echo

1. 1. Repetition of a sound by reflection of sound waves from a surface.
   2. The sound produced in this manner.
2. A repetition or an imitation: a fashion that is an echo of an earlier style.
3. A remnant or vestige: found echoes of past civilizations while examining artifacts in the Middle East.
4. One who imitates another, as in opinions, speech, or dress.
5. A sympathetic response: Their demand for justice found an echo in communities across the nation.
6. A consequence or repercussion: Her resignation had echoes throughout the department.
7. Repetition of certain sounds or syllables in poetry, as in echo verse.
8. Music. Soft repetition of a note or phrase.
9. Electronics. A reflected wave received by a radio or radar.

1. To repeat (a sound) by the reflection of sound waves from a surface.
2. To repeat or imitate: followers echoing the cries of their leader; events that echoed a previous incident in history.

1. To be repeated by or as if by an echo: The shout echoed off the wall. The speaker's words echoed in her mind.
2. To resound with or as if with an echo; reverberate: rooms echoing with laughter.

[Middle English, from Old French, from Latin ēchō, from Greek ēkhō.]

SYNONYMS   echo, reecho, reflect, resound, reverberate. These verbs mean to send back the sound of: a cry echoed by the canyon; a cathedral roof reechoing joyous hymns; caves that reflect the noise of footsteps; cliffs resounding the thunder of the ocean; blasting reverberated by quarry walls.

A sound wave which has been reflected or otherwise returned with sufficient magnitude and time delay to be perceived in some manner as a sound wave distinct from that directly transmitted. Multiple echo describes a succession of separately indistinguishable echos arising from a single source. When the reflected waves occur in rapid succession, the phenomenon is often termed a flutter echo. Echoes and flutter echoes are generally detrimental to the quality of the acoustics of rooms. They may be minimized through the proper selection of room dimensions, room shape, and distribution of sound-absorbing materials.

Echoes have been put to a variety of uses in measurement problems. For example, the distance between two points can be measured by timing the duration required for a direct sound originating at one location to strike an object at the other point and to return an echo to the location of the initial source. Ultrasonic echo techniques have achieved considerable success in nondestructive testing of materials. See also Echo sounder; Echocardiography; Reflection of sound; Sonar; Sound; Ultrasonics.

(1) A repetition of a signal in a communications line. The difference in electrical characteristics at opposite ends can cause the echo.

(2) In communications, to transmit received data back to the sending station allowing the user to inspect visually what was received. A local echo displays what you type on your screen.

(3) A DOS and OS/2 screen command that displays messages and turns off/on screen responses. See DOS batch file.

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noun

1. Repetition of sound via reflection from a surface: repercussion, reverberation. See sounds/pleasant sounds/unpleasant sounds/neutral sounds or silence.
2. Imitative reproduction, as of the style of another: imitation, reflection, reflex, repetition. See same/different/compare.
3. One who mindlessly imitates another: imitator, mimic, parrot. See same/different/compare.

verb

1. To send back the sound of: rebound, reecho, reflect, repeat, resound, reverberate. See sounds/pleasant sounds/unpleasant sounds/neutral sounds or silence.
2. To copy (another) slavishly: image, imitate, mimic, mirror, parrot, reflect, repeat. See same/different/compare.

Echo effects are caused by the reflection of sound waves from distant surfaces. The effect has been imitated in music, for example in 16th-century madrigals; it became popular in dramatic works in the 17th century and sometimes gave opportunities for punning effects (for example as in Cavalieri's Rappresentazione di Anima, et di Corpo, 1600, where the Soul asks ‘Chi dalla morte al cor con dispiacere?’ and is answered ‘Piacere’). There are also examples, suggesting a ‘deep-vaulted cell’, in Purcell's Dido and Aeneas. Mozart uses echoes of diminishing length in his Serenade for four orchestras k 286/269 a; Wagner uses a sinister mis-echo in The Flying Dutchman to suggest a ghost ship.

An Echo Organ is an encased subsidiary chest within the main organ, usually with its own keyboard.

Sound waves which have been reflected to a listener with sufficient magnitude and time delay so as to be perceived separately from those communicated directly to the listener.

A reflected sound; the basis for echocardiography and ultrasonography.

The repetition of particular sounds, syllables, words or lines in poetry.

(Commtalk) E.

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 by the walls of an enclosed room. A true echo is a single reflection of the sound source. The time delay is the extra distance divided by the speed of sound.

Contents 1 Acoustic phenomenon 2 In computing 3 In music 4 Mythology 5 Duck's quack 6 Famous echoes 7 External links

Acoustic phenomenon

If so many reflections arrive at a listener that they are unable to distinguish between them, the proper term is reverberation. 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. Echoes are reflected off walls or hard surfaces like mountains and privacy fences.

This illustration depicts the principle of sediment echo sounding, which uses a narrow beam of high energy and low frequency

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, the reflecting object 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.

Sound travels approximately 343 meters/s (1100 ft/s). If a sound produces an echo in 2 seconds, the object producing the echo would be half that distance away (the sound takes half the time to get to the object and half the time to return). The distance for an object with a 2-second echo return would be 1 sec X 343 meters/s or 343 meters (1100 ft). In most situations with human hearing, echoes are about one-half second or about half this distance, since sounds grow fainter with distance. In nature, canyon walls or rock cliffs facing water are the most common natural settings for hearing echoes.The strength of an echo is frequently measured in dB sound pressure level SPL relative to the directly transmitted wave. Echoes may be desirable (as in sonar) or undesirable (as in telephone systems).

