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{{Short description|Voice encryption, transformation, and synthesis device}}
{{About|the voice encoder|the dictation machine|Voice recorder|speech synthesis|Voder}}

[[File:Kraftwerk Vocoder custom made in early1970s.JPG|upright=1.15|Early 1970s vocoder, custom-built for electronic music band [[Kraftwerk]]|right|thumb]]

A '''vocoder''' ({{IPAc-en|ˈ|v|oʊ|k|oʊ|d|ər}}, a [[portmanteau]] of ''vo''ice and en''coder'') is a [[Speech coding#Categories|category]] of [[speech coding]] that analyzes and [[Speech synthesis|synthesizes]] the human voice signal for [[audio data compression]], [[multiplexing]], [[voice encryption]] or voice transformation.

The vocoder was invented in 1938 by [[Homer Dudley]] at [[Bell Labs]] as a means of synthesizing human speech.<ref>{{Cite patent|title=System for the artificial production of vocal or other sounds|gdate=1937-04-07|url=https://patents.google.com/patent/US2121142A/en |country=US |number=135416A}}</ref> This work was developed into the '''channel vocoder''' which was used as a voice [[codec]] for [[telecommunications]] for speech coding to conserve [[bandwidth (computing)|bandwidth]] in transmission.

By [[encrypting]] the control signals, voice transmission can be secured against interception. Its primary use in this fashion is for secure radio communication. The advantage of this method of encryption is that none of the original signal is sent, only envelopes of the bandpass filters. The receiving unit needs to be set up in the same filter configuration to re-synthesize a version of the original signal spectrum.

The vocoder has also been used extensively as an [[electronic musical instrument]]. The decoder portion of the vocoder, called a [[voder]], can be used independently for speech synthesis.

==Theory==
{{Unreferenced section|date=July 2019}}

The [[human voice]] consists of sounds generated by the periodic opening and closing of the [[glottis]] by the [[vocal cords]], which produces an acoustic waveform with many [[harmonic]]s. This initial sound is then [[Audio filter|filter]]ed by movements in the nose, mouth and throat (a complicated [[resonant]] piping system known as the [[vocal tract]]) to produce fluctuations in harmonic content ([[formant]]s) in a controlled way, creating the wide variety of sounds used in speech. There is another set of sounds, known as the [[unvoiced]] and [[plosive]] sounds, which are created or modified by a variety of sound-generating disruptions of airflow occurring in the [[vocal tract]].

The vocoder analyzes speech by measuring how its [[spectral energy distribution]] characteristics fluctuate across time. This analysis results in a set of temporally parallel [[Envelope (waves)|envelope]] signals, each representing the individual [[frequency band]] amplitudes of the user's speech. Put another way, the voice signal is divided into a number of [[frequency bands]] (the larger this number, the more accurate the analysis) and the level of signal present at each frequency band, occurring simultaneously, measured by an [[envelope follower]], represents the spectral energy distribution across time. This set of envelope amplitude signals is called the [[Modulation|"modulator"]]. 
To recreate speech, the vocoder reverses the analysis process, variably filtering an initial broadband noise (referred to alternately as the "source" or "carrier"), by passing it through a set of [[band-pass filter]]s, whose individual envelope amplitude levels are controlled, in real time, by the set of analyzed envelope amplitude signals from the modulator.

The digital encoding process involves a periodic analysis of each of the modulator's multiband set of filter envelope amplitudes. This analysis results in a set of digital [[pulse code modulation]] stream readings. Then the pulse code modulation stream outputs of each band are transmitted to a decoder. The decoder applies the pulse code modulations as control signals to the corresponding amplifiers of the output filter channels.

Information about the [[fundamental frequency]] of the initial voice signal (as distinct from its spectral characteristic) is discarded; it was not important to preserve this for the vocoder's original use as an encryption aid. It is this dehumanizing aspect of the vocoding process that has made it useful in creating special voice effects in popular music and audio entertainment.

Instead of a point-by-point recreation of the waveform, the vocoder process sends only the parameters of the vocal model over the communication link. Since the parameters change slowly compared to the original speech waveform, the bandwidth required to transmit speech can be reduced. This allows more speech channels to utilize a given [[communication channel]], such as a radio channel or a [[Submarine communications cable|submarine cable]].

Analog vocoders typically analyze an incoming signal by splitting the signal into multiple tuned frequency bands or ranges. To reconstruct the signal, a [[carrier signal]] is sent through a series of these tuned band-pass filters. In the example of a typical robot voice the carrier is noise or a [[sawtooth waveform]]. There are usually between 8 and 20 bands.

The amplitude of the modulator for each of the individual analysis bands generates a voltage that is used to control amplifiers for each of the corresponding carrier bands. The result is that frequency components of the modulating signal are mapped onto the carrier signal as discrete amplitude changes in each of the frequency bands.

