in her own ears, as if she'd just asked Bothari to pass the butter.

Her voice sounded serene despite the abruptness of her words.

"No dyno in there," Johnny said, still sounding weirdly serene.

"There'll be some way to prove the truth," he soothed, trying to sound serene and confident.

Her clear, quietly resolute voice makes her songs sound serene and assured, even when she's confessing to uncertainty.

He sounded perfectly serene about it.

In comparison, he sounded increasingly serene.

He sounded perfectly serene, perfectly sure of himself.