Walls have cracks and partitions ears.
Chinese proverb

Several cultures share in this proverbial adage warning others that they may be overheard without their knowing it.

In South Africa they say,
"Walls have ears, and little pots too."

In Japan,
"Walls have ears, bottles have mouths," and sometimes it’s even a little more disturbing,
"Walls have ears, paper sliding doors have eyes."

The Chinese, Dutch, French, German, and Portuguese all agree that,
“Walls have ears.”

and the Persians said, "Walls have mice and mice have ears."

The metaphor is a precaution or advice to speak discreetly; you could be overheard anywhere without knowing it. The first English attribution comes from a manuscript dating around the 1300’s called King Edward and the Shepherd where the author warns,
Wode has erys, felde has sigt.

Around the same era Geoffrey Chaucer (c. 1340–1400) wrote in The Knightes Tale of the Canterbury Tales
”That field hath eyen, and the wood hath ears.” By 1869 English bibliographer William Carew Hazlitt, had shortened the adage to simply, “Walls have ears.”

"How can you be deaf with ears like those?"
--Dr. McCoy, Star Trek III: The Search For Spock

Today there are vast arrays of state-of-the-art technologies for listening in on other people’s conversations, but there was an era when “the walls” actually “had ears.” In ancient Syracuse, prisoners carved a large ear-shaped underground cave out of solid rock. It’s a curious and impressive 200 feet deep limestone cavern with an entrance in the form of a Vulcan like ear. The story is legendary, but the acoustics are so spectacular choirs practice there today. From the small opening on the top the tyrant Dionysus would eavesdrop on the conversations of his captives. The shape of the Ear focuses sound waves so that whispers on one end can be heard clearly on the other end. Later on the famous painter Caravaggio (1573-1610) gave it its legendary name the Ear of Dionysus and has come to generically refer to any such structure because its shape resembles the twisting curves of a human ear.

In one ear...

Hundreds of year ago in Agrigento, Sicily a cathedral was built with a curved roof and an elliptical shape and that echoed words spoken at one focal point of the ellipse to the other focal point across the area, says John Tyndall in The Science of Sound. Shortly after the cathedral's construction, the confessional was unwittingly located at one of these acoustical "hotspots," a fact revealed quite by accident.

...and out the other.
John Heywood (1546)

She was a major force in French politics during the three decades of Roman Catholic-Huguenot Wars and the instigator of the Saint Bartholomew's Day Massacre. In addition to her political role, Catherine de Medici was also a patron of the arts. Her interest in architecture was demonstrated in the building of a new wing of the Louvre Museum. While priceless art hung on one side of the walls “tubes of communication” called the auriculaires were constructed on the inside of the walls based on “the same principle as those of the confessionals.” It was by this apparatus that the suspicious queen kept up to date with conspiracies and state secrets.

Seal up your lips, and give no words but mum: The business asketh silent secrecy.
(Henry VI, Part II)

Mum’s the word for the only sound Shakespeare says you can make with your lips sealed. There is also the alternative of doing things sub rosa, Latin for “under the rose.” Roses were sculpted or painted on the ceiling of banquet halls to remind revelers to watch their words. The royal family eventually installed ear shaped whispering galleries in Hastings Castle. Whispering galleries explains James A. Sellers, “are rooms whose ceilings are elliptical, a sound made at one focus of the ellipse will be reflected to the other focus (across the room), allowing people standing at the two foci to hear one another very clearly. This has been called the "whispering gallery" effect and has been used by many in the design of special rooms. In particular, St. Paul's Cathedral and one of the rooms at the United States Capitol were built with this in mind.”

Are your ears burning yet?

After the War of 1812 along with several features created at Fort Adams, Rhode Island were an underground network of tunnels called listening galleries. As an existing example of the highest advances in masonry fortification wouldn’t you know it, the designer of Fort Adams was a French engineer officer named Simon Bernard (1779 - 1839). Bernard, a graduate of the École Polytechnique, had served as a lieutenant general of engineers under Napoleon Bonaparte.

Sources:

AllWords.com:
adams.allwords.com/word-wall.html
Accessed Jan 30 2004.

A word with you :
http://www.wordwithyou.com/columns/1_10_99.gif
Accessed Jan 30 2004.

E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.

Bartleby.com:
http://www.bartleby.com/81/17244.html
Accessed Jan 30 2004.

GIGA Quote Topic Page for Proverbs:
www.giga-usa.com/gigaweb1/quotes2/ qutopproverbsx313.htm
Accessed Jan 30 2004.

Strange but True: Cincinnati.Com:
www.cincinnati.com/freetime/ strange/061899_strange.html
Accessed Jan 30 2004.

Whispering Galleries:
www.krellinst.org/UCES/archive/ resources/conics/node70.html
Accessed Jan 30 2004.