Often there is an unvoiced band or [[sibilance]] channel. This is for frequencies that are outside the analysis bands for typical speech but are still important in speech. Examples are words that start with the letters ''s'', ''f'', ''ch'' or any other sibilant sound. Using this band produces recognizable speech, although somewhat mechanical sounding. Vocoders often include a second system for generating unvoiced sounds, using a [[noise generator]] instead of the fundamental frequency. This is mixed with the carrier output to increase clarity.

In the channel vocoder algorithm, among the two components of an [[analytic signal]], considering only the [[amplitude]] component and simply ignoring the [[instantaneous phase|phase]] component tends to result in an unclear voice; on methods for rectifying this, see [[phase vocoder]].

==History==
[[Image:Homer Dudley (October 1940). "The Carrier Nature of Speech". Bell System Technical Journal, XIX(4);495-515. -- Fig.7 Schematic circuit of the vocoder (derived from Fig.8).jpg|thumb|upright=1.35|Schematic circuit of Dudley's Vocoder<br />(based on: {{harvnb|Dudley|1940|p=[https://archive.org/stream/bellsystemtechni19amerrich/bellsystemtechni19amerrich#page/508/mode/1up 508]|loc=Fig.7<!-- Schematic circuit of the vocoder -->}}<ref>
  {{cite journal
   | first     = Homer | last = Dudley
   | date      = October 1940
   | title     = The Carrier Nature of Speech
   | url       = https://archive.org/stream/bellsystemtechni19amerrich/bellsystemtechni19amerrich#page/495/mode/1up
   | journal   = Bell System Technical Journal
   | volume    = XIX | issue = 4
  }}</ref>)]]
{{multiple image
| align             = right
| direction         = horizontal
| total_width       = 310
| image1            = SIGSALY.jpg
| caption1          = SIGSALY (1943–1946) speech encipherment system
| image2            = HY-2 VOCODER.jpg
| caption2          = HY-2 Vocoder (designed in 1961) was the last generation of channel vocoder in the [[US]].<ref name="cryptomuseum">{{cite web|url=https://www.cryptomuseum.com/crypto/usa/hy2/index.htm |title=HY-2 |publisher=Cryptomuseum.com |access-date=2019-07-31}}</ref><ref name="jproc">
  {{cite web
   | title     = HY-2 Vocoder
   | url       = http://jproc.ca/crypto/hy02.html
   | publisher = Crypto Machines
  }}</ref>
}}

The development of a vocoder was started in 1928 by [[Bell Labs]] engineer [[Homer Dudley]],<ref name=autogenerated>{{cite journal|author=Mills, Mara|year=2012|title=Media and Prosthesis: the Vocoder, the Artificial Larynx, and the History of Signal Processing|journal=Qui Parle |volume=21|issue=1|pages= 107–149|url=https://muse.jhu.edu/article/491050/summary|doi=10.5250/quiparle.21.1.0107|s2cid=143012886|url-access=subscription}}
</ref> who was granted patents for it on March 21, 1939,<ref name="USpatentapplication2151019">
{{cite patent
 | country = US
 | number = 2151091
 | status = application
 | title = [https://patents.google.com/patent/US2151091 Signal Transmission]
 | pubdate = May 21, 1939
 | gdate =
 | fdate = October 30, 1935
 | pridate =
 | inventor = Dudley, Homer W.
 | invent1 =
 | invent2 =
 | assign1 = [[Bell Telephone Laboratories]], Inc.
 | assign2 =
 | class =
}} (filed October 30, 1935)
</ref> and Nov 16, 1937.<ref name="USpatentapplication2098956">
{{cite patent
 | country = US
 | number = 2098956
 | status = application
 | title = [https://patents.google.com/patent/US2098956 Signaling system]
 | pubdate = 1937-11-16
 | gdate =
 | fdate = 1936-12-03
 | pridate =
 | inventor = Dudley, Homer W.
 | invent1 =
 | invent2 =
 | assign1 = [[Bell Telephone Laboratories]], Inc.
 | assign2 =
 | class =
}}
</ref>

