Echo chamber
Encyclopedia
An echo chamber is a hollow enclosure used to produce echoing
sounds, usually for recording purposes. For example, the producers of a television
or radio
program might wish to produce the aural illusion that a conversation is taking place in a cave; this effect might be accomplished by playing the recording of the conversation inside an echo chamber, with an accompanying microphone
to catch the echoes.
In music, the use of acoustic echo
and reverberation
effects has taken many forms and dates back many hundreds of years. Medieval and Renaissance
sacred music relied heavily on the composers' extensive understanding and use of the complex natural reverberation and echoes inside churches and cathedrals. This early acoustical knowledge informed the design of opera house
s and concert halls in the 17th, 18th and 19th centuries, structures that were deliberately built to create internal echoes in order to enhance and project sound from the stage in the days before electrical amplification. Sometimes echo effects were the unintentional side effect of the architectural or engineering design, such as for the Hamilton Mausoleum
in Scotland, reportedly having the longest echo of any man made building.
and the microphone
— led to the creation of the first artificial echo chambers, built for radio and recording studios. Until the 1950s echo and reverberation were typically created by a combination of electrical and physical methods.
Acoustically speaking, the "classic novel" echo chamber creates echoes in the same way as they are created in churches or caves — they are all simply large enclosed empty spaces with floors and walls made of a hard material (such as polished stone or concrete) that reflect sound waves well. The basic purpose of such chambers is to add colour and depth to the original sound, and to simulate the rich natural reverberation that is a feature of large concert halls.
The development of artificial echo chambers was important for sound recording because of the limitations of early recording systems. Except in the case of live performances, the majority of commercial popular recordings were made in specially constructed studios. These rooms were both heavily insulated to exclude external noises and they were internally anechoic
— that is, they were designed not to produce any internal echoes or reverberation of sound at all.
Because virtually every sound we hear in everyday life is a complex mixture of both the source sound and its echoes and reverberations, audiences not surprisingly found the totally "dry" and echo-free sound of early recordings unappealing. Consequently, record producers and engineers quickly came up with a very effective method of adding "artificial" echo which could, in the hands of experts, be controlled with a remarkable degree of accuracy.
Producing echo and reverberation in this form of echo chamber is remarkably simple. A signal from the studio mixing desk — such as a voice or instrument — is fed to a large high-fidelity loudspeaker
located at one end of the echo chamber. One or more microphones are placed along the length of the room and these pick up both the sound from the speaker and the echoes of it that bounce off the walls of the chamber. The farther away from the speaker, the more echo and reverberation the microphone/s will pick up and the louder the echo becomes in relation to the source. The signal from microphone line is then fed back to the mixing desk, where the echo-enhanced sound can be blended with the original "dry" input.
An example of the use of this physical effect can be heard on the 1978 David Bowie
song "Heroes", from the album of the same name. The song, produced by Tony Visconti
, was recorded in the large concert hall in the Hansa recording studio in Berlin and Visconti has since been much praised for the striking sound he achieved on Bowie's vocals. Visconti placed three microphones at intervals along the length of the hall, one very close to Bowie, one halfway down the hall and the third at the far end of the hall. During the recording, Bowie sang each verse progressively louder than the last and as he increased volume in each verse, Visconti opened up each of the three microphones in turn, from closest to farthest. Thus, in the first verse, Bowie's voice sounds close, warm and present; by the end of the song, Visconti has mixed in a large amount of signal from all three microphones, giving Bowie's voice a strikingly reverberant sound.
The original echo chamber at EMI's Abbey Road Studios
improved by the late Clive Robinson as site foreman at the time of construction, his construction and engineering team perfected the echo booth at Abbey Road Studios, in London it was one of the first in the world to be specially built for recording purposes, when the studio was established in 1931; it remains in place and is a prime example of the early 20th-century electro-acoustic echo chamber.
Buildings such as churches, church halls and ballrooms have often been chosen for the recording of classical and other music because of their rich natural echo and reverberation characteristics. Famous examples include Sir George Martin
's AIR Studios at Lyndhurst Hall in Belsize Park
, London
, a large vaulted 19th century building originally constructed as a church and missionary school. Montreal's Church of St. Eustache is the favoured recording venue of the Montreal Symphony Orchestra and many others, and is much sought after for classical recordings because of its unique acoustic characteristics. Likewise, the distinctive reverberation on the early hit records by Bill Haley & His Comets
was created by recording the band under the domed ceiling of Decca's studio in New York
, located in a former ballroom called The Pythian Temple.
