He glanced to the tower as the triangle sounded once.

Her constant criticism surely once sounded like, and was intended as encouragement.

It once sounded, depressingly perhaps, like a trait only people have.

The drumbeat sounded once, then stopped again, a rare staccato.

As though to underscore his words a great bell sounded once, then once again.

It sounded like a good deal once, and may again someday (though not too soon, I hope).

When required the foghorn sounds once every 60 seconds.

The owl and the fox cry where laughter once sounded.

In the harbor, a deep horn sounded once, then again.

On the tape the knock sounded once, twice, three times.