To demonstrate the [[speech synthesis]] ability of its decoder section, the [[voder]] (voice operating demonstrator)<ref name=USpatentapplication2121142>
{{cite patent
 | country = US
 | number = 2121142
 | status = apprication
 | title = [https://patents.google.com/patent/US2121142 Signal Transmission]
 | pubdate = 1938-06-21
 | gdate =
 | fdate = 1937-04-07
 | pridate =
 | inventor = Dudley, Homer
 | invent1 =
 | invent2 =
 | assign1 = [[Bell Telephone Laboratories]], Inc.
 | assign2 =
 | class =
}}
</ref> was introduced to the public at the AT&T building at the 1939–1940 New York World's Fair.<ref name="120years-HomerDudley">{{cite web|url=http://120years.net/the-voder-vocoderhomer-dudleyusa1940/|title=The 'Voder' & 'Vocoder' Homer Dudley, USA, 1940|date=2013-09-21|work=120 Years of Electronic Music (120years.net)|quote=The Vocoder (Voice Operated reCorDER) and Voder (Voice Operation DEmonstratoR) developed by the research physicist Homer Dudley, ... The Voder was first unveiled in 1939 at the New York World Fair (where it was demonstrated at hourly intervals) and later in 1940 in San Francisco. There were twenty trained operators known as the 'girls' who handled the machine much like a musical instrument such as a piano or an organ, ... This was done by manipulating fourteen keys with the fingers, a bar with the left wrist and a foot pedal with the right foot.}}</ref> The voder consisted of an [[electronic oscillator]]{{snd}} a sound source of [[pitch (sound)|pitched]] tone{{snd}} and [[noise generator]] for [[noise (audio)|hiss]], a 10-band [[band-pass filter|resonator filters]] with [[variable-gain amplifier]]s as a [[vocal tract]], and the manual controllers including a set of pressure-sensitive keys for filter control, and a [[Expression pedal|foot pedal]] for [[pitch control]] of tone.<ref name=haskinsLabs>{{cite web
 | title     = The Voder (1939)
 | url     = http://www.haskins.yale.edu/featured/heads/SIMULACRA/voder.html
 | work     = Talking Heads: Simulacra
 | publisher     = [[Haskins Laboratories]]
 | access-date     = 2015-08-27
 | archive-date     = 2015-09-24
 | archive-url     = https://web.archive.org/web/20150924025249/http://www.haskins.yale.edu/featured/heads/SIMULACRA/voder.html
 | url-status     = dead
 }} Based on {{cite book
 | author    = James L. Flanagan
 | chapter   = Speech Synthesis
 | title     = Speech Analysis, Synthesis and Perception
 | publisher = Springer-Verlag
 | date      = 1965
 | pages     = 172–173
}} (See [http://www.haskins.yale.edu/featured/heads/SIMULACRA/graphics/voder.gif schematic diagram of the Voder synthesizer] {{Webarchive|url=https://web.archive.org/web/20150924025247/http://www.haskins.yale.edu/featured/heads/SIMULACRA/graphics/voder.gif |date=2015-09-24 }}.)</ref> The filters controlled by keys convert the tone and the hiss into [[vowel]]s, [[consonant]]s, and [[inflection]]s. This was a complex machine to operate, but a skilled operator could produce recognizable speech.<ref name="120years-HomerDudley"/><ref group=media>
{{cite AV media
 | title     = One Of The First Vocoder Machine [sic]
 | url       = https://www.youtube.com/watch?v=mSdFu1xdoZk
 | medium    = Motion picture
 | date      = c. 1939
}} A demonstration of the [[voder]] (not the vocoder).
</ref>

Dudley's vocoder was used in the [[SIGSALY]] system, which was built by Bell Labs engineers in 1943. SIGSALY was used for encrypted voice communications during [[World War&nbsp;II]]. The KO-6 voice coder was released in 1949 in limited quantities; it was a close approximation to the SIGSALY at {{nowrap|1200 bit/s}}. In 1953, KY-9 THESEUS<ref>{{cite web |url=https://www.cryptomuseum.com/crypto/usa/ky9/index.htm |title=KY-9 |publisher=Cryptomuseum.com |access-date=2019-07-31}}</ref> {{nowrap|1650 bit/s}} voice coder used solid-state logic to reduce the weight to {{convert|565|lbs|kg}} from SIGSALY's {{convert|55|ST|kg}}, and in 1961 the HY-2 voice coder, a 16-channel {{nowrap|2400 bit/s}} system, weighed {{convert|100|lbs|kg}} and was the last implementation of a channel vocoder in a secure speech system.<ref>{{cite web |url=https://www.nsa.gov/Portals/70/documents/about/cryptologic-heritage/historical-figures-publications/publications/wwii/sigsaly_history.pdf |title=Campbell.qxd |access-date=2019-07-31}}</ref>