Some recording companies and many small independent labels could not afford large purpose-built echo chambers such as the Abbey Road chamber, so enterprising producers and engineers often made use of any large reverberant space. Corridors, lift-wells, stairwells, tiled bathrooms and toilets were all used as substitute echo chambers. Many famous soul music
and R&B music recordings released by the New York based Atlantic Records
feature echo and reverb effects produced by simply placing a speaker and microphone in the office toilet — a tactic also used by The Doors
for the recording of their 1970 album L.A. Woman
.
In the 1950s and 1960s, the development of magnetic audio tape technology made it possible to duplicate physical echo and reverberation effects entirely electronically. The Watkins Copicat, designed and built by renowned British electronics engineer Charlie Watkins
in the late 1950s, is typical of this kind of electronic delay device.
Tape echo units use an endless loop of magnetic tape, which is drawn across a series of recording and playback heads.
When a signal from a voice or instrument is fed into the machine, it records the signal onto the tape loop as it passed over the record head. As the tape travels on, the newly-recorded signal is then picked up by a series of playback heads mounted in line with the record head. These play the sound back as the signal passes over each head in turn, creating the classic rippling or cascading echoes that are typical of tape echo units.
The number of playback heads determines the number of repeats and the physical distance between each playback head determines the ratio of delay between each repeat of the sound (usually some fraction of a second). The actual length of the delay between each repeat can be varied by a pitch control that alters the speed at which the tape loop moves across the heads.
Typically, the playback heads of tape echo machines are also connected to controls that allow the user to determine the volume of each echo, relative to the original signal. Another control (sometimes called "regeneration") allows the signal from the playback heads to be fed back into and variably mixed with the original input signal, creating a very distinctive "feedback
" effect that adds more and more noise to the loop with each repeat. If fully activated, this control will ultimately produce a continuous feedback loop of pure noise. Roland
manufactured various models of magnetic tape echo and reverb sound effect machines from 1973 until the introduction of digital sound effect machines.
Tape echo that has few repeats and a very short delay between each repeat is often referred to as "slapback" echo. This distinctive sound is one of the key sonic characteristics of 1950s rock and roll
and rockabilly
, and can be heard on the classic mid-50s Sun Records
recordings by Elvis Presley
and others.
With the advent of digital signal processing
and other digital audio
technologies, it became possible to simulate almost every "echo chamber" effect by processing the signal digitally. Because digital devices are able to simulate an almost limitless variety of real reverberant spaces, as well as replicating the classic tape-based echo effects, physical echo chambers fell into disuse. However, as noted above, the use of naturally reverberant spaces such as churches as recording venues continues in classical and other forms of acoustic music.
Invented by Ray Lubow, the "oil-can" method uses a rotating disc made of anodized aluminium, the surface of which is coated with a suspension of carbon particles. An AC signal is sent to a conductive neoprene "wiper", which transfers the high impedance charge to the disc. As the particles pass by the wiper, they act as thousands of tiny capacitors, holding a small part of the charge. A second wiper reads this representation of the signal, and sends it on to a voltage amplifier, where it is mixed with the original source. To protect the charge held in each capacitor and to lubricate the entire assembly, the disc runs inside a sealed can with enough of a special oil (Union Carbide UCON lb65) to assure an even coating is applied as it spins.
The effect resembles an echo, but the whimsical nature of the storage medium causes variations in the sound that can be heard as a vibrato effect. Some early models featured control circuitry designed to feed the output of the read wiper to the write head, causing a reverberant effect as well.
Many different companies marketed these devices under various names. Fender sold the Dimension IV, the Variable Delay, the Echo-Reverb I, II, and III, and included an oilcan in their Special Effects box. Gibson sold the GA-4RE from 1965-7. Ray Lubow himself sold many different versions under the Tel-Ray/Morley brand, starting out in the early sixties with the Ad-n-echo, and eventually producing the Echo-ver-brato, the Electrostatic Delay Line, and many others into the eighties.
Echo (phenomenon)
In audio signal processing and acoustics, an echo 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 and an empty room. A true echo is a single...
sounds, usually for recording purposes. For example, the producers of a television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
or radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
program might wish to produce the aural illusion that a conversation is taking place in a cave; this effect might be accomplished by playing the recording of the conversation inside an echo chamber, with an accompanying microphone
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
to catch the echoes.
