The spurt of sound had dropped a full octave.

I'd lowered the volume on my voice, but the pitch was still a full octave higher than normal.

She was fair to look upon and her voice was sweet and pure and in range two full octaves.

"You bitch!" she shrieked, her voice a full octave above its normal range.

"Bilairy's hairy bag!" he croaked, his voice a full octave higher than normal.