Later work in this field has since used digital [[speech coding]]. The most widely used speech coding technique is [[linear predictive coding]] (LPC).<ref>{{cite journal |last1=Gupta |first1=Shipra |title=Application of MFCC in Text Independent Speaker Recognition |journal=International Journal of Advanced Research in Computer Science and Software Engineering |date=May 2016 |volume=6 |issue=5 |pages=805–810 (806) |s2cid=212485331 |issn=2277-128X |url=https://pdfs.semanticscholar.org/2aa9/c2971342e8b0b1a0714938f39c406f258477.pdf |archive-url=https://web.archive.org/web/20191018231621/https://pdfs.semanticscholar.org/2aa9/c2971342e8b0b1a0714938f39c406f258477.pdf |url-status=dead |archive-date=2019-10-18 |access-date=18 October 2019 |quote=LPC methods are the most widely used in speech coding}}</ref> Another speech coding technique, [[adaptive differential pulse-code modulation]] (ADPCM), was developed by P.&nbsp;Cummiskey, [[Nikil Jayant|Nikil S.&nbsp;Jayant]] and [[James L.&nbsp;Flanagan]] at Bell Labs in 1973.<ref>{{cite journal |last1=Cummiskey |first1=P. |last2=Jayant |first2=Nikil S. |author2-link=Nikil Jayant |last3=Flanagan |first3=James L. |author3-link=James L. Flanagan |title=Adaptive quantization in differential PCM coding of speech |journal=[[The Bell System Technical Journal]] |date=1973 |volume=52 |issue=7 |pages=1105–1118 |doi=10.1002/j.1538-7305.1973.tb02007.x}}</ref>

==Applications==
* Terminal equipment for systems based on [[digital mobile radio]] (DMR).
* Digital voice scrambling and encryption
* [[Cochlear implant]]s: noise and tone vocoding is used to simulate the effects of cochlear implants.<ref>{{Cite journal |last=Aguiar |first=Daniel E. |last2=Taylor |first2=N. Ellen |last3=Li |first3=Jing |last4=Gazanfari |first4=Daniel K. |last5=Talavage |first5=Thomas M. |last6=Laflen |first6=J. Brandon |last7=Neuberger |first7=Heidi |last8=Svirsky |first8=Mario A. |date=2016-03-01 |title=Information theoretic evaluation of a noiseband-based cochlear implant simulator |url=https://www.sciencedirect.com/science/article/abs/pii/S0378595515001963 |journal=Hearing Research |volume=333 |pages=185–193 |doi=10.1016/j.heares.2015.09.008 |issn=0378-5955|pmc=4798893 }}</ref>
* Musical and other artistic effects<ref>[[Ernst Rothauser]]. Dissertation and patents on vocoder technology.</ref>

==Modern implementations==
{{See also|Speech codec|Audio codec}}

Even with the need to record several frequencies and additional unvoiced sounds, the compression of vocoder systems is impressive. Standard speech-recording systems capture frequencies from about 500 to 3,400&nbsp;Hz, where most of the frequencies used in speech lie, typically using a sampling rate of 8&nbsp;kHz (slightly greater than the [[Nyquist rate]]). The sampling resolution is typically 8 or more bits per sample, for a data rate in the range of {{nowrap|64 kbit/s}}, but a good vocoder can provide a reasonably good simulation of voice with as little as {{nowrap|5 kbit/s}} of data.

''Toll quality'' voice coders, such as ITU [[G.729]], are used in many telephone networks. G.729 in particular has a final data rate of {{nowrap|8 kbit/s}} with superb voice quality. G.723 achieves slightly worse quality at data rates of 5.3 and {{nowrap|6.4 kbit/s}}. Many voice vocoder systems use lower data rates, but below {{nowrap|5 kbit/s}} voice quality begins to drop rapidly.{{citation needed|date=January 2023}}

Several vocoder systems are used in [[NSA encryption systems]]:
* LPC-10, [[Federal Information Processing Standard|FIPS]] Pub 137, {{nowrap|2400 bit/s}}, which uses [[linear predictive coding]]
* [[Code-excited linear prediction]] (CELP), 2400 and {{nowrap|4800 bit/s}}, Federal Standard 1016, used in [[STU-III]]
* [[Continuously variable slope delta modulation]] (CVSD), {{nowrap|16 kbit/s}}, used in wide band encryptors such as the KY-57.
* [[Mixed-excitation linear prediction]] (MELP), MIL STD 3005, {{nowrap|2400 bit/s}}, used in the Future Narrowband Digital Terminal [[FNBDT]], [[NSA]]'s 21st century secure telephone.
* [[Adaptive Differential Pulse Code Modulation]] (ADPCM), former [[ITU-T]] G.721, {{nowrap|32 kbit/s}} used in [[Secure Terminal Equipment|STE]] secure telephone{{efn|ADPCM is not a proper vocoder but rather a waveform codec. [[ITU]] has gathered G.721 along with some other ADPCM codecs into G.726.}}

