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Vocoder
A vocoder (, a portmanteau of ''voice'' and ''encoder'') is a category of speech coding that analyzes and 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. This work was developed into the channel vocoder which was used as a voice codec for telecommunications for speech coding 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 also been used extensively as an electronic musical instrument. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voder
The Bell Telephone Laboratory's Voder (from ''Voice Operating Demonstrator'') was the first attempt to electronically synthesize human speech by breaking it down into its acoustic components. It was invented by Homer Dudley in 1937–1938 and developed on his earlier work on the vocoder. The quality of the speech was limited; however, it demonstrated the synthesis of the human voice, which became one component of the vocoder used in voice communications for security and to save bandwidth.Ben Gold, Nelson Morgan, Dan Ellis, ''Speech and Audio Signal Processing: Processing and Perception of Speech and Music''. John Wiley & Sons, 2011; , pages 9‒13 The Voder synthesized human speech by imitating the effects of the human vocal tract. The operator could select one of two basic sounds by using a wrist bar. A buzz tone generated by a relaxation oscillator produced the voiced vowels and nasal sounds, with the pitch controlled by a foot pedal. A hissing noise produced by a white noi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kraftwerk Vocoder Custom Made In Early1970s
Kraftwerk (, "power station") is a German band formed in Düsseldorf in 1970 by Ralf Hütter and Florian Schneider. Widely considered innovators and pioneers of electronic music, Kraftwerk were among the first successful acts to popularize the genre. The group began as part of West Germany's experimental krautrock scene in the early 1970s before fully embracing electronic instrumentation, including synthesizers, drum machines, and vocoders. Wolfgang Flür joined the band in 1974 and Karl Bartos in 1975, expanding the band to a quartet. On commercially successful albums such as ''Autobahn'' (1974), '' Trans-Europe Express'' (1977), ''The Man-Machine'' (1978), and '' Computer World'' (1981), Kraftwerk developed a self-described "robot pop" style that combined electronic music with pop melodies, sparse arrangements, and repetitive rhythms, while adopting a stylized image including matching suits. Following the release of ''Electric Café'' (1986), Flür left the group in 1987 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speech Coding
Speech coding is an application of data compression of digital audio signals containing speech. Speech coding uses speech-specific parameter estimation using audio signal processing techniques to model the speech signal, combined with generic data compression algorithms to represent the resulting modeled parameters in a compact bitstream. Some applications of speech coding are mobile telephony and voice over IP (VoIP). The most widely used speech coding technique in mobile telephony is linear predictive coding (LPC), while the most widely used in VoIP applications are the LPC and modified discrete cosine transform (MDCT) techniques. The techniques employed in speech coding are similar to those used in audio data compression and audio coding where knowledge in psychoacoustics is used to transmit only data that is relevant to the human auditory system. For example, in voiceband speech coding, only information in the frequency band 400 to 3500 Hz is transmitted but the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formant
In speech science and phonetics, a formant is the broad spectral maximum that results from an acoustic resonance of the human vocal tract. In acoustics, a formant is usually defined as a broad peak, or local maximum, in the spectrum. For harmonic sounds, with this definition, the formant frequency is sometimes taken as that of the harmonic that is most augmented by a resonance. The difference between these two definitions resides in whether "formants" characterise the production mechanisms of a sound or the produced sound itself. In practice, the frequency of a spectral peak differs slightly from the associated resonance frequency, except when, by luck, harmonics are aligned with the resonance frequency. A room can be said to have formants characteristic of that particular room, due to its resonances, i.e., to the way sound reflects from its walls and objects. Room formants of this nature reinforce themselves by emphasizing specific frequencies and absorbing others, as exploit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electronic Musical Instrument
An electronic musical instrument or electrophone is a musical instrument that produces sound using electronic circuitry. Such an instrument sounds by outputting an electrical, electronic or digital audio signal that ultimately is plugged into a power amplifier which drives a loudspeaker, creating the sound heard by the performer and listener. An electronic instrument might include a user interface for controlling its sound, often by adjusting the pitch, frequency, or duration of each note. A common user interface is the musical keyboard, which functions similarly to the keyboard on an acoustic piano, except that with an electronic keyboard, the keyboard itself does not make any sound. An electronic keyboard sends a signal to a synth module, computer or other electronic or digital sound generator, which then creates a sound. However, it is increasingly common to separate user interface and sound-generating functions into a music controller ( input device) and a music synt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voice Encryption
