1.   Sanders gave a low whistle when he saw the contents of the box.

2.   Jackson gave a low whistle.

3.   We could hear the low whistle of the wind through the trees.

4.   Lloyd let out a low whistle.

5.   When she finished David let out a low whistle.

6.   As we watched, its mother flew down, encouraging it with a few low whistles.

7.   One player let out a low whistle.

8.   Radio conversations were kept to a minimum and most communications were whispers, low whistles or hand signals.

9.   Then came a low whistle, a signal from a smuggler acting as advance man.