Modern vocoders that are used in communication equipment and in voice storage devices today are based on the following algorithms:
* [[Algebraic code-excited linear prediction]] (ACELP 4.7–24&nbsp;kbit/s)<ref>
 {{cite web
  | title     = Voice Age
  | url       = http://www.voiceage.com/codecs.php
  | format    = licensing
  | publisher = VoiceAge Corporation
 }}</ref>
* [[Mixed-excitation linear prediction]] (MELPe 2400, 1200 and {{nowrap|600 bit/s}})<ref>
 {{cite web
  | title     = <!-- Compandent -->MELPe – FAQ
  | url       = http://www.compandent.com/melpe_faq.htm
  | publisher = Compandent Inc
 }}</ref>
* [[Multi-band excitation]] (AMBE {{nowrap|2000 bit/s}}&nbsp;– {{nowrap|9600 bit/s}})<ref>{{cite web
  | title     = IMBE and AMBE
  | url     = http://dvsinc.com/papers/iambe.htm
  | publisher     = Digital Voice Systems, Inc.
  | access-date     = 2008-11-08
  | archive-date     = 2017-07-07
  | archive-url     = https://web.archive.org/web/20170707231905/http://www.dvsinc.com/papers/iambe.htm
  | url-status     = dead
  }}</ref>
* Sinusoidal-Pulsed Representation (SPR {{nowrap|600 bit/s}}&nbsp;– {{nowrap|4800 bit/s}})<ref>{{cite web
  | title     = SPR Vocoders
  | url     = https://dspini.com/
  | publisher     = DSP Innovations Inc.
  | access-date     = 2008-11-08
  | archive-date     = 2009-01-30
  | archive-url     = https://web.archive.org/web/20090130084346/http://dspini.com/
  | url-status     = dead
  }}</ref>
* Robust Advanced Low-complexity Waveform Interpolation (RALCWI 2050, 2400 and {{nowrap|2750 bit/s}})<ref>{{cite web
  | title     = RALCWI Vocoder IC's
  | url     = http://www.cmlmicro.com/products/CMX608-618-638_RALCWI_Vocoder/
  | work     = CML Microcircuits
  | publisher     = CML Microsystems Plc
  | access-date     = 2013-05-17
  | archive-date     = 2018-03-15
  | archive-url     = https://web.archive.org/web/20180315114843/http://www.cmlmicro.com/products/CMX608-618-638_RALCWI_Vocoder/
  | url-status     = dead
  }}</ref>
* Tri-Wave Excited Linear Prediction (TWELP 300–9600&nbsp;bit/s)<ref>
 {{cite web
  | title     = TWELP Vocoder
  | url       = https://dspini.com
  | publisher = DSP Innovations Inc
 }}</ref>
* Noise Robust Vocoder (NRV 300 and {{nowrap|800 bit/s}})<ref>
 {{cite web
  | title     = Noise Rubust Vocoders<!-- 300-800bit/s from BBN -->
  | url       = http://www.bbn.com/technology/speech/nrv
  | publisher = Raytheon BBN Technologies
  | archive-url= https://web.archive.org/web/20140402124332/http://bbn.com/technology/speech/nrv
  | archive-date=2014-04-02
 }}</ref>

Vocoders are also currently used in [[psychophysics]], [[linguistics]], [[computational neuroscience]] and [[cochlear implant]] research.

===Linear prediction-based===
{{Further|Linear predictive coding}}

Since the late 1970s, most non-musical vocoders have been implemented using [[linear prediction]], whereby the target signal's spectral envelope (formant) is estimated by an all-pole [[Infinite impulse response|IIR]] [[digital filter|filter]]. In linear prediction coding, the all-pole filter replaces the bandpass filter bank of its predecessor and is used at the encoder to ''whiten'' the signal (i.e., flatten the spectrum) and again at the decoder to re-apply the spectral shape of the target speech signal.

One advantage of this type of filtering is that the location of the linear predictor's spectral peaks is entirely determined by the target signal and can be as precise as allowed by the time period to be filtered. This is in contrast with vocoders realized using fixed-width filter banks, where the location of spectral peaks is constrained by the available fixed frequency bands. LP filtering also has disadvantages in that signals with a large number of constituent frequencies may exceed the number of frequencies that can be represented by the linear prediction filter. This restriction is the primary reason that LP coding is almost always used in tandem with other methods in high-compression voice coders.