In music, the use of acoustic echo
Echo (phenomenon)
In audio signal processing and acoustics, an echo 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 and an empty room. A true echo is a single...
and reverberation
Reverberation
Reverberation is the persistence of sound in a particular space after the original sound is removed. A reverberation, or reverb, is created when a sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air...
effects has taken many forms and dates back many hundreds of years. Medieval and Renaissance
Renaissance
The Renaissance was a cultural movement that spanned roughly the 14th to the 17th century, beginning in Italy in the Late Middle Ages and later spreading to the rest of Europe. The term is also used more loosely to refer to the historical era, but since the changes of the Renaissance were not...
sacred music relied heavily on the composers' extensive understanding and use of the complex natural reverberation and echoes inside churches and cathedrals. This early acoustical knowledge informed the design of opera house
Opera house
An opera house is a theatre building used for opera performances that consists of a stage, an orchestra pit, audience seating, and backstage facilities for costumes and set building...
s and concert halls in the 17th, 18th and 19th centuries, structures that were deliberately built to create internal echoes in order to enhance and project sound from the stage in the days before electrical amplification. Sometimes echo effects were the unintentional side effect of the architectural or engineering design, such as for the Hamilton Mausoleum
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...
in Scotland, reportedly having the longest echo of any man made building.
Electro-acoustic echo chambers
Developments in electronics in the early 20th century — specifically the invention of the amplifierAmplifier
Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...
and the microphone
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
— led to the creation of the first artificial echo chambers, built for radio and recording studios. Until the 1950s echo and reverberation were typically created by a combination of electrical and physical methods.
Acoustically speaking, the "classic novel" echo chamber creates echoes in the same way as they are created in churches or caves — they are all simply large enclosed empty spaces with floors and walls made of a hard material (such as polished stone or concrete) that reflect sound waves well. The basic purpose of such chambers is to add colour and depth to the original sound, and to simulate the rich natural reverberation that is a feature of large concert halls.
The development of artificial echo chambers was important for sound recording because of the limitations of early recording systems. Except in the case of live performances, the majority of commercial popular recordings were made in specially constructed studios. These rooms were both heavily insulated to exclude external noises and they were internally anechoic
Anechoic chamber
An anechoic chamber is a room designed to stop reflections of either sound or electromagnetic waves.They are also insulated from exterior sources of noise...
— that is, they were designed not to produce any internal echoes or reverberation of sound at all.
Because virtually every sound we hear in everyday life is a complex mixture of both the source sound and its echoes and reverberations, audiences not surprisingly found the totally "dry" and echo-free sound of early recordings unappealing. Consequently, record producers and engineers quickly came up with a very effective method of adding "artificial" echo which could, in the hands of experts, be controlled with a remarkable degree of accuracy.
Producing echo and reverberation in this form of echo chamber is remarkably simple. A signal from the studio mixing desk — such as a voice or instrument — is fed to a large high-fidelity loudspeaker
Loudspeaker
A loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...
located at one end of the echo chamber. One or more microphones are placed along the length of the room and these pick up both the sound from the speaker and the echoes of it that bounce off the walls of the chamber. The farther away from the speaker, the more echo and reverberation the microphone/s will pick up and the louder the echo becomes in relation to the source. The signal from microphone line is then fed back to the mixing desk, where the echo-enhanced sound can be blended with the original "dry" input.
An example of the use of this physical effect can be heard on the 1978 David Bowie
David Bowie
David Bowie is an English musician, actor, record producer and arranger. A major figure for over four decades in the world of popular music, Bowie is widely regarded as an innovator, particularly for his work in the 1970s...
song "Heroes", from the album of the same name. The song, produced by Tony Visconti
Tony Visconti
Anthony Edward Visconti is an American record producer and sometimes a musician or singer.Since the late 1960s, he has worked with an array of performers; his lengthiest involvement with any artist is with David Bowie: intermittently from Bowie's 1969 album Space Oddity to 2003's Reality, Visconti...
, was recorded in the large concert hall in the Hansa recording studio in Berlin and Visconti has since been much praised for the striking sound he achieved on Bowie's vocals. Visconti placed three microphones at intervals along the length of the hall, one very close to Bowie, one halfway down the hall and the third at the far end of the hall. During the recording, Bowie sang each verse progressively louder than the last and as he increased volume in each verse, Visconti opened up each of the three microphones in turn, from closest to farthest. Thus, in the first verse, Bowie's voice sounds close, warm and present; by the end of the song, Visconti has mixed in a large amount of signal from all three microphones, giving Bowie's voice a strikingly reverberant sound.
