In audio signal processing and acoustics, an echo (plural echoes) is a reflection of sound, arriving at the listener some time after the direct sound. Typical examples are the echo produced by the bottom of a well, by a building, or in a room, by the walls. A true echo is a single reflection of the sound source. The time delay is the extra distance divided by the speed of sound. This article or section does not cite its references or sources. ... Acoustics is a branch of physics and is the study of sound (mechanical waves in gases, liquids, and solids). ... Spheres reflecting the floor and each other. ... The speed of sound is a term used to describe the speed of sound waves passing through an elastic medium. ...

If so many reflections arrive at a listener that he is unable to distinguish between them, the proper term is reverberation. This article is about audio effect. ...

An echo can be explained as a wave that has been reflected by a discontinuity in the propagation medium, and returns with sufficient magnitude and delay to be perceived. Wave propagation refers to the ways waves travel through a medium (waveguide). ... A transmission medium is any material substance, such as fiber-optic cable, twisted-wire pair, coaxial cable, dielectric-slab waveguide, water, or air, that can be used for the propagation of signals, usually in the form of modulated radio, light, or acoustic waves, from one point to another. ... Delay is: In sound effects, any of a class of effect that adds one or more delayed versions of the original signal, to create effects such as echo or flanger. ...

When dealing with audible frequencies, the human ear cannot distinguish an echo from the original sound if the delay is less than 1/10 of a second. Thus, since the velocity of sound is approximately 343 m/s at a normal room temperature of about 20°C, a reflecting wall must be more than 16.2 m from the sound source at this temperature for an echo to be heard by a person at the source. Delay is: In sound effects, any of a class of effect that adds one or more delayed versions of the original signal, to create effects such as echo or flanger. ...

The strength of an echo is frequently measured in dB sound pressure level SPL relative to the directly transmitted wave. Image File history File links Echo_samples. ... Software development stages In computer programming, development stage terminology expresses how the development of a piece of software has progressed and how much further development it may require. ... The decibel (dB) is a dimensionless unit of ratio which is used to express the relationship between a variable quantity and a known reference quantity. ...

Echoes may be desirable (as in sonar) or undesirable (as in telephone systems). The F70 type frigates (here, La Motte-Picquet) are fitted with VDS (Variable Depth Sonar) type DUBV43 or DUBV43C towed sonars SONAR (SOund Navigation And Ranging) â€” or sonar â€” is a technique that uses sound propagation under water (primarily) to navigate, communicate or to detect other vessels. ... The telephone or phone is a telecommunications device which is used to transmit and receive sound (most commonly voice and speech) across distance. ...

In computing, an echo is the printing or display of characters (a) as they are entered from an input device, (b) as instructions are executed, or (c) as retransmitted characters received from a remote terminal. Originally, the word computing was synonymous with counting and calculating, and a science and technology that deals with the original sense of computing mathematical calculations. ... The term input has a variety of uses in different fields. ... A computer terminal is an electronic or electromechanical hardware device that is used for entering data into, and displaying data from, a computer or a computing system. ...

In computer graphics, an echo is the immediate notification of the current values provided by an input device to the operator at the display console. Computer graphics is a sub-field of computer science and is concerned with digitally synthesizing and manipulating visual content. ...

Some information from Federal Standard 1037C and from MIL-STD-188. Federal Standard 1037C entitled Telecommunications: Glossary of Telecommunication Terms is a U.S. Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended. ... MIL-STD-188 is a series of U.S. military standards relating to telecommunications. ...

Mythology

The name "echo" comes from the Greek nymph Ηχώ from Greek mythology. According to Greek mythology Echo was an Oread who had the job of talking incessantly to Hera, the Queen of the Gods, so that her husband, Zeus, wouldn't get caught in his numerous affairs. Hera caught on to Echo's trick and cursed her to only be able to say what others had just said — hence the word "echo". Yet according to Roman mythology it was Pan, who when Echo denied his love, tore her to shreds and scattered her about the Earth leaving bits of her everywhere for us to find, or rather for us to hear, forever. In Greek mythology, a nymph is any member of a large class of female nature entities, either bound to a particular location or landform or joining the retinue of a god or goddess. ... The bust of Zeus found at Otricoli (Sala Rotonda, Museo Pio-Clementino, Vatican) Greek mythology is the body of stories belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world and their own cult and ritual practices. ... Echo and Narcissus, by John William Waterhouse. ... In Greek mythology, Oreads (ὄρος, mountain) were a type of nymph that lived in mountains, valleys, ravines, and differ from each other according to their dwelling. ... In the Olympian pantheon of classical Greek Mythology, Hera (IPA pronunciation: ; Greek or ) was the wife and older sister of Zeus. ... The Statue of Zeus at Olympia Phidias created the 12-m (40-ft) tall statue of Zeus at Olympia about 435 BC. The statue was perhaps the most famous sculpture in Ancient Greece, imagined here in a 16th century engraving Zeus (in Greek: nominative: Zeús, genitive: Diós), is... Pan (Greek , genitive ) is the Greek god of nature who watches over shepherds and their flocks: paein means to pasture. ... Echo and Narcissus, by John William Waterhouse. ...

Duck's quack

"A duck's quack doesn't echo," is a much quoted scientific myth. The truth is that a duck's quack in fact, does echo, however it may be difficult to hear. This myth was first debunked by the Acoustics Research Centre at the University of Salford in 2003 as part of the British Association's Festival of Science. It also featured in one of the earlier episodes of the popular Discovery Channel television show "MythBusters." The University of Salford is a large University situated in the city of Salford in Greater Manchester, England. ... The British Association or the British Association for the Advancement of Science or the BA is a learned society with the object of promoting science, directing general attention to scientific matters, and facilitating intercourse between scientific workers. ... MythBusters is an American pop science television program on the Discovery Channel starring special effects experts Adam Savage and Jamie Hyneman, who use their skills and expertise to test the validity of various rumors and urban legends in popular culture. ...

Famous echoes

• The Golkonda (a.k.a Golconda) Fort of Hyderabad, India
• The Whispering Gallery of St Paul's Cathedral, London, England
• Echo Point, the Three Sisters, Katoomba, Australia
• The Temple of Kukulcan ("El Castillo"), Chichen Itza, Mexico [1]

Golconda is a ruined city and fortress 11 km west of the city of Hyderabad, Andhra Pradesh state, India. ... Hyderabad may refer to: Hyderabad, the independent state Hyderabad State, the pre-1956 state India Hyderabad, Andhra Pradesh, the capital city of the Indian state of Andhra Pradesh Hyderabad district (India) Begumpet Airport, also known as Hyderabad Airport Hyderabad Central, a huge shopping mall in Hyderabad Hyderabad, Uttar Pradesh, a... This article is about the cathedral church of the diocese of London. ... This article is about the capital of England and the United Kingdom. ... Motto: (French for God and my right) Anthem: God Save the King/Queen Capital London (de facto) Largest city London Official language(s) English (de facto) Unification    - by Athelstan AD 927  Area    - Total 130,395 km² (1st in UK)   50,346 sq mi  Population    - 2006 est. ... The Three Sisters The Three Sisters towering above the Jamison Valley. ... Katoomba is the chief town of the City of the Blue Mountains in New South Wales, Australia and is its administrative headquarters. ... Temple of the Warriors Chichen Itza is the largest of the Pre-Columbian archaeological sites in Yucat n, Mexico. ...

External links

[*http://www.acoustics.salford.ac.uk/acoustics_world/duck/duck.htm Listen to duck echoes and check out the myth]