===Waveform-interpolative===
Waveform-interpolative (WI) vocoder was developed at [[AT&T Bell Laboratories]] around 1995 by W.B. Kleijn, and subsequently, a low-complexity version was developed by AT&T for the DoD secure vocoder competition.  Notable enhancements to the WI coder were made at the [[University of California, Santa Barbara]].  AT&T holds the core patents related to WI and other institutes hold additional patents.<ref name="kleijn95">
{{cite book
 | last1     = Kleijn | first1 = W.B.
 | last2     = Haagen | first2 = J.
 | others    = (AT&T Bell Labs., Murray Hill, NJ)
 | chapter     = A speech coder based on decomposition of characteristic waveforms
 | doi       = 10.1109/ICASSP.1995.479640
| title = 1995 International Conference on Acoustics, Speech, and Signal Processing
 | volume = 1
 | pages = 508–511
 | year = 1995
 | isbn = 978-0-7803-2431-2
 | s2cid = 9105323
 }}</ref><ref name="kleijn96">
{{cite conference
 | last1      = Kleijn | first1 = W.B.
 | last2     = Shoham | first2 = Y.
 | last3     = Sen    | first3 = D.
 | last4     = Hagen  | first4 = R.
 | others    = (AT&T Bell Labs., Murray Hill, NJ)
 | chapter     = A low-complexity waveform interpolation coder
 | conference = [[International Conference on Acoustics, Speech, and Signal Processing]]
 | doi       = 10.1109/ICASSP.1996.540328
 | title = 1996 IEEE International Conference on Acoustics, Speech, and Signal Processing Conference Proceedings
 | volume = 1
 | pages = 212–215
 | year = 1996
 | isbn = 978-0-7803-3192-1
 | s2cid = 44346744
 }}</ref><ref name="gottesman01">
{{cite journal
 | last1     = Gottesman | first1 = O.
 | last2     = Gersho    | first2 = A.
 | others    = (Dept. of Electr. & Comput. Eng., California Univ., Santa Barbara, CA)
 | title     = Enhanced waveform interpolative coding at low bit-rate
 | journal   = IEEE Transactions on Speech and Audio Processing
 | volume = 9
 | issue     = November 2001
 | pages = 786–798
 | doi       = 10.1109/89.966082
| year = 2001
 | s2cid = 17949435
 }}</ref>

==Artistic effects==
===Uses in music===
[[File:Vocoder.PNG|thumb|Channel vocoder setting as a musical application; the Dutch captions are "Band-pass filters" and "Level meters".]]

For [[music]]al applications, a source of musical sounds is used as the carrier, instead of extracting the fundamental frequency. For instance, one could use the sound of a [[synthesizer]] as the input to the filter bank, a technique that became popular in the 1970s.

====History====
[[Werner Meyer-Eppler]], a German scientist with a special interest in electronic voice synthesis, published a thesis in 1948 on [[electronic music]] and [[speech synthesis]] from the viewpoint of [[sound synthesis]].<ref name="meyer-eppler1949">{{citation
 | last      = Meyer-Eppler | first = Werner
 | author-link= Werner Meyer-Eppler
 | year      = 1949
 | title     = Elektronische Klangerzeugung: Elektronische Musik und synthetische Sprache
 | location  = Bonn
 | publisher = Ferdinand Dümmlers
}}</ref> Later he was instrumental in the founding of the [[Studio for Electronic Music (WDR)|Studio for Electronic Music]] of [[Westdeutscher Rundfunk|WDR]] in Cologne, in 1951.<ref name="meyer-eppler">{{citation
 | first    = Sonja| last    = Diesterhöft
 | year      = 2003
 | title     = Meyer-Eppler und der Vocoder
 | url       = http://www.kgw.tu-berlin.de/statisch/Studio/Meyer-Eppler/Meyer-Eppler.html
 | work      = Seminars Klanganalyse und -synthese
 | language  = de
 | publisher = Fachgebiet Kommunikationswissenschaft, [[:de:Technische Universität Berlin#Geisteswissenschaften|Institut für Sprache und Kommunikation, Technische Universität Berlin]]
 | archive-url = https://web.archive.org/web/20080305021509/http://www.kgw.tu-berlin.de/statisch/Studio/Meyer-Eppler/Meyer-Eppler.html
 | archive-date = 2008-03-05
}}</ref>

[[File:Siemens Tonstudio, Deutsches Museum.jpg|thumb|Siemens Synthesizer ({{circa|1959}}) at [[Siemens]] Studio for Electronic Music was one of the first attempts to use a vocoder (rear) to create music.]]
One of the first attempts to use a vocoder in creating music was the ''Siemens Synthesizer'' at the Siemens Studio for Electronic Music, developed between 1956 and 1959.<ref name="siemens">{{cite web
 |title       = Das Siemens-Studio für elektronische Musik von Alexander Schaaf und Helmut Klein
 |url         = http://www.deutsches-museum.de/sammlungen/ausgewaehlte-objekte/meisterwerke-vi/siemens-studio/
 |language    = de
 |publisher   = Deutsches Museum
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20130930175905/http://www.deutsches-museum.de/sammlungen/ausgewaehlte-objekte/meisterwerke-vi/siemens-studio
 |archive-date = 2013-09-30
}}</ref><ref name=holmes2012>{{cite book
 | last      = Holmes | first = Thom
 | chapter   = Early Synthesizers and Experimenters
 | chapter-url= https://books.google.com/books?id=aT5nAQAAQBAJ&pg=PA190
 | title     = Electronic and Experimental Music: Technology, Music, and Culture
 | edition   = 4th
 | publisher = Routledge
 | date = 2012
 | isbn     = 978-1-136-46895-7
 | pages     =  190–192
}} (See also excerpt of pp. <!--
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 -->from the [https://books.google.com/books?id=hCthQ-bec-QC 3rd edition in 2008] <!--
 -->({{ISBN|978-0-415-95781-6}}))</ref><ref group=media>{{cite AV media
 | title     = Siemens Electronic Music Studio in Deutsches Museum (multi part)
 | url       = https://www.youtube.com/watch?v=9F7wP9dz5IY&list=PL84027969B66FECBD&index=2
 | medium    = Video
}}&nbsp; Details of the Siemens Electronic Music Studio, exhibited at the [[Deutsches Museum]].</ref>

