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Dictionary of Audio Terminology - J

j - The symbol for the imaginary number , i.e., a number representing the square root of -1. See: complex number. [A lower case "i" is also used in mathematics but not in electronics since "i" is the symbol for current.]

J - The symbol for joule, the SI unit of energy or work.

jabber - To talk rapidly, unintelligibly, or idly. To utter rapidly or unintelligibly. Rapid or babbling talk. [AHD]

Jacket - The insulating layer of material that surrounds a wire or cable offering protection; also called sheath.

jackfield - British term for patchbay.

Jack Mullin - (b. 1913–1999) American who pioneered modern tape recording based on his discovery of the first German tape recorders during WWII.

jacks and plugs - Common name for audio connectors, where jack = female and plug = male is the standard convention for 1/4" and RCA -- only -- not followed for other types of connectors. If a connector is on the end of a cable -- XLR and others -- then either sex is a plug.

Jackson, Bruce - (b. 1948-2011) Australian audio engineering sound pioneer who did live sound for Elvis Presley, Bruce Springsteen, Barbara Streisand and others. He started out cofounding JANDS and went on to invent and develop many digital audio innovations.

Jacob's ladder (aka high voltage traveling arc) - "The spark gap is formed by two wires, approximately vertical but gradually diverging away from each other towards the top in a narrow "V" shape. It was named for the "ladder to heaven" described in the Bible." [From Wikipedia]

JADE (Joint Audio Decoder Encoder) - Siemens trademark for their device that implements voice compression algorithms.

JAES - Journal of the Audio Engineering Society.

jam session - An informal gathering of musicians to play improvised or unrehearsed music. [AHD]

jam sync - (1) The process of regenerating SMPTE timecode from an original source. Used for repair as well as for new copies. (2) A recording studio in Nashville specializing in multichannel and multimedia founded by KK Proffitt and Joel Silverman.

James Bullough Lansing - (James Martini, b. 1902-1949) American entrepreneur and inventor most famous for his companies: Lansing Manufacturing, Altec-Lansing and JBL.

James T. Russell - American physicist who came up with a CD concept in 1965 that he licensed to Sony in 1970.

jamming - The wedging of cables in a conduit when three cables lie side by side in a flat plane. [IEEE Std 576]

JANDS - Famous pro audio, lighting and staging company, which started out as a distributor in Australia.

jangle - To make a harsh metallic sound: The spurs jangled noisily. [AHD]

jangle pop The first and most famous jangle pop band was The Byrds.

Janovsky, W. - German engineer responsible for one of the earliest papers on non-linear distortion thresholds as published in his 1929 paper: "The Audibility of Distortion (in German language), Elek. Nachr.-Tech., vol. 6, pp. 421-439 (Nov., 1929).

jansky Abbr. Jy - A unit of spectral power flux density: 10-26 times one watt per square meter per Hertz (IEEE Std 211).

JASA - Journal of the Acoustical Society of America.

jass - Jazz music, written both ways from 1913 up until around 1920, when the word "jazz" became the accepted spelling. [Decharne]

Jawaiian - A reggae genre combining traditional Hawaiian and Jamaican styles.

JavaTM - The trademarked name for a powerful object-oriented programming language developed by Sun Microsystems. Java allows high-speed fully interactive Web pages to be developed for the Internet or any type of platform.

Jazz A style of music, native to America, characterized by a strong but flexible rhythmic understructure with solo and ensemble improvisations on basic tunes and chord patterns and, more recently, a highly sophisticated harmonic idiom. [AHD]

Jecklin disk - Official name, after inventor Jürg Jecklin, the former Swiss Radio chief sound engineer, for placing a baffle between two microphones in an AB setup.

JEDEC (Joint Electron Device Engineering Council) - Standards creating body for the microelectronics industry.

Jeep Harned - During the late 1950s Grover 'Jeep' Harned, the founder of MCI, owned and operated a small record and stereo servicing outlet in Ft. Lauderdale, Florida. He also built some custom audio equipment at the request of customers. Mack Emerman, the owner of the nearby Criteria Recording Studios asked Harned to build some electronics for some Ampex tape recorders and mixing consoles.

Harned supplied a growing list of customers with custom designed and builded mixing consoles, audio preamplifiers and general record electronics. Harned's expanding list of record industry contacts led to regular referrals to build mixing consoles as well as some long term service contracts. In addition he installed commercial sound systems for the Parker Playhouse, Pirate's Worlds and Fort Lauderdale International Airport amongst others. Consequently in 1965 Harned established the company Music Center Incorporated

JEITA (Japan Electronics and Information Technology Industries Association) - A trade organization for the electronics and IT industries.

jellyfish display - A type of metering used to display multichannel surround sound characteristics, i.e., usually the relative amplitude between channels; so-called for its roundish changing jellyfish-like pattern.

Jerk - The (first) derivative of acceleration, i.e., it is a measure of the rate of change of acceleration -- just as velocity is the derivative of speed, and acceleration is the derivative of velocity.

jerking or jerkin' - Originated in Los Angeles, it is a dance movement consisting of rapidly moving your legs in and out, as well as other complicated moves.

jew's harp - A small musical instrument consisting of a lyre-shaped metal frame that is held between the teeth and a projecting steel tongue that is plucked to produce a soft twanging sound. [AHD]

JFET (junction field-effect transistor) - The simplest type of field-effect transistor. It can be used as an electronically-controlled switch or as a voltage-controlled resistance. Electric charge flows through a semiconducting channel between "source" and "drain" terminals. By applying a bias voltage to a "gate" terminal, the channel is "pinched", so that the electric current is impeded or switched off completely. [Wikipedia]

Jiffy - An actual unit of time, representing 1/100th of a second.