The original echo chamber at EMI's Abbey Road Studios
Abbey Road Studios
Abbey Road Studios is a recording studio located at 3 Abbey Road, St John's Wood, City of Westminster, London, England. It was established in November 1931 by the Gramophone Company, a predecessor of British music company EMI, its present owner...
improved by the late Clive Robinson as site foreman at the time of construction, his construction and engineering team perfected the echo booth at Abbey Road Studios, in London it was one of the first in the world to be specially built for recording purposes, when the studio was established in 1931; it remains in place and is a prime example of the early 20th-century electro-acoustic echo chamber.
Buildings such as churches, church halls and ballrooms have often been chosen for the recording of classical and other music because of their rich natural echo and reverberation characteristics. Famous examples include Sir George Martin
George Martin
Sir George Henry Martin CBE is an English record producer, arranger, composer and musician. He is sometimes referred to as "the Fifth Beatle"— a title that he often describes as "nonsense," but the fact remains that he served as producer on all but one of The Beatles' original albums...
's AIR Studios at Lyndhurst Hall in Belsize Park
Belsize Park
Belsize Park is an area of north-west London, England, in the London Borough of Camden.It is located north-west of Charing Cross and situated on the Northern Line. It borders Hampstead to the north and west, Kentish Town and Gospel Oak to the east, Camden Town to the south east and Primrose Hill...
, London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
, a large vaulted 19th century building originally constructed as a church and missionary school. Montreal's Church of St. Eustache is the favoured recording venue of the Montreal Symphony Orchestra and many others, and is much sought after for classical recordings because of its unique acoustic characteristics. Likewise, the distinctive reverberation on the early hit records by Bill Haley & His Comets
Bill Haley & His Comets
Bill Haley & His Comets was an American rock and roll band that was founded in 1952 and continued until Haley's death in 1981. The band, also known by the names Bill Haley and The Comets and Bill Haley's Comets , was the earliest group of white musicians to bring rock and roll to the attention of...
was created by recording the band under the domed ceiling of Decca's studio in New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
, located in a former ballroom called The Pythian Temple.
Some recording companies and many small independent labels could not afford large purpose-built echo chambers such as the Abbey Road chamber, so enterprising producers and engineers often made use of any large reverberant space. Corridors, lift-wells, stairwells, tiled bathrooms and toilets were all used as substitute echo chambers. Many famous soul music
Soul music
Soul music is a music genre originating in the United States combining elements of gospel music and rhythm and blues. According to the Rock and Roll Hall of Fame, soul is "music that arose out of the black experience in America through the transmutation of gospel and rhythm & blues into a form of...
and R&B music recordings released by the New York based Atlantic Records
Atlantic Records
Atlantic Records is an American record label best known for its many recordings of rhythm and blues, rock and roll, and jazz...
feature echo and reverb effects produced by simply placing a speaker and microphone in the office toilet — a tactic also used by The Doors
The Doors
The Doors were an American rock band formed in 1965 in Los Angeles, California, with vocalist Jim Morrison, keyboardist Ray Manzarek, drummer John Densmore, and guitarist Robby Krieger...
for the recording of their 1970 album L.A. Woman
L.A. Woman
The band embarked on a tour to promote the album, although it would only comprise two dates. The first was held in Dallas, Texas on December 11 and reportedly went well. The second performance took place at The Warehouse in New Orleans, Louisiana, on December 12, 1970, where Morrison apparently had...
.
Electronic echo chambers and echo machines
Charlie Watkins (audio engineer)
Charlie Watkins is a British audio engineer and musical instrument maker, and is notable for pioneering loud PA systems for outdoor rock festivals...
in the late 1950s, is typical of this kind of electronic delay device.
Tape echo units use an endless loop of magnetic tape, which is drawn across a series of recording and playback heads.
When a signal from a voice or instrument is fed into the machine, it records the signal onto the tape loop as it passed over the record head. As the tape travels on, the newly-recorded signal is then picked up by a series of playback heads mounted in line with the record head. These play the sound back as the signal passes over each head in turn, creating the classic rippling or cascading echoes that are typical of tape echo units.
The number of playback heads determines the number of repeats and the physical distance between each playback head determines the ratio of delay between each repeat of the sound (usually some fraction of a second). The actual length of the delay between each repeat can be varied by a pitch control that alters the speed at which the tape loop moves across the heads.
Typically, the playback heads of tape echo machines are also connected to controls that allow the user to determine the volume of each echo, relative to the original signal. Another control (sometimes called "regeneration") allows the signal from the playback heads to be fed back into and variably mixed with the original input signal, creating a very distinctive "feedback
Feedback
Feedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or...
