Whispering gallery
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A whispering gallery is usually a circular, hemispherical, elliptical or ellipsoidal enclosure, often beneath a dome or a vault, in which whispers can be heard clearly in other parts of the gallery. Such galleries can also be set up using two parabolic dishes. Sometimes the phenomenon is detected in caves.
Theory
A whispering gallery is most simply constructed in the form of a circular wall, and allows whispered communication from any part of the internal side of the circumference to any other part. The sound is carried by waves, known as whispering-gallery waves, that travel around the circumference clinging to the walls, an effect that was discovered in the whispering gallery of St Paul's Cathedral in London.<ref>Lord Rayleigh, The problem of the whispering gallery, Philos. Mag. 20, 1001,1910.</ref> The extent to which the sound travels at St Paul's can also be judged by clapping in the gallery, which produces four echoes.<ref>O. Wright, Gallery of Whispers, Physics World 25, No. 2, Feb. 2012, p. 31. </ref> Other historical examples<ref name=raman>Template:Cite journal</ref><ref name=sab>W. C. Sabine, Collected Papers on Acoustics (Harvard University Press, Cambridge MA) 1922, p. 255.</ref><ref name=Peiping>Peiping (American National Red Cross, American Red Cross Embassy Club) 1946, p. 17.</ref> are the Gol Gumbaz mausoleum in Bijapur, India and the Echo Wall of the Temple of Heaven in Beijing. A hemispherical enclosure will also guide whispering gallery waves. The waves carry the words so that others will be able to hear them from the opposite side of the gallery.
The gallery may also be in the form of an ellipse or ellipsoid,<ref name=sab /> with an accessible point at each focus. In this case, when a visitor stands at one focus and whispers, the line of sound emanating from this focus reflects directly to the focus at the other end of the gallery, where the whispers may be heard. In a similar way, two large concave parabolic dishes, serving as acoustic mirrors, may be erected facing each other in a room or outdoors to serve as a whispering gallery, a common feature of science museums. Egg-shaped galleries, such as the Golghar Granary at Bankipore,<ref name=raman/> and irregularly shaped smooth-walled galleries in the form of caves, such as the Ear of Dionysius in Syracuse,<ref name=sab /> also exist.
Examples
India
- The Gol Gumbaz in Bijapur, India.<ref name=raman/>
- The Golghar Granary in Bankipore, India.<ref name=raman/>
- The Victoria Memorial in Kolkata.<ref name=raman/>
United Kingdom
- St Paul's Cathedral in London is the place where whispering-gallery waves were first discovered by Lord Rayleigh Template:Circa.<ref>Lord Rayleigh, Theory of Sound, vol. II, 1st edition, (London, MacMillan), 1878.</ref>
- Gloucester Cathedral has a whispering gallery.<ref>Template:Cite web</ref>
- The Berkeley Wetherspoons Bristol has a whispering gallery.<ref>Template:Cite web</ref>
United States
- Grand Central Terminal in New York City: a landing amid the Oyster Bar ramps, in front of the Oyster Bar restaurant <ref>Template:Cite web</ref>
- Statuary Hall in the United States Capitol.<ref name=raman/>
- Salt Lake Tabernacle in Salt Lake City, Utah<ref name=raman/>
- Centennial fountain in front of Green Library at Stanford University in California<ref>Template:Cite web</ref>
- Gates Circle, Buffalo, New York<ref>Template:Cite web</ref>
- The Whispering Arch in St. Louis Union Station<ref name=waymarking>Waymarking.com, St. Louis Union Station Whispering Arch</ref>
- Charles Stover Bench, Central Park, New York, New York <ref>Template:Cite web</ref>
- Waldo Hutchins Bench, Central Park, New York, New York<ref>Template:Cite web</ref>
- Whispering Gallery, Museum of Science and Industry (Chicago)<ref>Whispering Gallery at MSI Chicago</ref>
Other parts of the world
- The Echo Wall in the Temple of Heaven in Beijing.<ref name=Peiping />
- Basilica of St. John Lateran, Rome.<ref name=sab />
- The Salle des Caryatides in the Louvre, Paris, France.<ref name=sab />
- Ear of Dionysius cave in Syracuse, Sicily.<ref name=sab />
- Palazzo del Podestà, Bologna, Italy.<ref name=sab />
- Banco dos Namorados (Lovers' bench) in Santiago de Compostela, Spain.<ref>Template:Cite web</ref>
In science
The term whispering gallery has been borrowed in the physical sciences to describe other forms of whispering-gallery waves such as light or matter waves.<ref>Template:Cite journal</ref>
See also
References
External links
- Ear of Dionysius: visiting information, videos and sounds of this cave.
- Grand Central Station: visiting information, videos and sounds of the whispering gallery.
- St Paul's Cathedral: visiting information, videos and sounds of the whispering gallery.