His keen ears had caught a sound outside the door.

His keen ears caught the sound of an opening door.

To his keen ear came the low voice of the man at the telephone.

Then to those keen, hidden ears, came a sound from the street outside.

The shadow of a sound had come to those keen ears.

Their keen ears might have picked it up long ago.

To his keen ears had come a weird sound from far off.

Sometimes, one needs very keen ears to understand his experiments.

No sound of breathing within came to her keen ears.

A moment later his keen ears caught the sound of voices.