In 1968, [[Robert Moog]] developed one of the first [[Solid state (electronics)|solid-state]] musical vocoders for the electronic music studio of the [[University at Buffalo]].<ref name=bode1984>{{cite journal
 | last      = Bode | first = Harald
 | author-link= Harald Bode
 | title     = History of Electronic Sound Modification
 | journal   = [[Journal of the Audio Engineering Society]]
 | volume    = 32 | issue = 10 | pages = 730–739
 | date      = October 1984 |url=http://www.vasulka.org/archive/Artists1/Bode,Harald/History.pdf
}}</ref>

In 1968, [[Bruce Haack]] built a prototype vocoder, named ''Farad'' after [[Michael Faraday]].<ref name="farad">{{cite AV media notes
 | others    = Bruce Haack
 | year      = 2010
 | title     = BRUCE HAACK&nbsp;– FARAD: THE ELECTRIC VOICE
 | url       = http://www.stonesthrow.com/news/2010/07/stones-throw-bruce-haack-vocoder
 | publisher = Stones Throw Records LLC
}}</ref>  It was first featured on "The Electronic Record For Children" released in 1969 and then on his rock album ''[[The Electric Lucifer]]'' released in 1970.<ref name="brucehaack">{{cite web
 | title     = Bruce Haack's Biography 1965–1974
 | url     = http://www.brucehaack.com/biography/biography-1965-1974
 | publisher     = Bruce Haack Publishing
 | access-date     = 2013-05-03
 | archive-date     = 2013-02-09
 | archive-url     = https://web.archive.org/web/20130209201207/http://www.brucehaack.com/biography/biography-1965-1974
 | url-status     = dead
 }}</ref><ref group=media>{{cite AV media
 | people    = Bruce Haack
 | date = 1970
 | title     = Electric to Me Turn&nbsp;– from "The Electric Lucifer"
 | url       = https://www.youtube.com/watch?v=t7BCyF3xiY0
 | medium    = Phonograph
 | publisher = Columbia Records
}} &nbsp; A sample of earlier Vocoder.</ref>

Vocoder effects have been used by musicians in both electronic music and as a special effect, along with more traditional instruments. In 1969, [[Sly and the Family Stone]] used it in "Sex Machine", a song on the album ''[[Stand!]]''. Other artists who have made vocoders an essential part of their music, overall or during an extended phase. Examples include the German [[synthpop]] group [[Kraftwerk]], the Japanese [[New wave music|new wave]] group [[Polysics]], [[Stevie Wonder]] ("[[Send One Your Love]]", "[[A Seed's a Star]]") and jazz/fusion keyboardist [[Herbie Hancock]] during his late 1970s period. In 1982 [[Neil Young]] used a Sennheiser Vocoder VSM201 on six of the nine tracks on ''[[Trans (album)|Trans]]''.<ref name="tompkins">{{cite book
 | last      = Tompkins | first = Dave
 | year      = 2010–2011
 | title     = How to Wreck a Nice Beach: The Vocoder from World War II to Hip-Hop, The Machine Speaks
 | publisher = Melville House
| isbn = 978-1-61219-093-8
 }}</ref> The chorus and bridge of [[Michael Jackson]]'s "[[P.Y.T. (Pretty Young Thing)]]". features a vocoder ("Pretty young thing/You make me sing"), courtesy of session musician [[Michael Boddicker]].

Among the most consistent users of the vocoder in emulating the human voice are [[Daft Punk]], who have used this instrument from their first album ''[[Homework (Daft Punk album)|Homework]]'' (1997) to their latest work ''[[Random Access Memories]]'' (2013) and consider the convergence of technological and human voice "the identity of their musical project".<ref>{{cite news
 | title     = Daft Punk: "La musique actuelle manque d'ambition"
 | url       = http://www.lefigaro.fr/musique/2013/05/03/03006-20130503ARTFIG00588-daft-punk-la-musique-actuelle-manque-d-ambition.php
 | format    = interview
 | date      = May 3, 2013
 | newspaper = [[Le Figaro]]
}}</ref> For instance, the lyrics of "[[Around the World (Daft Punk song)|Around the World]]" (1997) are integrally vocoder-processed, "[[Get Lucky (Daft Punk song)|Get Lucky]]" (2013) features a mix of natural and processed human voices, and "[[Instant Crush]]" (2013) features [[Julian Casablancas]] singing into a vocoder.

