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Vocoders
A vocoder (, a portmanteau of ''vo''ice and en''coder'') 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. The d ... [...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 needed 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 Laboratories ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voder
400px, Schematic circuit of the VODER The Bell Telephone Laboratory's Voder (abbreviation of 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kraftwerk Vocoder Custom Made In Early1970s
Kraftwerk (, ) is a German electronic band formed in Düsseldorf in 1970 by Ralf Hütter and Florian Schneider. Widely considered innovators and pioneers of electronic music, Kraftwerk was 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 1973 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, follo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vocal Cords
In humans, the vocal cords, also known as vocal folds, are folds of throat tissues that are key in creating sounds through Speech, vocalization. The length of the vocal cords affects the pitch of voice, similar to a violin string. Open when breathing and vibrating for speech or singing, the folds are controlled via the recurrent laryngeal nerve, recurrent laryngeal branch of the vagus nerve. They are composed of twin infoldings of mucous membrane stretched horizontally, from back to front, across the larynx. They vibration, vibrate, modulating the flow of air being expelled from the lungs during phonation. The 'true vocal cords' are distinguished from the 'false vocal folds', known as vestibular folds or ''ventricular folds'', which sit slightly superior to the more delicate true folds. These have a minimal role in normal phonation, but can produce deep sonorous tones, screams and growls. The length of the vocal fold at birth is approximately six to eight millimeters and grows t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Envelope Detector
An envelope detector (sometimes called a peak detector) is an electronic circuit that takes a (relatively) high-frequency signal as input and outputs the '' envelope'' of the original signal. Diode detector A simple form of envelope detector used in detectors for early radios is the diode detector. Its output approximates a voltage-shifted version of the input's upper envelope. Between the circuit's input and output is a diode that performs half-wave rectification, allowing substantial current flow only when the input voltage is around a diode drop higher than the output terminal. The output is connected to a capacitor of value C and resistor of value R in parallel to ground. The capacitor is charged as the input voltage approaches its positive peaks. At other times, the capacitor is gradually discharged through the resistor. The resistor and capacitor form a 1st-order low pass filter, which attenuates higher frequencies at a rate of -6 dB per octave above its cu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency Bands
Spectral bands are regions of a given spectrum, having a specific range of wavelengths or frequencies. Most often, it refers to electromagnetic bands, regions of the electromagnetic spectrum. More generally, spectral bands may also be means in the spectra of other types of signals, e.g., noise spectrum. A frequency band is an interval in the frequency domain, limited by a lower frequency and an upper frequency. For example, it may refer to a ''radio band'', such as wireless communication standards set by the International Telecommunication Union. In nuclear physics In nuclear physics, spectral bands refer to the electromagnetic emission of polyatomic systems, including condensed materials, large molecules, etc. Each ''spectral line'' corresponds to the difference in two energy levels of an atom. In molecules, these levels can split. When the number of atoms is large, one gets a continuum of energy levels, the so-called ''spectral bands''. They are often labeled in the same w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Envelope (waves)
In physics and engineering, the envelope of an oscillating signal is a smooth curve outlining its extremes. The envelope thus generalizes the concept of a constant amplitude into an instantaneous amplitude. The figure illustrates a modulated sine wave varying between an ''upper envelope'' and a ''lower envelope''. The envelope function may be a function of time, space, angle, or indeed of any variable. In beating waves A common situation resulting in an envelope function in both space ''x'' and time ''t'' is the superposition of two waves of almost the same wavelength and frequency: : \begin F(x, \ t) & = \sin \left[ 2 \pi \left( \frac - ( f + \Delta f )t \right) \right] + \sin \left[ 2 \pi \left( \frac - ( f - \Delta f )t \right) \right] \\[6pt] & \approx 2\cos \left[ 2 \pi \left( \frac - \Delta f \ t \right) \right] \ \sin \left[ 2 \pi \left( \frac - f \ t \right) \right] \end which uses the trigonometric formula for the Trigonometric identity#Product-to-sum an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectral Energy Distribution
A spectral energy distribution (SED) is a plot of energy versus frequency or wavelength of light (not to be confused with a 'spectrum' of flux density vs frequency or wavelength). It is used in many branches of astronomy to characterize astronomical sources. For example, in radio astronomy they are used to show the emission from synchrotron radiation, free-free emission and other emission mechanisms. In infrared astronomy, SEDs can be used to classify young stellar objects. Detector for spectral energy distribution The count rates observed from a given astronomical radiation source have no simple relationship to the flux from that source, such as might be incident at the top of the Earth's atmosphere. This lack of a simple relationship is due in no small part to the complex properties of radiation detectors. These detector properties can be divided into *those that merely attenuate the beam, including *#residual atmosphere between source and detector, *#absorption in the d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plosive
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. "Stop" refers to the stopping of the airflow, "occlusive" to the articulation which occludes (blocks) the vocal tract, and "plosive" to the plosion (release burst) of the consonant. Some object to the use of "plosive" for inaudibly released stops, which may then instead be called "applosives". The International Phonetic Association and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unvoiced
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 voice (phonetics), voicing and that voicelessness is the lack of phonation. The International Phonetic Alphabet (IPA) has distinct letters for many voiceless and modal voice, 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 nasal consonant, nasals that are voiced in most of the world's languages. However, in some languages sonorants may be voiceless, ... [...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, or when the sound source is mostly non-harmonic, as in whispering and vocal fry. 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 reinforc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