In computing

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. 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.

Some information from Federal Standard 1037C and from MIL-STD-188.

In music

In music performance and recording, electric echo effects have been used since the 1950s. The Echoplex is a tape delay effect, 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, or trumpeter, such as Don Ellis), many recording studios also used the Echoplex.Beginning in the 1970s, Market built the solid-state Echoplex for Maestro. In the 2000s, most echo effects units use electronic or digital circuitry to recreate the echo effect.

Mythology

The name "echo" comes from the Greek nymph Ηχώ from Greek mythology. According to Greek mythology Echo was a Nymph who had the job of talking incessantly to Hera, the Queen of the Gods, so that her husband, Zeus, would not 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".

Duck's quack

"A duck's quack doesn't echo" is a much-quoted scientific myth. The truth is that a duck's quack does, in fact, 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 was also featured in one of the earlier episodes of the popular Discovery Channel television show MythBusters. The actual reason for the myth is that the wave of a duck's quack is almost identical to an echo. It echoes, but it is not very obvious.

Famous echoes

	Echo samples Clean signal, followed by different versions of echo.
Problems listening to this file? See media help.

• Gol Gumbaz of Bijapur, India: Any whisper, clap or sound gets echoed repeatedly.
• The Golkonda 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]
• The Baptistry of Pisa, Pisa,Italy
• The echo near Milan visited by Mark Twain in The Innocents Abroad

External links

• Listen to Duck echoes and a animated demonstration of how a echo is formed.

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Dansk (Danish)
n. - ekko, genlyd, efterlignelse
v. tr. - kaste tilbage, gentage
v. intr. - give genlyd, genlyde

idioms:

• echo chamber    ekkorum
• echo sounder    ekkolod

Nederlands (Dutch)
weergalmen, echo, weerklank, na-aper

Français (French)
n. - écho, (fig) écho, rappel
v. tr. - renvoyer, répercuter, (fig) répéter, se faire l'écho
v. intr. - retentir, résonner, se répercuter, faire écho, renvoyer l'écho

idioms:

• echo chamber    (Radio, TV) chambre sonore
• echo sounder    (Naut) sondeur (à ultra sons)

Deutsch (German)
v. - zurückwerfen, widerhallen, nachsprechen
n. - Echo, Anklang

idioms:

• echo chamber    Raum mit geräuschwiedergebenden Wänden
• echo sounder    Echolot

Ελληνική (Greek)
v. - αντηχώ, αντιλαλώ, απηχώ, (μτφ.) μιμούμαι, επαναλαμβάνω
n. - ηχώ, αντήχηση, αντίλαλος, απόηχος, (μτφ.) επίπτωση, συνέπεια, απόηχος

idioms:

• echo chamber    δωμάτιο με ηχητικότητα
• echo sounder    ηχοβολιστικό μηχάνημα

Italiano (Italian)
echeggiare, eco

idioms:

• echo chamber    camera di risonanza
• echo sounder    ecoscandaglio

Português (Portuguese)
v. - ecoar
n. - eco (m)

idioms:

• echo chamber    câmara (f) de ressonância (Fís.)
• echo sounder    ecômetro (m) (Fís.)

Русский (Russian)
вторить, звенеть, эхо

idioms:

• echo chamber    эхокамера
• echo sounder    эхолот

Español (Spanish)
n. - eco, resonancia, repetición, repetición o imitación cercana de las ideas u opiniones de otro, persona que refleja o imita a otra, respuesta idéntica en lo que se refiere a los sentimientos, efecto persistente, (mitología) ninfa que desfallece por el amor hacia el hermoso joven Narciso hasta que solo permanece su voz, jugar una carta alta y luego una baja siguiendo el palo que inició el compañero, tal como una señal para seguir en ese palo, como en el bridge p matar con un triu
v. tr. - hacer eco, retumbar, resonar
v. intr. - hacer eco, retumbar, resonar

idioms:

• echo chamber    cámara de resonancia
• echo sounder    sonda acústica, ecómetro

Svenska (Swedish)
v. - eka, återkasta
n. - eko

中文（简体）(Chinese (Simplified))
回声, 回波, 回音, 摹仿, 反射, 重复, 发回声, 随声附和

idioms:

• echo chamber    回响室
• echo sounder    回波探测器

中文（繁體）(Chinese (Traditional))
n. - 回聲, 回波, 回音
v. tr. - 摹仿, 反射, 重復
v. intr. - 發回聲, 隨聲附和

idioms:

• echo chamber    回響室
• echo sounder    回波探測器

한국어 (Korean)
n. - 메아리, 모방자, 전자파의 반사
v. tr. - 반영하다, 그대로 흉내내다
v. intr. - 메아리치다, 흉내내다

日本語 (Japanese)
n. - エコー, こだま, 繰り返し, 模倣者, 反響
v. - 反響する, 反響させる, 繰り返す

idioms:

• echo chamber    エコールーム, エコーチェンバー
• echo sounder    音響測深器

العربيه (Arabic)
‏(فعل) يكرر, يقلد (الاسم) صدى, ترديد‏

עברית (Hebrew)
n. - ‮הד, הדהוד, תהודה, חקיין, חיקוי, מאורע(ות) הקשור(ים) בעבר‬
v. tr. - ‮חזר כהד, החרה-החזיק אחרי-‬
v. intr. - ‮הדהד‬

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