===Voice effects in other arts===
{{See also|Robotic voice effects}}

Robot voices became a recurring element in popular music during the 20th century. Apart from vocoders, several other methods of producing variations on this effect include: the [[Sonovox]], [[Talk box]], [[Auto-Tune]],<ref group="media" name="T-Pain" /> linear prediction vocoders, [[speech synthesis]],<ref group="media" name="Speech Synthesis" /><ref group="media" name="Speak & Spell" /> [[ring modulation]] and [[comb filter]].

{{listen
| filename     = Vocoder demo.ogg
| title        = Example of vocoder
| description  = Demonstration of the "robotic voice" effect found in film and television
}}
Vocoders are used in [[television production]], [[filmmaking]] and games, usually for robots or talking computers. The robot voices of the [[Cylon (1978)|Cylons]] in ''[[Battlestar Galactica (1978 TV series)|Battlestar Galactica]]'' were created with an EMS Vocoder 2000.<ref name=tompkins /> The [[Doctor Who theme#History|1980 version]] of the ''[[Doctor Who]]'' theme, as arranged and recorded by [[Peter Howell (musician)|Peter Howell]], has a section of the main melody generated by a Roland SVC-350 vocoder. A similar [[Roland VP-330]] vocoder was used to create the voice of [[Soundwave (Transformers)|Soundwave]], a character from the ''[[Transformers]]'' series.

==See also==
* [[Audio time stretching and pitch scaling]]
* [[List of vocoders]]
* [[Silent speech interface]]

==Notes==
{{Notelist}}

==References==
{{Reflist}}

;Multimedia references
{{Reflist|group=media|refs=
<ref group="media" name="T-Pain">{{cite AV media
 | people    = T-Pain
 | title     = I'm Sprung
 | url       = https://www.youtube.com/watch?v=hwzOWFqsa0Q#t=0m50s
 | medium    = CD Single/Download
 | date      = 2005
 | publisher = Jive Records
}}&nbsp; (A sample of [[Auto-Tune]] effect (a.k.a. ''[[T-Pain effect]]'').)</ref>
<ref group="media" name="Speech Synthesis">{{cite AV media
 | title     = Earlier Computer Speech Synthesis
 | url       = https://www.youtube.com/watch?v=ebK4wX76RZ4
 | medium    = Audio
 | date      = c. 1961
 | publisher = AT&T Bell Labs
}}&nbsp; (A sample of earlier computer-based [[speech synthesis]] and song synthesis, by [[John Larry Kelly, Jr.]] and [[Louis Gerstman]] at [[Bell Labs]], using [[IBM 704]] computer. The demo song "[[Daisy Bell]]", musical accompanied by [[Max Mathews]], impressed [[Arthur C. Clarke]] and later he used it in the climactic scene of the screenplay for his novel ''[[2001: A Space Odyssey (novel)|2001: A Space Odyssey]]''.)</ref>
<ref group="media" name="Speak & Spell">{{cite AV media
 | title     = TI Speak & Spell
 | url       = https://www.youtube.com/watch?v=qM8FcN0aAvU
 | medium    = Video |date=c. 1980
 | publisher = Texas Instruments
}}&nbsp; (A sample of [[speech synthesis]].</ref> [[ring modulation]] and [[comb filter]].)
}}

==External links==
{{Commons category|Vocoders}}
* {{cite web |url=http://www.paia.com/ProdArticles/vocodwrk.htm |title=How Vocoders Work |publisher=PAIA |archive-date=2011-09-07 |archive-url=https://web.archive.org/web/20110907154842/http://www.paia.com/ProdArticles/vocodwrk.htm |url-status=dead}}
* [http://120years.net/the-voder-vocoderhomer-dudleyusa1940/ Description, photographs, and diagram for the vocoder at 120years.net]
* [https://web.archive.org/web/20061209035536/http://digitalmedia.oreilly.com/pub/a/oreilly/digitalmedia/2006/03/29/vocoder-tutorial-and-tips.html O'Reilly Article on Vocoders]
* [https://www.newyorker.com/tech/annals-of-technology/object-interest-vocoder Object of Interest: The Vocoder The New Yorker Magazine mini documentary]

{{Authority control}}

[[Category:Audio effects]]
[[Category:Electronic musical instruments]]
[[Category:Music hardware]]
[[Category:Lossy compression algorithms]]
[[Category:Speech codecs]]
[[Category:Robotics engineering]]