Secure voice (alternatively secure speech or ciphony) is a term in cryptography for the encryption of voice communication over a range of communication types such as radio, telephone or IP. History The implementation of voice encryption dates back to World War II when secure communication was paramount to the US armed forces. During that time, noise was simply added to a voice signal to prevent enemies from listening to the conversations. Noise was added by playing a record of noise in sync with the voice signal and when the voice signal reached the receiver, the noise signal was subtracted out, leaving the original voice signal. In order to subtract out the noise, the receiver need to have exactly the same noise signal and the noise records were only made in pairs; one for the transmitter and one for the receiver. Having only two copies of records made it impossible for the wrong receiver to decrypt the signal. To implement the system, the army contracted Bell Laborato ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homer Dudley
Homer W. Dudley (14 November 1896– 18 September 1980) was a pioneering electronic and acoustic engineer who created the first electronic voice synthesizer for Bell Labs in the 1930s and led the development of a method of sending secure voice transmissions during World War Two. His awards include the Franklin Institute's Stuart Ballantine Medal (1965). Early life Born in Virginia, Dudley's family moved to Pennsylvania when he was a schoolboy. His father was a preacher, and his parents also gave lessons to students, in classical and religious subjects. Dudley trained to be a grade school and high school teacher. He found it difficult to keep discipline in the classroom and soon gave up teaching. Intending a change in career, he enrolled in Pennsylvania State University, where he developed an interest in the nascent science of electronic engineering. After taking some college courses in electronic engineering, Dudley found employment with Bell Laboratories, which was at that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stop Consonant
In phonetics, a plosive, also known as an occlusive or simply a stop, is a pulmonic consonant in which the vocal tract is blocked so that all airflow ceases. The occlusion may be made with the tongue tip or blade (, ), tongue body (, ), lips (, ), or glottis (). Plosives contrast with nasals, where the vocal tract is blocked but airflow continues through the nose, as in and , and with fricatives, where partial occlusion impedes but does not block airflow in the vocal tract. Terminology The terms ''stop, occlusive,'' and ''plosive'' are often used interchangeably. Linguists who distinguish them may not agree on the distinction being made. The terms refer to different features of the consonant. "Stop" refers to the airflow that is stopped. "Occlusive" refers to the articulation, which occludes (blocks) the vocal tract. "Plosive" refers to the release burst (plosion) of the consonant. Some object to the use of "plosive" for inaudibly released stops, which may then instead ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voiceless Consonant
In linguistics, voicelessness is the property of sounds being pronounced without the larynx vibrating. Phonologically, it is a type of phonation, which contrasts with other states of the larynx, but some object that the word phonation implies voicing and that voicelessness is the lack of phonation. The International Phonetic Alphabet has distinct letters for many voiceless and modally voiced pairs of consonants (the obstruents), such as . Also, there are diacritics for voicelessness, and , which is used for letters with a descender. Diacritics are typically used with letters for prototypically voiced sounds, such as vowels and sonorant consonants: . In Russian use of the IPA, the voicing diacritic may be turned for voicelessness, e.g. . Voiceless vowels and other sonorants Sonorants are sounds such as vowels and nasals that are voiced in most of the world's languages. However, in some languages sonorants may be voiceless, usually allophonically. For example, the Japan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communication Channel
A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for information transfer of, for example, a digital bit stream, from one or several '' senders'' to one or several '' receivers''. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second. Communicating an information signal across distance requires some form of pathway or medium. These pathways, called communication channels, use two types of media: Transmission line (e.g. twisted-pair, coaxial, and fiber-optic cable) and broadcast (e.g. microwave, satellite, radio, and infrared). In information theory, a channel refers to a theoretical ''channel model'' with certain error characteristics. In this more general view, a storage device is also a communication cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Band-pass Filter
A band-pass filter or bandpass filter (BPF) is a device that passes frequencies within a certain range and rejects ( attenuates) frequencies outside that range. Description In electronics and signal processing, a filter is usually a two-port circuit or device which removes frequency components of a signal (an alternating voltage or current). A band-pass filter allows through components in a specified band of frequencies, called its ''passband'' but blocks components with frequencies above or below this band. This contrasts with a high-pass filter, which allows through components with frequencies above a specific frequency, and a low-pass filter, which allows through components with frequencies below a specific frequency. In digital signal processing, in which signals represented by digital numbers are processed by computer programs, a band-pass filter is a computer algorithm that performs the same function. The term band-pass filter is also used for optical filter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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