Jig -Any of various lively dances in triple time. The music for such a dance. Also called gigue. [AHD]

jiggumbob - A trinket; a knick-knack; a slight contrivance in machinery. [Lynch]

Jim Williams - (b. 1948-2011) American engineer, analog IC guru, and cofounder of Linear Technology.

jinghu - Chinese bowed 2-stringe fiddle.

jingle - Noun (1) The sound produced by or as if by bits of metal striking together. (2) A piece of light singsong verse or rhyme. (3) A catchy, often musical advertising slogan. Verb (1) To make a tinkling or ringing metallic sound. (2) To have the catchy sound of a simple, repetitious rhyme or doggerel. To cause to make a tinkling or ringing metallic sound. [AHD]

JIRA - Popular software development tool that eases bug tracking, issue tracking and project management.

JITC (Joint Interoperability Test Command) - A military compatibility testing organization.

jitter - A tendency towards lack of synchronization caused by electrical changes. Technically the unexpected (and unwanted) phase shift of digital pulses over a transmission medium. Time skew; a discrepancy between when a digital edge transition is supposed to occur and when it actually does occur.

jitter timing error - Short-term deviations of the transitions of a digital signal from their ideal positions in time.

jnd (just noticeable difference) - In reference to physiology, the smallest difference in a sensory input detectable by a human being.

John T. "Jack" Mullin - (b. 1913–1999) American who pioneered modern tape recording based on his discovery of the first German tape recorders during WWII.

Johnson noise or thermal noise - A form of white noise resulting from thermal agitation in electronic components. For example, a simple resistor hooked up to nothing generates noise, and the larger the resistor value the greater the noise. It is called thermal noise or Johnson noise and results from the motion of electron charge of the atoms making up the resistor (called thermal agitation, which is caused by heat - the hotter the resistor, the noisier. [After John Bertrand Johnson (b. 1887-1970), Swedish-born American physicist who first observed thermal noise while at Bell Labs in 1927, publishing his findings as "Thermal agitation of electricity in conductors," Phys. Rev., vol. 32, pp. 97-109, 1928.]

John William Strutt - Rayleigh, Lord (b. 1842-1919) British physicist. He won a 1904 Nobel Prize for investigating the density of gases and for discovering argon with Sir William Ramsay.

joint probability - The likelihood that two or more things will occur together.

Jones, R.G. - Founded in 1926, near London by Reginald Geoffrey Jones, the RG Jones company, along with Swanson Sound Service (Oakland, CA) are considered the first sound companies, and both are still going strong.

Joplin, Scott - (1867-1917) American musician and composer of ragtime music.

joule - Abbr. J or j - (1) The International System unit of electrical, mechanical, and thermal energy. (2) (a) A unit of electrical energy equal to the work done when a current of one ampere is passed through a resistance of one ohm for one second. (b) A unit of energy equal to the work done when a force of one newton acts through a distance of one meter. [AHD]

Joule, James Prescott - (b. 1818-1889) British physicist who established the mechanical theory of heat and discovered the first law of thermodynamics: a form of the law of conservation of energy whose discovery he shared with Hermann von Helmholtz, Julius von Mayer and Lord Kelvin. [AHD]

Joule's Law - It was James Prescott Joule (see above) who came up with (and published in 1841) the basic power equations P = I2R; P = IE; & P = E2/R, NOT Georg Simon Ohm as is commonly believed.

joystick - In reference to potentiometer/encoders, a type of potentiometer or digital encoder with movement over two axes (sometimes three with the third being in-out, z-axis). [This is also called two or three degrees of freedom]. Usually the axis are left-right, x-axis, and up-down (or away-toward), y-axis, with each controlling a separate potentiometer or encoder. The term is borrowed from aviation technology meaning an aircraft control stick.

JPEG (Joint Photographic Experts Group) - A standard for lossy compression of graphic-image files.

JSA (Japanese Standards Association) - The National Standards organization responsible for coordinating standards preparation in Japan.

jùjú - A style of NIgerian popular music featuring electric guitars and traditional drums. [AHD]

julian date - A chronological year date system where the days are sequentially numbered beginning with January 1, 4713 BC, Greenwich noon.

jump cut - An edit between two video shots or audio sound bites that creates a "jump" or break in continuity.

jumper - A conductor placed across the clear space between the ends of two conductors, or to connect conductors on different layers, on a printed circuit board.

Junction - The transition boundary between semiconductor regions of different electrical properties (e.g., n-n+, p-n, p-p+ semiconductors, or between a metal and a semiconductor). [IEEE]

junction, rectifying - A region between two materials, typically n-type or p-type semiconductors, or between a metal and a semiconductor, arranged to provide a very low resistance to current flow in one direction and a very high resistance to current flow in the opposite direction. [IEEE]

just intonation or just temperament - A musical scale employing frequency intervals represented by the ratios of the smaller integers of the harmonic series. [Olson]

just noticeable difference (jnd) - The smallest difference in a sensory input detectable by a human being.

justify - To shift a numeral so that the most significant digit, or the least significant digit, is placed at a specific position in a row.

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HistoryOfRecording.com acknowledges the Elsevier, Inc. publication, Audio Engineering know it all, the University of Washington Press publication, The Audio Dictionary, second edition, the Howard W. Sames & Co., Inc. publication, Audio cyclopedia, the Cambridge University Press publication, The Art of Electronics, Rane Corporation (Dennis A. Bohn, CTO), Houghton Mifflin Company publication, The American Heritage Dictionary of the English Language, Fourth Edition, the IEEE publication, IEEE 100: The Authoritative Dictionary of IEEE Standards Terms, Seventh Edition and Wikipedia in the preparation of this Dictionary of Audio Terminology.

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