1 Even the walls have ears.

2 Hedges have eyes, and walls have ears. 

3 Pitchers/Walls have ears.

4 Walls have ears.

5 Be careful what you say; even the walls have ears!

6 Not so loud. Walls have ears.

7 Hedge have eyes and walls have ears.

8 Hedges have eyes, walls have ears.

9 Walls have ears, you know.

10 The walls have ears, so be careful about what you say.

11 Shall I come to your hotel? Better if we meet in the Park. Walls have ears.