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audio signal processing Audio signal processing is a subfield of signal processing that is concerned with the electronic manipulation of audio signals. Audio signals are electronic representations of sound waves— longitudinal waves which travel through air, consist ...
and
acoustics Acoustics is a branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acousticia ...
, an echo is a
reflection Reflection or reflexion may refer to: Science and technology * Reflection (physics), a common wave phenomenon ** Specular reflection, reflection from a smooth surface *** Mirror image, a reflection in a mirror or in water ** Signal reflection, in ...
of sound that arrives at the listener with a delay after the direct sound. The delay is directly proportional to the distance of the reflecting surface from the source and the listener. Typical examples are the echo produced by the bottom of a well, by a building, or by the walls of an enclosed room and an empty room. A true echo is a single reflection of the sound source. The word ''echo'' derives from the
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
ἠχώ (''ēchō''), itself from ἦχος (''ēchos''), "sound".
Echo In audio signal processing and acoustics, an echo is a reflection of sound that arrives at the listener with a delay after the direct sound. The delay is directly proportional to the distance of the reflecting surface from the source and the lis ...
in the Greek folk story is a mountain nymph whose ability to speak was cursed, leaving her able only to repeat the last words spoken to her. Some animals use echo for location sensing and navigation, such as
cetacea Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel th ...
ns (dolphins and whales) and bats in a process known as echolocation. Echoes are also the basis of
Sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances (ranging), communicate with or detect objects on o ...
technology.


Acoustic phenomenon

Acoustic waves are reflected by walls or other hard surfaces, such as mountains and privacy fences. The reason of reflection may be explained as a discontinuity in the
propagation Propagation can refer to: *Chain propagation in a chemical reaction mechanism *Crack propagation, the growth of a crack during the fracture of materials * Propaganda, non-objective information used to further an agenda * Reproduction, and other for ...
medium Medium may refer to: Science and technology Aviation * Medium bomber, a class of war plane * Tecma Medium, a French hang glider design Communication * Media (communication), tools used to store and deliver information or data * Medium ...
. This can be heard when the reflection returns with sufficient magnitude and
delay Delay (from Latin: dilatio) may refer to: Arts, entertainment, and media * ''Delay 1968'', a 1981 album by German experimental rock band Can * '' The Delay'', a 2012 Uruguayan film People * B. H. DeLay (1891–1923), American aviator and ac ...
to be perceived distinctly. When sound, or the echo itself, is reflected multiple times from multiple surfaces, the echo is characterized as a
reverberation Reverberation (also known as reverb), in acoustics, is a persistence of sound, after a sound is produced. Reverberation is created when a sound or signal is reflected causing numerous reflections to build up and then decay as the sound is abso ...
. The human ear cannot distinguish echo from the original direct sound if the delay is less than 1/10 of a second. The velocity of sound in dry air is approximately 343 m/s at a temperature of 25 °C. Therefore, the reflecting object must be more than from the sound source for echo to be perceived by a person located at the source. When a sound produces an echo in two seconds, the reflecting object is away. In nature, canyon walls or rock cliffs facing water are the most common natural settings for hearing echoes. The strength of echo is frequently measured in dB sound pressure level (SPL) relative to the directly transmitted wave. Echoes may be desirable (as in
sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances (ranging), communicate with or detect objects on o ...
) or undesirable (as in
telephone A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into e ...
systems).


Echo in music

In music performance and recording, electric echo effects have been used since the 1950s. The
Echoplex The Echoplex is a tape delay effect, first made in 1959. Designed by Mike Battle, the Echoplex set a standard for the effect in the 1960s—it is still regarded as "the standard by which everything else is measured." It was used by some of the ...
is a tape
delay Delay (from Latin: dilatio) may refer to: Arts, entertainment, and media * ''Delay 1968'', a 1981 album by German experimental rock band Can * '' The Delay'', a 2012 Uruguayan film People * B. H. DeLay (1891–1923), American aviator and ac ...
effect Effect may refer to: * A result or change of something ** List of effects ** Cause and effect, an idiom describing causality Pharmacy and pharmacology * Drug effect, a change resulting from the administration of a drug ** Therapeutic effect, a ...
, first made in 1959 that recreates the sound of an acoustic echo. Designed by Mike Battle, the Echoplex set a standard for the effect in the 1960s and was used by most of the notable guitar players of the era; original Echoplexes are highly sought after. While Echoplexes were used heavily by guitar players (and the occasional bass player, such as
Chuck Rainey Charles Walter Rainey III (born June 17, 1940) is an American bass guitarist who has performed and recorded with many well-known acts, including Aretha Franklin, Steely Dan, and Quincy Jones. Rainey is credited for playing bass on more than 1,00 ...
, or trumpeter, such as
Don Ellis Donald Johnson Ellis (July 25, 1934 – December 17, 1978) was an American jazz trumpeter, drummer, composer, and bandleader. He is best known for his extensive musical experimentation, particularly in the area of time signatures. Later in his li ...
), many
recording studio A recording studio is a specialized facility for sound recording, mixing, and audio production of instrumental or vocal musical performances, spoken words, and other sounds. They range in size from a small in-home project studio large enou ...
s also used the Echoplex. Beginning in the 1970s, Market built the
solid-state Solid state, or solid matter, is one of the four fundamental states of matter. Solid state may also refer to: Electronics * Solid-state electronics, circuits built of solid materials * Solid state ionics, study of ionic conductors and their ...
Echoplex for Maestro. In the 2000s, most echo
effects unit An effects unit or effects pedal is an electronic device that alters the sound of a musical instrument or other audio source through audio signal processing. Common effects include distortion/overdrive, often used with electric guitar in ...
s use electronic or digital circuitry to recreate the echo effect.


