A vocoder is a category of voice codec that analyzes and synthesizes the human voice signal for audio data compression, voice encryption or voice transformation. The vocoder was invented in 1938 by Homer Dudley at Bell Labs as a means of synthesizing human speech; this work was developed into the channel vocoder, used as a voice codec for telecommunications for coding speech to conserve 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 been used extensively as an electronic musical instrument; the decoder portion of the vocoder, called a voder, can be used independently for speech synthesis.
The human voice consists of sounds generated by the opening and closing of the glottis by the vocal cords, which produces a periodic waveform with many harmonics. This basic sound is filtered by the nose and throat to produce differences in harmonic content 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 the mouth in different fashions; the vocoder examines speech by measuring. This results in a series of signals representing these modified frequencies at any particular time as the user speaks. In simple terms, the signal is split into a number of frequency bands and the level of signal present at each frequency band gives the instantaneous representation of the spectral energy content. To recreate speech, the vocoder reverses the process, processing a broadband noise source by passing it through a stage that filters the frequency content based on the recorded series of numbers.
In the encoder, the input is passed through a multiband filter each band is passed through an envelope follower, the control signals from the envelope followers are transmitted to the decoder. The decoder applies these control signals to corresponding amplifiers of the filter channels for re-synthesis. Information about the instantaneous frequency of the original voice signal is discarded, 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. The vocoder process sends only the parameters of the vocal model over the communication link, instead of a point-by-point recreation of the waveform. Since the parameters change 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 cable. Analog vocoders analyze an incoming signal by splitting the signal into a number of tuned frequency bands or ranges.
A modulator and carrier signal are sent through a series of these tuned bandpass filters. In the example of a typical robot voice, the modulator is a microphone and the carrier is noise or a sawtooth waveform. There are between eight and 20 bands; the amplitude of the modulator for each of the individual analysis bands generates a voltage, 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.. 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 f, ch or any other sibilant sound; these can be mixed with the carrier output to increase clarity. The result is recognizable speech. Vocoders include a second system for generating unvoiced sounds, using a noise generator instead of the fundamental frequency.
In the channel vocoder algorithm, among the two components of an analytic signal, considering only the amplitude component and ignoring the phase component tends to result in an unclear voice. The development of a vocoder was started in 1928 by Bell Labs engineer Homer Dudley, granted patents for it, US application 2,151,091 on March 21, 1939, US application 2,098,956 on Nov 16, 1937. To show the speech synthesis ability of its decoder part, the Voder, was introduced to the public at the AT&T building at the 1939–1940 New York World's Fair; the Voder consisted of a switchable pair of electronic oscillator and noise generator as a sound source of pitched tone and hiss, 10-band resonator filters with variable-gain amplifiers as a vocal tract, the manual controllers including a set of pressure-sensitive keys for filter control, a foot pedal for pitch control of tone. The filters controlled by keys convert the tone and the hiss into vowels and inflections; this was a complex machine to operate.
Dudley's vocoder was used in the SIGSALY system, built by Bell Labs engineers in 1
Arthur W. Robinson was an English first-class cricketer who played seven games with little success, he played rugby league for Hull Kingston Rovers as a centre. Robinson's debut was in South Africa in January 1906, when he appeared for Natal against Marylebone Cricket Club at Pietermaritzburg, scoring 4 and 0, he did not appear in first-class cricket again until after the First World War, playing for Worcestershire against Hampshire in May 1920. He fared little better than he had 14 years earlier, making 2* and 4. Another sizeable gap followed before Robinson, by now in his mid-forties, played five more times for Worcestershire in 1925 and 1926. Once again, however, he failed to make the most of his opportunity and his highest score was 37 against Yorkshire in the first of these games in July 1925. Arthur W. Robinson played right-centre, i.e. number 3, in Hull Kingston Rovers's 0-6 defeat by Warrington in the 1905 Challenge Cup Final during the 1904–05 season at Headingley Rugby Stadium, Leeds on Saturday 29 April 1905, in front of a crowd of 19,638.
Statistical summary from CricketArchive Lists of matches and detailed statistics from CricketArchive Arthur W. Robinson at ESPNcricinfo
Ephraim Rubenstein is a noted American representational painter and teacher. Rubenstein began studying art in the painting group of David Levine and Aaron Shikler, as well as in the studio of Andrew Reiss. In 1977–78 he won a Brooklyn Arts and Cultural Association high school scholarship to the Brooklyn Museum Art School, where he studied with Francis Cunningham, he graduated from Columbia University with a BA in Art History, in 1978, from Columbia University School of the Arts with a MF. A. in Painting, in 1986. From 1987 to 1998, he taught at University of Richmond, the Rhode Island School of Design and the Maryland Institute College of Art, he subsequently studied at the Art Students League of New York with Robert Beverly Hale and Francis Cunningham, at the National Academy of Design school with Harvey Dinnerstein. From 1986-1997, he showed at Tibor de Nagy Gallery, he exhibited subsequently at George Billis Gallery in Chelsea. He has exhibited internationally, with numerous works exhibited as part of the US State Department's Art in Embassies Program.
Rubenstein is a frequent contributor to American Artist, American Artist Drawing and The Artist’s Magazine. Rubenstein has been an influential teacher. From 1987 to 1998, he taught at University of Richmond at the Rhode Island School of Design, the Maryland Institute College of Art, the National Academy of Design School, he teaches at the Art Students League of New York, Columbia University, Department of Narrative Medicine. He is represented by Maurine Littleton Gallery. "Ephraim Rubenstein: Painting from Observation," in Art Students League of New York on painting: lessons and meditations on mediums and methods. Watson Guptill Publications. 2015. ISBN: 9780385345439, his painting, Self-portrait with Books, is in The Metropolitan Museum of Art. Https://ephraimrubenstein.com/ http://www.asllinea.org/ephraim-rubenstein-american-arts-quarterly/ http://www.thequickeningimage.com/Site_4/EPHRAIM.html https://www.theartleague.org/school/faculty_desc.php?teacher_id=2801