" effect that adds more and more noise to the loop with each repeat. If fully activated, this control will ultimately produce a continuous feedback loop of pure noise. Roland
Roland RE-201
The Roland RE-201, commonly known as the Space Echo, is an audio analog delay effects unit produced by the Roland Corporation.A tape echo device records incoming audio to a loop of magnetic tape, then replays the audio over a series of several playback heads before it is erased again by new...
manufactured various models of magnetic tape echo and reverb sound effect machines from 1973 until the introduction of digital sound effect machines.
Tape echo that has few repeats and a very short delay between each repeat is often referred to as "slapback" echo. This distinctive sound is one of the key sonic characteristics of 1950s rock and roll
Rock and roll
Rock and roll is a genre of popular music that originated and evolved in the United States during the late 1940s and early 1950s, primarily from a combination of African American blues, country, jazz, and gospel music...
and rockabilly
Rockabilly
Rockabilly is one of the earliest styles of rock and roll music, dating to the early 1950s.The term rockabilly is a portmanteau of rock and hillbilly, the latter a reference to the country music that contributed strongly to the style's development...
, and can be heard on the classic mid-50s Sun Records
Sun Records
Sun Records is a record label founded in Memphis, Tennessee, starting operations on March 27, 1952.Founded by Sam Phillips, Sun Records was known for giving notable musicians such as Elvis Presley , Carl Perkins, Roy Orbison, and Johnny Cash...
recordings by Elvis Presley
Elvis Presley
Elvis Aaron Presley was one of the most popular American singers of the 20th century. A cultural icon, he is widely known by the single name Elvis. He is often referred to as the "King of Rock and Roll" or simply "the King"....
and others.
Digital echo
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
and other digital audio
Digital audio
Digital audio is sound reproduction using pulse-code modulation and digital signals. Digital audio systems include analog-to-digital conversion , digital-to-analog conversion , digital storage, processing and transmission components...
technologies, it became possible to simulate almost every "echo chamber" effect by processing the signal digitally. Because digital devices are able to simulate an almost limitless variety of real reverberant spaces, as well as replicating the classic tape-based echo effects, physical echo chambers fell into disuse. However, as noted above, the use of naturally reverberant spaces such as churches as recording venues continues in classical and other forms of acoustic music.
Oil-can delay method
An alternative echo system was the so-called "oil-can delay" method, which uses electrostatic rather than electromagnetic recording.Invented by Ray Lubow, the "oil-can" method uses a rotating disc made of anodized aluminium, the surface of which is coated with a suspension of carbon particles. An AC signal is sent to a conductive neoprene "wiper", which transfers the high impedance charge to the disc. As the particles pass by the wiper, they act as thousands of tiny capacitors, holding a small part of the charge. A second wiper reads this representation of the signal, and sends it on to a voltage amplifier, where it is mixed with the original source. To protect the charge held in each capacitor and to lubricate the entire assembly, the disc runs inside a sealed can with enough of a special oil (Union Carbide UCON lb65) to assure an even coating is applied as it spins.
The effect resembles an echo, but the whimsical nature of the storage medium causes variations in the sound that can be heard as a vibrato effect. Some early models featured control circuitry designed to feed the output of the read wiper to the write head, causing a reverberant effect as well.
Many different companies marketed these devices under various names. Fender sold the Dimension IV, the Variable Delay, the Echo-Reverb I, II, and III, and included an oilcan in their Special Effects box. Gibson sold the GA-4RE from 1965-7. Ray Lubow himself sold many different versions under the Tel-Ray/Morley brand, starting out in the early sixties with the Ad-n-echo, and eventually producing the Echo-ver-brato, the Electrostatic Delay Line, and many others into the eighties.
See also
- Reverberation roomReverberation roomA reverberation chamber or room is a room designed to create a diffuse or random incidence sound field . Reverberation chambers tend to be large rooms and have very hard exposed surfaces...
An echo chamber for scientific measurement (Acoustics) - Anechoic chamberAnechoic chamberAn anechoic chamber is a room designed to stop reflections of either sound or electromagnetic waves.They are also insulated from exterior sources of noise...
- Telephone game
- R.G. Keen: The Technology of Oil Can Delays http://www.geofex.com/Article_Folders/oil_can_delays.htm
- Bathroom singingBathroom singingBathroom singing, also known as singing in the bathroom, singing in the bath, or singing in the shower is a widespread phenomenon....