Famous echoes

*
Inchindown oil tanks The Inchindown oil tanks is a disused underground oil depot in Invergordon, Ross-shire, Scotland. The tanks hold the record for the longest reverberation in any man-made structure, surpassing the Hamilton Mausoleum in 2014. History The secre ...
, current record holder for longest echo. *
Hamilton Mausoleum Hamilton Mausoleum is a mausoleum located in Hamilton, South Lanarkshire, Scotland. It was the resting place of the family of the Dukes of Hamilton.Hamilton Hamilton may refer to: People * Hamilton (name), a common British surname and occasional given name, usually of Scottish origin, including a list of persons with the surname ** The Duke of Hamilton, the premier peer of Scotland ** Lord Hamilto ...
, South
Lanarkshire Lanarkshire, also called the County of Lanark ( gd, Siorrachd Lannraig; sco, Lanrikshire), is a historic county, lieutenancy area and registration county in the central Lowlands of Scotland. Lanarkshire is the most populous county in Scotl ...
,
Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to ...
: Its high stone means it takes 15 seconds for the sound of a slammed door to delay. *
Gol Gumbaz Gol Gumbaz (), also written Gol Gumbad, is a 17th-century mausoleum located in Bijapur, a city in Karnataka, India. It houses the remains of Mohammad Adil Shah, seventh sultan of the Adil Shahi dynasty, and some of his relatives. Begun in the ...
of
Bijapur Bijapur, officially known as Vijayapura, is the district headquarters of Bijapur district of the Karnataka state of India. It is also the headquarters for Bijapur Taluk. Bijapur city is well known for its historical monuments of architectural i ...
,
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
: Any whisper, clap or sound gets echoed repeatedly. * The
Golkonda Fort (Telugu: గోల్కొండ, romanized: ''Gōlkōnḍa'') is a historic fortress and ruined city located in Hyderabad, Telangana, India. It was originally called Mankal. The fort was originally built by Kakatiya ruler Pratāparu ...
Fort of
Hyderabad Hyderabad ( ; , ) is the capital and largest city of the Indian state of Telangana and the ''de jure'' capital of Andhra Pradesh. It occupies on the Deccan Plateau along the banks of the Musi River, in the northern part of Southern Indi ...
,
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
* The Echo Wall at the
Temple of Heaven The Temple of Heaven () is a complex of imperial religious buildings situated in the southeastern part of central Beijing. The complex was visited by the Emperors of the Ming and Qing dynasties for annual ceremonies of prayer to Heaven for a ...
,
Beijing } Beijing ( ; ; ), Chinese postal romanization, alternatively romanized as Peking ( ), is the Capital city, capital of the China, People's Republic of China. It is the center of power and development of the country. Beijing is the world's Li ...
,
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
* The Whispering Gallery of
St Paul's Cathedral St Paul's Cathedral is an Anglicanism, Anglican cathedral in London and is the seat of the Bishop of London. The cathedral serves as the mother church of the Diocese of London. It is on Ludgate Hill at the highest point of the City of London ...
,
London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...
, England, UK *
Echo Point ''Echo Point'' is an Australian television soap opera produced by Southern Star Group for Network Ten on 1 June 1995 until 1 December 1995. The series was devised as an attempt by the Ten Network to rival the opposition soap ''Home and Away' ...
, the Three Sisters, Katoomba,
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
* The Temple of Kukulcan
El Castillo, Chichen Itza El templo, known as the Temple of Kukulcán (or also just as Kukulcán), is a Mesoamerican step-pyramid that dominates the center of the Chichen Itza archaeological site in the Mexican state of Yucatán. The temple building is more formally des ...
,
Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...
* The
Baptistry of Pisa The Pisa Baptistery of St. John ( it, Battistero di San Giovanni) is a Roman Catholic ecclesiastical building in Pisa, Italy. Construction started in 1152 to replace an older baptistery, and when it was completed in 1363, it became the second b ...
,
Pisa Pisa ( , or ) is a city and ''comune'' in Tuscany, central Italy, straddling the Arno just before it empties into the Ligurian Sea. It is the capital city of the Province of Pisa. Although Pisa is known worldwide for its leaning tower, the ci ...
,
Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...
* The echo near
Milan Milan ( , , Lombard: ; it, Milano ) is a city in northern Italy, capital of Lombardy, and the second-most populous city proper in Italy after Rome. The city proper has a population of about 1.4 million, while its metropolitan city ...
visited by
Mark Twain Samuel Langhorne Clemens (November 30, 1835 – April 21, 1910), known by his pen name Mark Twain, was an American writer, humorist, entrepreneur, publisher, and lecturer. He was praised as the "greatest humorist the United States has pr ...
in '' The Innocents Abroad'' * The echo in
Chinon Chinon () is a commune in the Indre-et-Loire department, Centre-Val de Loire, France. The traditional province around Chinon, Touraine, became a favorite resort of French kings and their nobles beginning in the late 15th and early 16th centurie ...
,
France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
which is used in a traditional local rhyme * The gazebo of Napier Museum in Trivandrum, Kerala, India


See also

*
Light echo 309x309px, Reflected light following path B arrives shortly after the direct flash following path A but before light following path C. B and C have the same apparent distance from the star as seen from Earth.">Earth.html" ;"title="apparent distan ...


References


External links


More information on Chinon echo.

Listen to Duck echoes and an animated demonstration of how an echo is formed.
{{Acoustics Acoustics Audio effects